MGSS
KSEEB - SSLC SCIENCE MODELS QUESTION PAPER – 1(2021-22)
Sub: Science Sub. Code: 83E Time: 3.15 Hour Max Marks: 80
PART A: PHYSICS
I Four alternatives are given for each of the following questions / incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 2x1=2
1. The diameter of the reflecting surface of spherical mirror is
A) Optical Centre B) Centre of Curvature C) Aperture D) Principal axis
Ans: C) Aperture
2. An electric motor takes 5A from a 220V electric source. The power of the motor is
A) 1100W B) 44W C) 225W D) 440W
Ans: A) 1100W
II Answer the following questions. 3x1=3
3. If the focal length of a spherical mirror is 15cm. Find the radius of curvature ?
Ans: R = 2f, R = 2×15, R = 30cm
4. Mention any two disadvantages of fossil fuels.
Ans:
- Fossil fuels are not renewable energy sources
- Fossil fuels pollute the environment.
5. What is an electric circuit ?
Ans: A continuous and closed path of an electric current is called an electric circuit.
III Answer the following questions. 3x2=6
6. How does overloading and short-circuit occur in an electric circuit? Explain. What is the function of a fuse during this situation ?
Ans: The over usage of electricity in a circuit more than its limit is called overload. In other words, the rising of electric load in a circuit is called overload. The live wire and the neutral wire come into direct contact is called short circuit. The function of fuse in these situations is to cut off the rising load.
7. Draw the schematic diagram of a biogas plant.
Ans:
8 An electric lamp whose resistance is 40Ω and conductor of 8Ω resistance are connected in series to 12V battery in an electric circuit. Calculate the total resistance of the circuit and the current flowing through the circuit.
Ans:
In series combination,
- Take a wire, a bar magnet and a galvanometer
- Move the magnet towards the coil of wire.
- The galvanometer moves to indicate a current in the wire.
- When the direction of the magnet is reversed, the current reverses (indicated by the galvanometer needle swaying in the opposite direction)
- When the speed of movement of the magnet changes, the galvanometer deflects faster.
- Moving a magnet towards a coil induces a current in the coil is called electromagnetic induction.
- increasing the rate of rotation.
- increasing the strength of the magnetic field.
- increasing the number of turns on the coil.
- An electric motor is a machine that converts electrical energy to mechanical energy.
- Electric motor follows Fleming’s left-hand rule.
- An electric generator is a machine that converts mechanical energy to electrical energy.
- Electric generator follows Fleming’s right-hand rule
- used as rear view mirror in vehicle
- used in street light
- used in torches and vehicle headlight
- used as shaving mirror
- used in glass, soap and paper industries.
- it is used in removing permanent hardness of water.
- it is used as oxidising agent in many in many chemical industries
- it is used to make drinking water free
- used in water teatment, swimming pool, pestiside
- used as fuel
Ans: The atomic number of elements 12 is Mg and 16 is S both elements are occurs in same period because Mg and S have valence electrons present in 3rd main shell.
The magnesium atom transfers its one electron to each chlorine atom to form an ionic bond.
XI Answer the following questions. 1x5=5
| Saturated hydrocarbons | Unsaturated hydrocarbons |
| Saturated hydrocarbons are the compounds containing only single covalent bonds. These are also known as alkanes. | Unsaturated hydrocarbons are the straight chain compounds containing double or triple covalent bonds. |
| These compounds are less reactive. | These compounds are more reactive. |
| These compounds under go substitution reactions. | These compounds under go addition reactions. |
b) i) C2H5COOH ii) C6H12  |  |
Biodegradable Substances | Non-biodegradable Substances |
They are considered safe for the environment | They are considered harmful to the environment |
Biodegradable substances are natural wastes | Non-biodegradable substances are synthetic wastes |
Biodegradable substances do not cause pollution | Non-biodegradable substances cause pollution |
Mucous: It protecting the stomach lining and gastric pits from the acid.
Digestive enzymes: They are the group of enzymes which functions by breaking down complex substances into simpler substances.
Hydrochloric acid: It destroying harmful microorganisms present in the food particles.
- Genetic drift.
- Natural selection.
- Genetic mutation.
- Geographical isolation.
- Reproductive isolation.
- Environmental factors on the isolated populations.
Key Answer
MGSS
KSEEB - SSLC SCIENCE MODEL QUESTION PAPER – 1(2020-21)
Sub: Science Sub. Code: 83E Time: 3.15 Hour Max Marks: 80
PART A: PHYSICS
I. Four alternatives are given for each of the following questions/incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 3 x 1 = 3
1. The SI unit of electric charges is:
Ans: C. coulomb
2. The suitable focal length of the convex lens used as magnifying lens to read “Hallmark 916’’ written on ornaments is :
A. 12 cm B. 60 cm C. 100 cm D. 120 cm
Ans: A. 12 cm
3. The magnetic field lines inside a solenoid are in the form of parallel straight lines. The reason for this is, the magnetic field inside the solenoid is:
A. very high B. uniform C. zero D. produced by electricity
Ans: B. uniform
II. Answer the following questions. 2 x 1 = 2
4. If the radius of curvature of a lens is 30 cm, then what is its focal length?
Ans:
When radius of curvature , R = 30 cm
then , R = 2f or f = R / 2 or f = 30 /2 so, f = 15 cm
5. In the experiment of refraction through a glass slab, the angle of incidence should be less than 90°. Why?
Ans:
If the rays of light are incident upon the glass surface perpendicularly, or at 90 degree angle to the surface, the rays will pass through without changing direction. In this case, the angle of incidence and angle of refraction are always zero.
III. Answer the following questions. 3 x 2 = 6
6. Draw the ray diagram to show the formation of image by a convex lens when the object is kept between 2F1 and F1 . (F1 : Principal focus of the convex lens)
Ans:
7. The resistivity of two conductors ‘A’ and ‘B’ are 1.62 x 10−8 Ω m and 5.20 x 10−8 Ω m respectively. Which of them is used in :
(i) Transportation of electricity (ii) The making of heating coils? Why?
Ans:
(i) Conductor A
(ii) Conductor B because it's resistivity is more than Conductor A so it will resist more electricity.
8. Observe the following table. Complete the table using Ohm’s law :
Ans:
Ohm's law Formula = V = IR
Where
V = Potential Difference I = Electric Current R = Resistance
i) Given I = 2A V = 120V
To Find Resistance (R)
Formula V=IR 120V = 2A×(R) R = 120V/2A R = 60Ω
ii) Given I = 1.5A R = 60Ω
To Find Potential difference (V)
Formula V= IR V = 1.5×60 V = 90V
(iii) Given V = 60V R = 60Ω
To Find Current (I)
Formula V = IR 60V = I60Ω I = 60/60 I = 1A
IV. Answer the following questions. 3 x 3 = 9
9. Draw the diagram of an electric generator. Label the following parts.
(i) Carbon Brushes (ii) Rings
Ans:
10. Explain the experiment to find out the focal length of a convex lens. The focal length of a convex lens is 100 cm. Find its power.
Ans:
Given that,
Focal length f = 100 cm
We know that,
The power of the lens is the reciprocal of the focal length of the lens.
The power of the lens is
Here, P = power of the lens
f = focal length of the lens
Power =. 1 / focal length (in m)
P =. 1/ 1 m
P = 1 dioptre
OR
An object is kept at a distance of 30 cm from a diverging lens of focal length 15 cm. At what distance the image is formed from the lens? Find the magnification of the image.
Ans:
A concave lens(diverging lens) always forms a virtual, erect image on the same side of the object.
u = -30cm. f = -15cm v=?
1/f= 1/v - 1/u
1/-15= 1/v - 1/-30
-1/v= 1/15 +1/30
-1/v= 2+1/30
-1/v= 3/30
v= -10cm.
magnification= v/u
m= -10/-30 m=0.34
+ ve sign shows that the image is virtual and erect. the image is one third of the object
11. Explain the advantages and disadvantages of solar cells.
Ans:
Advantages of Solar cells | Disadvantages of Solar cells |
· Renewable source of energy · Environment friendly · Easy to maintain. · Very useful in remote locations where there is a power crisis | · Initial setup cost is high.
|
V. Answer the following questions. 2 x 4 = 8
12. Explain the principle of working of simple electric motor. What is the role of split rings in an electric motor? How are commercial motors different from simple electric motor?
Ans:
· The principle of an electric motor is based on the current carrying conductor which produces magnetic field around it. A current carrying conductor is placed perpendicular to the magnetic field so that it experiences a force.
· In electric motors, the splittings acts as a commutator. The reversal of current also reverses the direction of force acting on the two arms AB and CD. The reversing of the current is repeated at each half rotation, giving rise to a continuous rotation of the coil and to the axle.
· In commercial motor an electromagnet is used in place of permanent magnet. Commercial motors have more number of turns of conducting wire in current carrying coil. Commercial motors have soft iron core on which the coil is wound.
OR
Explain the following with reference to the magnetic field around a straight conductor carrying current.
(i) Tracing the pattern of magnetic field
(ii) Increasing the intensity of magnetic field
(iii) Reversing the direction of electric current.
Ans:
(i) Tracing the pattern of magnetic field
The two ways to trace the magnetic field of a bar magnet is by a compass and by iron filings in the compass needle method, the needle rotate freely and trace it. In another way, the iron filings make the magnetic path.
(ii) Increasing the intensity of magnetic field
The strength of the magnetic field around a conductor can be increased by increasing the current.
(iii) Reversing the direction of electric current.
When reverse the direction of the current in the wire, the north and south poles are also reversed. When reverse the current again, the north and south poles reverse again. In fact, each time the current is reversed, the north and south poles will exchange places.
13. a) State Ohm’s law. Mention the factors on which the resistance of a conductor depends.
Ans:
A law stating that electric current is proportional to voltage and inversely proportional to resistance.
Factors on which the resistance of a conductor depends are:
· Length of wire.
· Cross section area or thickness of wire.
· Nature of the material.
· Temperature
Resistance of wire is directly proportional to length and temperature and inversely proportional to cross section area.
b) State Joule’s law of heating and write the mathematical formula of this law.
Ans:
Joule's law of heating states that heat produced when a current of I flows in a wire of resistance R ohms for time t seconds is given by
H = I2Rt.
H =Heat
I =Current
R=Resistance of a conductor
T=Time taken
PART B: CHEMISTRY
VI. Four alternatives are given for each of the following questions/incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 3 x 1 = 3
14. The gas liberated when an acid reacts with a metal is:
A. Hydrogen B. Chlorine C. Carbon dioxide D. Nitrogen dioxide
Ans: A. Hydrogen
15. The hydrocarbon that undergoes addition reaction among the following is :
A. C2 H6 B. C3 H8 C. CH4 D. C3 H6
Ans: D. C3 H6
16. In modern periodic table, as we move from left to right along the period, the atomic size of the elements.
A. increases B. does not change
C. decreases D. first increases and then decreases
Ans: C. decreases
VII. Answer the following questions. 3 x 1 = 3
17. Is it possible to test the hardness of water using detergents? Give reason for your answer.
Ans:
No, because detergent gives lather with hard and soft water both, while a soap gives lather with soft water only. Thus, it is not possible to check if water is hard by using a detergent.
18. in the modern periodic table, the elements of 17th group are Flourine, Chlorine, Bromine, Iodine respectively. Which element has the highest ability to receive electrons? Why
Ans:
Fluorine is more electronegative than other elements because fluorine is smaller and has its electrons closer to the positively charged nucleus. So that fluorine has more tendency to attract shared electrons to itself.
19. Ionic compounds have high melting points. Why?
Ans:
Because the ions are held together tightly by strong forces of attraction between the oppositely charged ions so, it takes a lot of energy to break all the bonds. As a result, ionic compounds have high melting and boiling points.
VIII. Answer the following questions. 3 x 2 = 6
20. Name the Ketone having four carbon atoms and write its structure.
Ans:
Butanone or Ethyl methyl ketone has four carbon atoms.
OR
Explain combustion reaction of carbon compounds with an example.
Ans:
The complete combustion of carbon compounds in the air gives carbon dioxide water, heat and light.
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) + Heat and light
Saturated hydrocarbons burn with a blue flame in the presence of a sufficient supply of air or oxygen. In presence of limited supply of air, saturated hydrocarbon forms a sooty flame.
Unsaturated hydrocarbons burn with a yellow smoky flame.
21. Draw the diagram of the apparatus used to show that acid solution in water conducts electricity and label dilute hydrochloric acid
Ans:
22. The gas liberated when sodium carbonate reacts with dilute hydrochloric acid is passed through lime water, a white precipitate is formed. But when the same gas is passed through lime water in excess, precipitate is not visible. Why?
Ans:
When excess of carbon dioxide is passed through lime water, it makes milky colour of lime water disappear. This happens because of formation of calcium hydrogen carbonate. As calcium hydrogen carbonate is soluble in water, thus, the milky colour of solution mixture disappears.
IX. Answer the following questions. 3 x 3 = 9
23. Explain the limitations of Medeleev’s periodic table.
Ans:
- Elements with large differences in properties were included in the same group.
- No proper position could be given to the element hydrogen.
- The increasing order of atomic mass was not strictly followed throughout. For example in cobalt and nickel & Tellurium and Indium.
- As isotopes are atoms of the same element having different atomic masses, not given different positions while arranging them in the order of atomic mass.
OR
Explain the limitations of Newlands’ law of Octaves.
Ans:
- Law of Octaves only applicable upto calcium and after calcium every 8th did not possess properties similar to that of the first.
- later on , several new elements were discovered, whose properties did not fit into the aw of octaves
- Newlands'law of Octaves worked well with lighter elements only.
24. Write one difference between saturated carbon compounds and unsaturated carbon compounds. Carbon forms covalent bonds with other atoms but not ionic bonds. Why? Explain.
Ans:
Saturated Hydrocarbon | Unsaturated Hydrocarbon |
| |
Contain more hydrogen atoms than the corresponding unsaturated hydrocarbons. | Contain fewer hydrogens than the corresponding saturated hydrocarbon. |
Examples include alkanes and cycloalkanes. | Examples include alkenes, alkynes, and aromatic hydrocarbons. |
They have a relatively low chemical reactivity | They are more reactive than their saturated counterparts. |
They generally burn with a blue flame | They generally burn with a sooty flame. |
Carbon forms covalent bonds because carbon has an atomic number 6 and have 4 electrons in its octet so it can neither lose nor gain 4 electrons to complete it's octet so it forms covalent bonds by sharing it's 4 electrons and covalent bonds are more stronger than the ionic bonds…
25. Draw the diagram of the arrangement of the apparatus showing the reaction of steam on metal. Label the following.
(i) Metal Sample (ii) Delivery tube
Ans:
X. Answer the following question. 1 x 4 = 4
26. a) What are alloys? Name the alloy which has lead and tin as its constituent and write one of its uses.
Ans:
· Alloys are the homogeneous mixture of two or more metals or a non metal.
· Solder is the alloy which has lead and tin as it's constituent .
· One use of solder is used to create electrical joints
b) What is an amphoteric oxide? Write any two chemical properties of metals
ans:
Oxides of metals which have both acidic as well as basic behaviour are known as amphoteric oxides
- Many metals produce metal oxide by burning in the oxygen of the air. Highly reactive metals react violently when they’re burnt in oxygen.
- Metals produce metal oxide and hydrogen gas while reacting with water.
- Soluble metal oxides dissolve in water and create metal hydroxide.
PART C: BIOLOGY
XI. Four alternatives are given for each of the following questions/ incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 2 x 1 = 2
27. The practice of using used materials without changing their shape and form is
A. Reuse B. Recycling C. Repurpose D. Reduce
Ans: A. Reuse
28. The correct statement with respect to biodegradable substances among the following is; these substances
A. remain inert in the environment for a long time
B. harm various organisms in the ecosystem
C. increase the density of harmful chemicals in different tropic levels
D. undergo recycling naturally in the environment
Ans: D. undergo recycling naturally in the environment
XII. Answer the following questions. 3 x 1 = 3
29. How is ozone layer formed in the atmosphere?
Ans:
"It is created when ultraviolet radiation (sunlight) strikes the stratosphere, dissociating or splitting oxygen molecules (02) to atomic oxygen (0). The atomic oxygen quickly combines with further oxygen molecules to form ozone."
30. Forests are called ‘biodiversity hotspots’. Why?
Ans:
Forests are considered 'biodiversity hot spots' because large number of life forms (such as bacteria, fungi, fern, nematodes, insects, birds, reptiles, mammals, gymnosperms and angiosperms) are found there.
31. Mention any two problems caused by the construction of huge dams.
Ans:
- Environmental problem - deforestation leading to loss of biodiversity.
- Social problem - nearby towns and villages becomes homeless.
XIII. Answer the following questions. 2 x 2 = 4
32. The tendrils of pea plants appear to move in a particular direction as they grow. How is this response caused?
Ans:
The growth in a plant part in response to touch is called thigmotropism movement. Such movements are seen in tendrils of climbers. The differential rate of cell division in different parts of the tendril happens due to action of auxin. Auxin move to non-touching cells. The non-touching cells elongate faster to curl around the support stick. A thigmonastic response is a touch response independent of the direction of stimulus.
OR
How does adrenal gland bring the chemical coordination in our body? Explain briefly
Ans:
In case of flight or fight reaction to an emergency situation, Adrenal glands release adrenaline into blood which acts on heart and other tissues causes faster heart beat. more oxygen to muscles reduced blood supply to digestive system and skin diversion of blood to skeletal muscles increase in breathing rate.
33. Draw the diagram showing the longitudinal section of a typical flower and label ‘anther’.
Ans:
XIV. Answer the following questions. 3 x 3 = 9
34. ‘Having two sets of genes in the germ cells is not possible’. Clarify this statement with reasons.
Ans:
In humans, germ cells are haploid in nature or has a single set of genes or chromosomes, 23 in number.
Germ cells are cells of the body, that generates gametes or reproductive units. Germ cells, are generated by the process of meiosis. As a result the set of genes or chromosomes in germ cell are always half to that in the somatic cells.
OR
‘Genetic drift’ and ‘natural selection’ together result in the formation of new species of organisms. How? Explain.
Ans:
Natural selection and genetic drift both result in a change in the frequency of alleles in a population, so both are mechanisms of evolution. Genetic drift causes evolution by random chance due to sampling error, whereas natural selection causes evolution on the basis of fitness.
Natural selection is the process through which populations of living organisms adapt and change. Through this process of natural selection, favorable traits are transmitted through generations. Natural selection can lead to speciation.
35. What is the function of ‘Prostate gland’ and ‘testicles’, in human male reproductive system? What measures can be followed by man to avoid the transfer of sperms into the uterus of a woman?
Ans:
The prostate's most important function is the production of a fluid that, together with sperm cells from the testicles and fluids from other glands, makes up semen.
· Testicles produce male gametes i.e. the sperms and also responsible producing a hormone called testosterone.
· The measures can be followed by man to avoid the transfer of sperms into the uterus of a woman is that using condom.
OR
What is sexual maturation? How does menstruation occur? What is the function of placenta during pregnancy?
Ans:
Sexual maturity is the capability of an organism to reproduce.
Menstruation occurs in cycles. The ovaries prepare an egg for release and the womb prepares a lining to nourish the egg if it is fertilized. When the egg is not fertilised, the lining of the womb is shed and a woman gets her menstrual bleeding.
The placenta is an organ that develops in your uterus during pregnancy. This structure provides oxygen and nutrients to your growing baby and removes waste products from your baby's blood. The placenta attaches to the wall of your uterus, and your baby's umbilical cord arises from it.
36. a) How are the studies of anatomical structures helpful for tracing evolutionary relationships?
Ans:
The anatomical structures and physiological functions of different species provide evidence of evolution. Scientists compare and contrast types of anatomical features, known as homologous structures, vestigial structures, and analogous structures, to figure out how closely related different organisms. Similarities in anatomical structures of different species signify that the two species have a relatively recent common ancestor.
b) How could we determine that ‘the birds are very closely related to reptiles’?
Ans:
- Feather provided insulation to dinosaurs in cold weather. Later in the evolutionary process, feathers were used for flight in birds. Because dinosaurs were reptiles, it means that birds are closely related to reptiles.
- They reproduce by depositing eggs. The laid eggs are coated with calcium.
- Both birds and reptiles breathing process is same that is they breathe via lungs.
- Reptiles have Circulatory system as same like birds. i.e. they have four chambered heart.
XV . Answer the following question. 1 x 4 = 4
37. Draw the diagram showing the longitudinal section of the human brain. Label the following parts. i) Hypothalamus ii) Medulla
Ans:
XVI. Answer the following questions. 1 x 5 = 5
38. a) What are the functions of the fluids `blood’ and `lymph’ in humans? What are the different waste materials added to the urine from the blood?
Ans:
blood
- Regulates the pH by interacting with acids and bases.
- Involved in the transportation of hormones, nutrition, enzymes, respiratory gases and other molecules to the respective parts of the body.
lymph
- Removes metabolic wastes from the tissue cells.
- It helps in invading the entry of pathogenic infections caused by microbes.
Urine is an aqueous solution of greater than 95% water. Other constituents include urea, chloride, sodium, potassium, creatinine and other dissolved ions, and inorganic and organic compounds.
b) How are waste materials excreted in plants?
Ans:
· Excess of water is also excreted from the plant body through the stomatal pores and from the surfaces of fruits and stems. The process of elimination of water is called transpiration.
· The gums, oils, latex, resins, etc. are some waste products stored in plant parts like barks, stems, leaves, etc. Eventually, plants shed off these parts.
· Aquatic plants excrete metabolic wastes through diffusion. Terrestrial plants excrete into the soil.
· Excess carbon dioxide and oxygen are excreted from the plant through the stomata in the leaves.
KSEEB - SSLC SCIENCE MODELS QUESTION PAPER – 2(2020-21)
Sub: Science Sub. Code: 83E Time: 3.15 Hour Max Marks: 80
PART A: PHYSICS
I. Four alternatives are given for each of the following questions/incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 4 x 1 = 4
1. The source of energy in nuclear power reactor is:
A. Nuclear fission reaction B. Exothermic chemical reaction
C. Nuclear fusion reaction D. controlled nuclear fission chain reaction
Ans: A. Nuclear fission reaction
2. Which of the following is NOT a property of magnetic lines?
A. Magnetic field lines are dense near poles
B. Magnetic field lines are closed loops
C. Magnetic field lines intersect each other
D. Magnetic field lines emerge from north pole and merge at the south pole
Ans: C. Magnetic field lines intersect each other
3. The work done in moving a charge of 2C across two points having a potential difference 12V is :
A. 24 J B. 6 J C. 14 J D. 10 J
Ans: A. 24 J
4. The correct way of using electrical appliances in domestic electric circuit is
A. Connecting electrical appliances in series
B. using an electrical appliance of 880 W power in 5A electric circuit
C. Connecting main fuse to electrical appliances in parallel
D. using an electrical appliance of 2 KW power in 5A electric circuit
Ans: C. Connecting main fuse to electrical appliances in parallel
II. Answer the following questions. 2 x 1 = 2
5. State Fleming’s left hand rule.
Ans:
According to Fleming’s left hand rule, the centre finger gives the direction of current and middle finger points in the direction of magnetic field then the thumb points towards the direction of the force or motion of the conductor.
6. Name the lens that always produces erect, diminished and virtual image.
Ans:
A concave lens always produces erect, diminished and virtual image.
III. Answer the following questions. 2 x 2 = 4
7. Draw the diagram of the electric circuit used to study Ohm’s law and label voltmeter.
Ans:
8. ‘Bio-mass is a renewable source of energy’. Justify this statement with suitable reasons.
Ans:
Biomass is considered a renewable energy source because its inherent energy comes from the sun and because it can regrow in a relatively short time. Trees take in carbon dioxide from the atmosphere and convert it into biomass and when they die, it is released back into the atmosphere.
IV. Answer the following questions. 3 x 3 = 9
9. Draw the ray diagram to show the formation of image by a convex lens when the object is placed beyond 2F1 . Mention the position and nature of the image with help of the diagram. (F1 : Principal focus of the convex lens)
Ans:
10. What is electric current? Mention the use of battery in an electric circuit. Write the factors on which the resistance of a conductor depends.
Ans:
Electric Current is the rate of flow of electrons in a conductor.
The role of a battery (or cell) in an electric circuit is to supply energy to the circuit by doing work upon the charge to move it from the low energy terminal to the high energy terminal.
The resistance of the conductor depends on the following factors:
- The temperature of the conductor.
- The cross-sectional area of the conductor.
- Length of the conductor.
- Nature of the material of the conductor.
11. An electric lamp whose resistance is 20 Ω and a conductor of 4 Ω resistance are connected in series to a 6V battery. Find the current through the circuit and the potential difference across the electrical lamp and conductor.
Ans:
The resistance of the electric lamp R1 = 20 Ω.
The resistance of the conductor connected in series R2 = 4 Ω.
The total resistance in the circuit
R = R1 + R2
R = 20 Ω + 4 Ω = 24 Ω
the total potential difference across the two terminals of the battery V = 6 V.
By Ohm's law, the current through the circuit is given by
I = V/R
= 6 V/24
= 0.25 A
On applying Ohm's law to the electric lamp and resistor separately, we get potential difference across the electric lamp
V1 = 20 Ω × 0.25 A = 5 V
and that across the conductor
V2 = 4 Ω × 0.25 A = 1 V
OR
A copper wire has diameter 0.5 mm and resistivity of 1.6 x 10−8 Ω m. What should be the lenght of this wire to make its resistance 10 Ω.
Ans:
Area of cross-section of the wire, A =π (d/2) 2
Diameter= 0.5 mm = 0.0005 m
Resistance, R = 10 Ω
We know that
∴ length of the wire = 122.72m
V. Answer the following question. 1 x 4 = 4
12. State the laws of refraction of light. Different media have different refractive index. Why? ‘The refractive index of glass is 1.5’. What is the meaning of this statement?
Ans:
The incident ray refracted ray, and the normal to the interface of two media at the point of
incidence all lie on the same plane.
The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a
constant. This is also known as Snell's law of refraction.
Light propagates with different speeds in different media. The value of the refractive index for a given pair of media depends upon the speed of light in the two media.
Refractive index of glass is 1.5 . This means that the speed of light in glass is 1.5 times slower than the speed of light in vacuum.
OR
A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Find the magnification produced by the lens. With the help of this mention the nature of the image.
Ans:
f = -15 cm
v = -10 cm
Lens formula: 1/v – 1/u =1/f
1/-10 – 1/u = 1/-15
1/u = - (1/10) + 1/15
1/u = -2/60
u = -30 cm
Object is at 30 cm from the concave lens (on left side).
The nature of the image virtual, erect and diminished.
VI. Answer the following question. 1 x 5 = 5
13. Explain Faraday’s experiment of magnet and coil. What factors can be observed when the magnet is replaced by a coil carrying current? What are the conclusions that can be drawn by you from these experiments? State electromagnetic induction with the help of this experiment.
Ans:
Experiment 1: In this experiment, Faraday connected a coil to a galvanometer, As the bar magnet is shifted towards the coil, the pointer in the galvanometer gets deflected, thus indicating the presence of current in the coil. This shows that only the relative motion between the magnet and the coil are responsible for the generation of current in the coil.
Experiment 2: In the second experiment, Faraday replaced the bar magnet by a second current-carrying coil that was connected to a battery. As we move the second coil towards the primary coil, the pointer in the galvanometer undergoes deflection; all these results show that the system in the second case is analogous to the system in the first experiment.
Experiment 3:
He placed two stationary coils and connected one of them to the galvanometer and the other to a battery, through a push-button. As the button was pressed, the galvanometer in the other coil showed a deflection, indicating the presence of current in that coil. This proved that the relative motion between the coils was not really necessary for the current in the primary to be generated.
Conclusion: An emf is induced in the circuit changes with the amount of magnetic flux (number of magnetic lines per unit area) changes and magnitude of the induced emf in the circuit is equal to the time rate of change of magnetic flux through the circuit.
Electromagnetic Induction or Induction is a process in which a conductor is put in a particular position and magnetic field keeps varying or magnetic field is stationary and a conductor is moving. This produces a Voltage or EMF (Electromotive Force) across the electrical conductor.
PART: B CHEMISTRY
VII. Four alternatives are given for each of the following questions/incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 2 x 1 = 2
A. Methanal B. Methanone C. Ethanal D. Methanoic acid
Ans: A. Methanal
15. Observe the following stages of extraction of a metal from its ore. Sulphide ore → …………. → Reduction → Purification The process that has to be done in the empty space is
A. Electrolysis B. Calcination C. Roasting D. Oxidation
Ans: C. Roasting
VIII. Answer the following questions. 4 x 1 = 4
16. What is a strong acid?
Ans:
Acids that give high concentration of H+ ions on ionisation in aqueous solution are said to be strong acids
17. State modern periodic law.
Ans:
Moseley gave the Modern Periodic Law which states that: Physical and chemical properties of the elements are the periodic function of their atomic numbers.
18. The metallic property of elements increases down the group in the modern periodic table. Why?
Ans:
Metallic character increases as you move down an element group in the periodic table. This is because electrons become easier to lose as the atomic radius increases, where there is less attraction between the nucleus and the valence electrons because of the increased distance between them.
19. What is substitution reaction?
Ans:
The reactions in which an atom or group of atoms in a molecule is replaced or substituted by different atoms or group of atoms are called substitution.
IX. Answer the following questions. 3 x 2 = 6
20. The compounds C2 H4 , C3 H6 , C4 H8 , C5 H10 are in homologous series. Why? Write the general name and general formula for these carbon compounds.
Ans:
They have common difference of CH2 among each compounds. They have similar chemical properties. They have same functional groups .
The general formula :- CnH2n
The common name is :- alkenes
21. The atomic number of an element is 20. In which period of the modern periodic table, could this element be placed? Why? How will you decide whether the element is a metal or a non-metal?
Ans:
· The no. of shells present are 4 n therefore it belongs to period 4.
· As the elements placed towards the right-side or present in the s-block are metals, therefore this element is a metal.
22. Why is a metal oxide called a basic oxide? Name the products obtained when copper oxide reacts with dilute hydrochloric acid.
Ans:
Metallic oxides are basic in nature because they react with dilute acids to form salt and water.
copper oxide reacts with dilute HCl, it produces cuprous chloride(salt) and water.
OR
The test tube ‘A’ contains distilled water, test tube ‘B’ contains acidic solution and test tube ‘C’ contains basic solution. How could these samples be identified using red litmus paper.
Ans:
The solution which turns red litmus to blue contains a basic solution. The solution from the test tube which turns blue litmus paper to red will be the acidic solution and solution of the test tube which do not change either red or blue litmus paper contain water.
X. Answer the following questions. 3 x 3 = 9
23. Draw the diagram of the arrangement of the apparatus showing the reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning. Label the following parts :
(i) Zinc granules (ii) Delivery tube
Ans:
24. Explain the properties of carbon due to which it forms large number of compounds.
Ans:
(i) Catenation: The self linking property of an element mainly carbon atom through covalent bonds to form long straight, branched and rings of different sizes are called Catenation.
This property is due to
· The small size of the carbon atom.
· The great strength of the carbon-carbon bond.
(ii) Tetravalent Nature: Carbon has valency of four. It is capable of bonding with four other atoms of carbon or some other heteroatoms with single covalent bond as well as double or triple bond.
OR
Explain the cleaning action of soaps.
Ans:
Most of the dirt is oily in nature and oil does not dissolve in water. The molecule of soap constitutes sodium or potassium salts of long-chain carboxylic acids. In the case of soaps, the carbon chain dissolves in oil and the ionic end dissolves in water. Thus, the soap molecules form structures called micelles. In micelles, one end is towards the oil droplet and the other end which is the ionic faces outside. Therefore, it forms an emulsion in water and helps in dissolving the dirt when we wash our clothes.
25. Draw the diagram of the apparatus used in the electrolytic refining of copper. Label the following parts.
(i) Cathode (ii) Anode mud
Ans:
XI. Answer the following question. 1 x 4 = 4
26. a) Explain the formation of the ionic compound magnesium chloride with the help of electron dot structure.
Ans:
· During the formation of the ionic bond, a single magnesium atom loses two electrons. On the other hand, two chlorine atoms gain one electron each.
· Hence, magnesium atom becomes cation (positively charged ion) and each chlorine atoms become anions (negatively charged ion).
b) Write the balanced chemical equation for the reaction of aluminium metal with steam.
Ans:
2Al+3H2O→Al2O3+3H2
When steam is passed over aluminium , aluminium reacts with steam to form aluminium oxide and hydrogen gas.
PART: C BIOLOGY
XII. Four alternatives are given for each of the following questions/incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 2 x 1 = 2
27. The materials that change slowly their form and nature are
A. Used tea leaves B. Peels of vegetables
C. Waste papers D. Plants fibers
Ans: C. Waste papers
28. The pattern of response in the roots of plants is
A. Directional and negatively phototropic
B. Positively phototropic and negatively geotropic
C. Non-directional and positively geotropic
D. Growth dependent and positively hydrotropic
Ans: C. Non-directional and positively geotropic
XIII. Answer the following questions. 2 x 1 = 2
29. Mention the reason for the depletion of ozone layer.
Ans:
Ozone layer depletion is caused due to the release of chemical compounds containing gaseous bromine or chlorine from industries or other human activities.”
30. Name any two ancient systems that were practiced to harvest rain water.
Ans:
khadin, ponds, kuls, nadis….
XIV. Answer the following questions. 3 x 2 = 6
31. How is oxygen rich blood from the lungs supplied to all the cells in the human body?
Ans:
The right ventricle pumps the blood from the right atrium into the lungs to pick up oxygen and remove carbon dioxide. The left atrium receives blood from the lungs. This blood is rich in oxygen. The left ventricle pumps the blood from the left atrium out to the body, supplying all organs with oxygen-rich blood.
OR
How are the products of photosynthesis from the leaves get transported to all other parts of the plant?
Ans:
The food which is prepared by the process of photosynthesis in the leaves of a plant has to be transported to other parts like stem, roots, branches etc. Therefore this food is transported to other parts of the plant through a kind of tubes called phloem. Oxygen, a by-product of photosynthesis, and water vapor exit the leaf.
32. The people who live in and around the forest are said to be the stakeholders of the forest. Why? Explain.
Ans:
Local people around Forest are referred to as ''stkeholder''because Locals are depend on forest produce. Everyone uses forest resources in one form or the other. The stakeholders of forest resources include:
- People who live around the forest areas and depend upon the forest resources for sustenance.
- The Government Forest Department, which owns the forest land
- The industrialists who use forest products for various industrial purposes.
- The enthusiasts for the conservation of wildlife and natur
33. Draw the diagram showing the germination of pollen on stigma and label `female germ cell’.
Ans:
XV. Answer the following questions. 3 x 3 = 9
34. How do genes control the expression of ‘tall’ or ‘short’ traits in plants?
Ans:
Genes are the section of DNA that carry the chromosome and determine the characteristics of an organism.
Suppose, a plant species has a gene for tallness will give instructions to the plant cells to generate many plant-growth hormones due to which the plant will grow tall. On the other hand, if the plant has the gene for shortness then less plant-growth hormones will be produced, due to which the plant will not grow much and remain a dwarf plant.
Or
‘Acquired traits of an individual organism during its life time cannot direct the evolution’. Explain this statement with an illustration.
Ans:
Acquired traits are due to changes in the lifestyle, injury, loss of body parts, disuse of some body parts. These are the traits which occur in the somatic cells.These changes occur in the non-reproductive tissues, these cannot be passed into the DNA of the germ cells. hence acquired characters are not inherited.
35. In female reproductive system,
(i) How does an egg from the ovary reach uterus and develops into foetus?
Ans:
A pregnancy starts with fertilization, when a woman's egg joins with a man's sperm. Fertilization usually takes place in a fallopian tube that links an ovary to the uterus. If the fertilized egg successfully travels down the fallopian tube and implants in the uterus, an embryo starts growing.
(ii) What are the changes that occur in the uterus for the development of the foetus?
Ans:
During pregnancy, the lining of your uterus thickens and its blood vessels enlarge to provide nourishment to the fetus. As pregnancy progresses, your uterus expands to make room for the fetus. By the time your baby is born, your uterus will have expanded to many times its normal size.
Or
In sexual reproduction,
(i) How does the re-establishment of DNA amount occur in the new generation?
Ans:
When the gametes fuse during fertilization, the resulting new generation organism gets one pair of chromosome (Haploid) from each parent and thus the chromosome becomes diploid. Thus, the full number of chromosomes is re-established and the specific chromosome number of a species is maintained.
(ii) How is the amount of variations increase among the individuals of each of the population?
Ans:
Gene duplication, mutation, or other processes can produce new genes and alleles and increase genetic variation. New genetic variation can be created within generations in a population, so a population with rapid reproduction rates will probably have high genetic variation.
36. Draw the diagram showing the structure of nephron. Label the following parts. (i) Bowman’s capsule (ii) Collecting duct
Ans:
XVI. Answer the following questions. 2 x 4 = 8
37. a) How do the ‘homologous characteristics’ in different organisms help to identify the evolutionary relationships?
Ans:
organisms that share similar physical features and genomes tend to be more closely related than those that do not. Such features that overlap both morphologically (in form) and genetically are referred to as homologous structures; they stem from developmental similarities that are based on evolution.
b) How does Mendel’s ‘monohybrid cross’ experiment clarify that, `the traits of an organism independently inherit to the progenies?
Ans:
Genes located on different chromosomes will be inherited independently of each other. Mendel observed that, when peas with more than one trait were crossed, the progeny did not always match the parents. This is because different traits are inherited independently – this is the principle of independent assortmen
38. a) Name the mineral required for the production of thyroxine hormone. What is the use of this hormone to our body?
Ans:
· The thyroid gland uses iodine from food to make thyroid hormones
· Controls general metabolism and growth in the body.
b) What are involuntary actions? Name the parts of the human brain that control voluntary and involuntary actions.
Ans:
· Involuntary action is the set of muscle movement which do not require thinking. But it is controlled by brain for example beating of heart beat.
· The part of the brain that controls involuntary functions is medulla oblongata. The part of the brain that controls voluntary actions is cerebrum.
KREIS - SSLC SCIENCE MODEL QUESTION PAPER – 1
Sub: Science Sub. Code: 83E Time: 3.15 Hour Max Marks: 80
PART A: PHYSICS
I. Four alternatives are given for each of the following questions. Choose the correct alternative and write the complete answer along with its letter of alphabet. 4 x 1 = 4
1. The phenomenon of electromagnetic induction is
(a) the process of charging a body.
(b) the process of generating magnetic field due to a current passing through a coil.
(c) producing induced current in a coil due to relative motion between a magnet and the coil.
(d) the process of rotating a coil of an electric motor.
Ans: (c) producing induced current in a coil due to relative motion between a magnet and the coil.
2. Which of the following is not an example of a bio-mass energy source?
(a) wood (b) gobar-gas (c) nuclear energy (d) coal
Ans: (c) nuclear energy
3. The equation form of Joule’s law of heating is
a) V = IR b) H=I2RT c) H = RT d) I = HT
Ans: b) H=I2RT
4. The resistance of a wire of length “l” is “2R”. If the length of the wire is increased to “2l” then the resistance of the wire is
a) R/2 b) 4R c) 2/R d) R
Ans: b) 4R
II. Answer the following questions: 2 x 1 = 2
5. What is meant by emergent ray?
Ans:
Emergent Ray is the ray that comes out of a refracting medium.
6. When is the force experienced by a current–carrying conductor placed in a magnetic field largest?
Ans:
The force experienced by a current-carrying conductor is the maximum when the direction of current is perpendicular to the magnetic field's direction.
III. Answer the following questions: 2 x 2 = 4
7. Draw the diagram of the electric circuit which has resistors in series.
Ans:
8. State any two limitations associated with a wind mills?
Ans:
- It is Dependent on the Availability of Wind.
- Wind Turbines Kill Birds.
- The Energy that is Produced Can't Be Stored in Large Scale.
- the voltage remains constant in the parallel connection.
- We can use one appliance without using other appliances.
- The potential difference across each appliance is equal to the supplied voltage.
- Other components will function even if one component breaks down, each has its own independent circuit.
(i) Four components should be labelled.
(ii) All of them should be in parallel and there should be a fuse for safety.
(iii) Live and earth wires should be there.
The hydrocarbon part of the soap molecule links itself to the oily (dirt) drop and ionic end orients itself towards water and forms a spherical structure called micelles. The soap micelles helps in dissolving the dirt in water and wash our clothes.
- Magnesium chloride (MgCl₂) is formed by the ionic bond formed between magnesium and chlorine atoms.
- The electronic configuration of Mg is 2,8,2. Hence, magnesium needs to loose 2 electrons to become stable. Electronic configuration of chlorine is 2,8,7. Hence, chlorine needs to gain 1 electron to become stable.
- Therefore, during the formation of the ionic bond, a single magnesium atom loses two electrons. On the other hand, two chlorine atoms gain one electron each.
The UV radiations split apart some molecular oxygen (O2) into free oxygen (O) atoms which then combine with the molecular oxygen (O2) to form ozone (O3).
O2 -->O + O
O + O2 --> O3 (ozone).
- Plants produce two gaseous waste products i.e. oxygen during photosynthesis and carbon dioxide during respiration. Excretion of gaseous waste in plants takes place through stomatal pores on leaves..
- Excess of water is also excreted from the plant body through the stomatal pores and from the surfaces of fruits and stems.
- The gums, oils, latex, resins, etc. are some waste products stored in plant parts like barks, stems, leaves, etc. Eventually, plants shed off these parts.
- regulates water and soluble substances in the blood by filtering the blood,
- reabsorbing what is needed, and excreting the rest as urine.
- filter out wastes and toxins, and return needed molecules to the blood.
- It prevents soil erosion and floods.
- It helps to maintain the water cycle.
- It produces huge amounts of raw materials for the industries.
- It preserves different kinds of species and thus, maintains the species diversity.
2. Oral contraceptives: In this method, tablets or drugs are taken orally. These contain small doses of hormones that prevent the release of eggs and thus fertilization cannot occur.
3. Implants and surgical methods: Contraceptive devices such as the loop or Copper-T are placed in the uterus to prevent pregnancy. Some surgical methods includes the blocking of vas deferens to prevent the transfer of sperms known as vasectomy. Similarly, fallopian tubes of the female can be blocked so that the egg will not reach the uterus known as tubectomy.
(a) Formation of sperms by the process of spermatogenesis.
(b) Secretion of testosterone hormone.
Functions of ovary:
(a) Formation of ova by the process of oogenesis.
(b) Secretion of female hormones like estrogens, progesterone and relaxin.
- Wings of bats are skin folds stretched mainly between elongated fingers. But the wings of birds are a feathery covering all along the arm.
- Wing of a bat and wing of a bird can be considered as analogous organs because they have different basic structure, but have similar appearance and perform similar functions.
- Wings of bird and bat wings are analogous and wings of Birds and bats did not inherit from a common ancestor.
KREIS - SSLC SCIENCE MODEL QUESTION PAPER – 2
Sub: Science Sub. Code: 83E Time: 3.15 Hour Max Marks: 80
PART A: PHYSICS
I. Four alternatives are given for each of the following questions. Choose the correct alternative and write the complete answer along with its letter of alphabet. 3×1=3
1. Instrument used to detect electric current is _______
A) Galvanometer B) Fuse C) Ammeter D) Voltmeter
Ans: A) Galvanometer
2. At the time of short circuit, the current in the circuit
A) Reduce substantially B) Does not change
C) Increases heavily D) Vary continuously
Ans: C) Increases heavily
3. Which one of the following material cannot be used to make a lens?
A) Water B) Glass C) Plastic D) Clay
Ans: D) Clay
II. Answer the following questions: 2×1=2
4. What is Lens formula?
Ans:
The relation between distance of object, distance of image and focal length for a lens is called lens formula
u – Image distance, v – Object distance, f – Focal length5. What is the S.I. Unit of Potential difference? Name the device used to measure the potential difference.
Ans:
· The SI unit of potential difference is volt.
· A voltmeter is an instrument that is used to measure the potential difference across a conductor
III. Answer the following questions: 3×2=6
6. On what factors do the resistant of a conductor depends?
Ans:
· The type of material.
· The length of the conductor.
· The thickness of the conductor.
· The temperature of the conductor.
7. State Snell’s law of refraction with formula.
Ans:
Snell’s law State that “The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, for the light of a given colour and for the given pair of media”.
Sin i/sin r = constant
8. How much work is done in moving a charge of 2C across two points having potential difference 12Volt?
Ans:
q = 2C
V = 12V
W = V × q
W = 12V × 2C
W= 24 J.
IV. Answer the following questions: 3×3=9
9. Draw the Ray diagram, when object is placed in between F1 and 2F1 of a convex lens. And write nature, position and size of the image.
Ans:
Position of the image beyond 2f2
Nature real, inverted and enlorged
OR
Describe the size and nature of the image formed by the convex lens when object placed in the following positions, i. At infinity ii. At 2F1 iii. Between principle focus F and optical centre O.
Ans:
i. At infinity
· Size of the image is highly diminished
· Nature of the image is Real and Inverted
ii. At 2F1
· Size of the image is same size
· Nature of the image is Real and Inverted
iii. Between principle focus F1 and optical centre O.
· Size of the image is enlarged
· Nature of the image is virtual and erect
10. Draw diagram of simple electric motor.
Ans:
11. In a school there are 70 teachers. Most of them come by their personnel vehicle, where as there are many teachers who come from the same place. In this practice of coming will help nature? Justify it.
Ans:
· Most of them come by their personnel vehicle, they are promoting negligence towards environment, careless spending of resources but others are promoting environmental concern, sharing, helpfulness.
· many teachers who come from the same place, this way of commuting is nature friendly because they are saving fossil fuels, which are non-renewable sources of energy, by this practice and also reducing pollution.
· By switching off the lights and fans when not in use, turning off the engine of vehicles at red lights.
V. Answer the following questions: 2×4=8
12. Draw the circuit diagram for, Resistance in parallel and write advantages of parallel combination over series combination.
Ans:
· In parallel combination each appliance gets the full voltage.
· If one appliance is switched on/of others are not affected.
· The parallel circuit divide the current through the appliances. Each appliance gets proper current depending on its resistance.
· In a parallel combination it is very easy to connect or disconnect a new appliance without affecting the working of other appliances.
13. What is magnetic field? Mention the characteristics of magnetic field lines.
Ans:
The area around a magnet where a magnetic force is experienced is called the magnetic field.
- Magnetic field lines emerge from the north pole and merge at the south pole.
- As the distance between the poles increases, the density of magnetic lines decreases.
- The direction of field lines inside the magnet is from the South Pole to the North Pole.
- Magnetic lines do not intersect with each other.
PART B: CHEMISTRY
VI. Four alternatives are given for each of the following questions. Choose the correct alternative and write the complete answer along with its letter of alphabet. 3×1=3
14. The name of Carbon compound
A) Methanal B) Methanone C) Ethanoic acid D) Ethanal.
Ans: C) Ethanoic acid
15. Sulphide ore Reduction Purification. The process that has to be done in the empty space is,
A) Electrolysis B) Calcination C) Roasting D) Oxidation.
Ans: B) Calcination
16. The Non metal with electrical conductivity is,
A) Iodine B) Diamond C) Sulphur D) Graphite
Ans: D) Graphite
VII. Answer the following questions: 3×1=3
17. State Modern Periodic law.
Ans:
Modern Periodic Law which states that: Physical and chemical properties of the elements are the periodic function of their atomic numbers.
18. The metallic property of elements increase down the group in the modern periodic table. Why?
Ans: Metallic character increases down a group due to increase in atomic size. Thus, the outermost electrons are farther away from the nucleus and therefore can be lost easily. Hence, the electropositive character or metallic character increases
19. Write four methods to prevent corrosion.
Ans:
· By painting.
· BY applying grease or oil.
· By galvanisation:The process of depositing a thin layer of zinc metal on iron.
· By tin plating and chromium plating.
· By alloying it.
VIII. Answer the following questions: 3×2=6
20. Why is metal oxide called a basic oxide? Name the products obtained when copper oxide reacts with dilute Hydrochloric acid.
Metallic oxides are basic in nature because they react with dilute acids to form salt and water. Copper(II) oxide dissolves in mineral acids such as hydrochloric acid, sulfuric acid or nitric acid to give the corresponding copper(II) salts.
CuO + 2 HCl → CuCl2 + H2O.
OR
Test tube A contains distilled water, test tube B contains acidic solutions and test tube C contains basic solution. How these samples could be identified using red litmus paper?
· The solution which turns red litmus paper to blue contains a basic solution.
· Divide the obtained blue litmus paper into two parts.
· The solution from the test tube which turns blue litmus paper to red will be the acidic solution.
· Solution of the test tube which do not change either red or blue litmus paper contain water.
21. Draw a neat diagram showing Electrolytic refining of Copper and label the following parts: i. Cathode ii. Anode mud.
Ans:
22. Write Molecular and Molecular and structural formula for i. Benzene. ii. Butanol.
Ans:
Molecular formula of Benzene is C6H6 Molecular formula of Butanol is C4H9OH
Structural formula of Benzene is Structural formula of Butanol is
IX. Answer the following questions: 3×3=9
23. Draw the diagram of arrangement of apparatus showing the reaction of zinc granules with dilute sulphuric acid and testing Hydrogen gas by burning and label the following parts i. Zinc granules. ii. Delivery tube.
Ans:
24. Write the differences between saturated carbon compounds and unsaturated carbon compounds. Carbon forms covalent bonds with other atoms but not ionic bonds. Why?
Ans:
Saturated hydrocarbons
- Saturated hydrocarbons containing only single covalent bonds. These are also known as alkanes.
- These compounds are less reactive.
- Saturated hydrocarbons burns with blue flame
Unsaturated hydrocarbons
- Unsaturated hydrocarbons are the straight chain compounds containing double or triple covalent bonds are known as alkenes and alkynes.
- These compounds are more reactive.
- Unsaturated hydrocarbons burns with sooty flame.
OR
Explain the mechanism of cleaning action of Soap.
Ans:
Soaps and detergents contain two parts. A long hydrocarbon part which is hydrophobic (water repelling) in nature and a short ionic part which is hydrophillic (water attracting) in nature.
The hydrocarbon part of the soap molecule links itself to the oily (dirt) drop and ionic end orients itself towards water and forms a spherical structure called micelles. The soap micelles helps in dissolving the dirt in water and wash our clothes.
25. Give reasons for the following;
i. Ionic compounds in solid state do not conduct electricity where as molten state are good conductor of electricity.
ii. Silver articles when exposed to air gradually it turn blakish.
iii. Chemical reactions does not takes place when copper is added to iron sulphate solution.
Ans:
I. i. in a solid state, the ions cannot move and thus there is no flow of charge but in molten state, the anions and cations are free to move therefore it conduct electricity.
II. ii. Silver article when exposed to air gradually turn blackish because silver metal react with sulphur present in atmosphere and forms a layer of silver sulphide which is of black in colour.
iii. Copper less reactive than iron. It is placed at the bottom of the reactivity series, below iron. Therefore, copper cannot displace iron from iron sulphate solution.
X. Answer the following question: 1×4=4
26. Explain the properties of Carbon compounds.
Ans:
Chemical Properties of Carbon Compounds: The important chemical properties are as follows:
Combustion: Carbon burns in air or oxygen to give carbon dioxide and heat and light.
C(s) + O2(g) → CO2(g) + Heat and light
Oxidation reaction: Carbon and its compounds get easily oxidized when subjected to combustion. For example alcohol on oxidationis converted to carboxylic acid.
Addition Reaction: Addition of dihydrogen with unsaturated hydrocarbon in the presence of catalysts such as nickel or platinum or palladium are known as Hydrogenation (addition) reaction.
Substitution Reaction: Replacement of one or more hydrogen atom of an organic molecule by another atom or group of the atom is known as Substitution Reaction.
PART C: BIOLOGY
XI. Four alternatives are given for each of the following questions. Choose the correct alternative and write the complete answer along with its letter of alphabet. 2×1=2
27. the part of neuron that receive information is,
A) Axon B) Synapse C) Dendrites D) Cell body.
Ans: C) Dendrites
28. Cause for Ozone depletion is,
A) Chlorofluoro carbon B) Oxygen C) Hydrogen D) Nitrogen.
Ans: A) Chlorofluoro carbon
XII. Answer the following questions: 3×1=3
29. What are Nephrons?
Ans:
Nephron is the structural and functional unit of Kidney.
30. Who determines the sex in a child?
Ans:
A child's gender (male or female) is determined by the chromosome that the male parent contributes.
31. Mention the hormone responsible for diabetes.
Ans:
the hormone responsible for diabetes is insulin
XIII. Answer the following questions: 2×2=4
32. Mention disadvantages of constructions of Dams.
Ans:
- Environmental problem - deforestation leading to loss of biodiversity
- building a dam is very expensive
- Social problem - nearby towns and villages becomes homeless, Displacement of people during construction.
- There are chances of flooding, have to be relocated. They lose their businesses and farms
33. Write the differences between arteries and veins.
Ans:
Arteries
· Involved in carrying oxygenated blood except for pulmonary arteries.
· Valves are absent
veins.
· Involved in carrying deoxygenated blood except for pulmonary veins
· Valves are present
OR
What is double circulation?
Ans:
In the human heart, blood passes through the heart twice in one cardiac cycle. This type of circulation is called double circulation. One complete heartbeat in which all the chambers of the heart contract and relax once is called cardiac cycle. Double circulation ensures complete segregation of oxygenated and deoxygenated blood which is necessary for optimum energy production in warm-blooded animals.
XIV. Answer the following questions: 3×3=9
34. Explain the significant function of each structure in human male reproductive system.
Ans:
- Scrotum. The bag of skin that holds and helps to protect the testicles.
- The testicles make sperm and, the temperature of the testicles needs to be cooler than the inside of the body.
- The prostate gland is to produce the fluid that nourishes and transports sperm (seminal fluid).
- The vas deferens transports mature sperm to the urethra in preparation for ejaculation.
- The urethra thus forms a common passage for both the sperms and urine.
OR
Explain the structure and important role of placenta during pregnancy period of women.
Ans:
- The placenta is defined a disc shaped organ that develops during pregnancy in mammals.
- It attaches the fetus to the uterus of the mother during pregnancy.
- The placenta provides oxygen and nutrients to the growing fetus in the uterus of the mother.
- The waste materials from the fetus are excreted through the placenta.
35. Draw the diagram showing the structure of Nephrons and label the following parts; i. Bowman’s capsules. ii. Collecting duct.
Ans:
36. What is monohybrid cross? With help of checker board, write the monohybrid ratio of F2 generation between tall and dwarf pea plants.
Ans:
Monohybrid cross is a cross between parents differing in only one trait or in which only one trait is being considered.
Phenotypic ratio = 3: 1 (3 tall and 1 dwarf)
OR
What are homologous and analogous organs? Give examples for both.
Ans:
Analogous organs : Those organs which have different basic structure (or different basic design) but have similar appearance and perform similar functions are called analogous organs.
For example, The wings of an insect and a bird are analogous organs.
Homologous organs : Those organs which have the same basic structure (or same basic design) but different functions are called homologous organs.
For example, the wing of a bat, flipper of a seal, front leg of a horse and arm of a man are homologous organs.
XV. Answer the following question: 1×4=4
37. Draw a neat diagram of Human brain and label the following parts
i. Pons. ii. Cerebrum.
Ans:
XVI. Answer the following question: 1×5=5
38. a) Name the mineral required for production of thyroxin hormone.
What is the use of this hormone to our body?
What happens when the deficiency of this hormone occurs?
b) What are involuntary actions? Name the parts of human brain that control voluntary and involuntary actions?
Ans:
a)
- The mineral element required for the synthesis of thyroid hormones is iodine.
- Thyroid hormones play vital roles in regulating the body's metabolic rate, controlling heart, muscle and digestive function, brain development and bone maintenance.
- Deficiency is the leading cause for Goiter.
b)
- Involuntary action is the set of muscle movement which do not require thinking. But it is controlled by brain for example beating of heart beat.
- The medulla controls the involuntary actions whereas forebrain is responsible for controlling the voluntary actions in the body.
KARNATAKA RESIDENTIAL EDUCATIONAL INSTITUTIONS SOCEITY,
BANGALURU
Model Question Paper – 3 2020-21
Sub: Science Sub. Code: 83E Time: 3.15 Hour Max Marks: 80
PART A: PHYSICS
1. The commercial unit of electric charges is :
a. joule b. watt c. ampere d. Kilo watt hour
Ans: d. Kilo watt hour
2. The concave lens produces a magnification of +3. The object is placed :
a. at the focus b. between the focus and pole
c. between the focus and center of curvature d. beyond the center of curvature
Ans: b. between the focus and pole
3. The pattern of the magnetic field produced by the straight current carrying wire is:
a. in the direction opposite to the wire b. in the direction parallel to the wire
c. concentric circles around the wire d. in the same direction of current
Ans: c. concentric circles around the wire
II. Answer the following questions. 2 x 1 = 2
4. if the magnification of an object of 3m is 5, find the height of the image.
Ans:
Height of object = h = 3 m
Height of image = h' = ?
Magnification = m = 5
we know that,
m = h'/h
5 = h'/3
h' = 15m
Height of image is 15 metres
5. A ray of light bends when it travels from one medium into another. Why?
Ans:
A ray of light bends while going from one medium to another because of the phenomena of refraction. When the ray of light travels from one medium to another as the velocity of the light ray will either increase or decrease depending on the optical density of the material.
III. Answer the following questions. 3 x 2 = 6
6. Draw the ray diagram to show the formation of image by a convex lens when the object is kept at 2F.
7. a. Name the material used for making the filament of a bulb.
Ans: Tungsten is used for making filament of an electric bulb
b. Name two gases which are usually filled to prolong the life of filament of bulb.
Ans: Electric bulbs are usually filled with chemically inactive gases like nitrogen and argon
8. List two differences between ‘voltmeter and ammeter’.
Ans:
Ammeter | Voltmeter |
It is used to measure current | It is used to measure voltage across two points |
It is denoted by a symbol A | It is denoted by a symbol V |
IV. Answer the following questions. 3 x 3 = 9
9. Draw the diagram of an electric motor and Label the following parts. (i) Split rings (ii) Carbon brushes
10. A Concave lens has focal length of 20cm. At what distance from the lens a 5cm tall object be placed so that it forms an image at 15cm from the lens? Also calculate the size of the image formed.
OR
An object 5cm in length is held 25cm away from a converging lens of focal length 10cm. find the position, size and nature of the image formed.
Given that
The height of object = 5cm
Position of object, u = – 25cm
The focal length of the lens, f = 10 cm
We need to find
The position of the image, v =?
We know that
1/v – 1/u = 1/f
Substituting the known values in the above equation we get,
1/v + 1/25 = 1/10
=> 1/v = 1/10 – 1/25
=> 1/v = (5 – 2)/50
Hence, 1/v = 3/50
So, v= 50/3 = 16.66 cm
Therefore, the distance of the image is 16.66 cm on the opposite side of the lens.
Now, we know that
Magnification = v/u
Hence, m = 16.66/-25 = -0.66
Also, we know that
m= height of image/height of the object
Or, -0.66 = height of image / 5 cm
Hence, height of image = -3.3 cm
The negative sign of the height of the image depicts that an inverted image is formed.
So, the position of image = At 16.66 cm on the opposite side of the lens
Size of image = – 3.3 cm at the opposite side of the lens
Nature of image – Real and inverted
11. a. Why is thermal power plants setup near coal or oil fields?
b. List any four characteristic of good sources of energy
Ans:
a. Thermal power plants required coal and oil, which they burn to generate the required power. Since transmission of electricity is more efficient than transporting coal or oil over the same distance, So thermal power plants are generally located near coal fields.
b.
- It should provide large amount of energy per unit mass .
- It should be easily accessible .
- It should provide energy for maximum period of time and it should be renewable.
- It should be sustainable and safe for surrounding individual.
V. Answer the following questions. 2 x 4 = 8
12. a. State the rule to determine the direction of a
(i) Magnetic field produced around straight conductor – carrying current.
(ii) Force experienced by a current carrying straight conductor placed in a magnetic field which is perpendicular to it.
(iii) Current induced in a circuit by changing magnetic flux due to motion of a conductor.
Ans:
b. Why is a fuse wire made of tin – lead alloy and not copper?
Ans:
A fuse wire is made of tin alloy because it has low melting point, so that it may melt easily, whereas a copper wire cannot be used as a fuse wire because it has a high melting point due to which it will not melt easily when a short circuit takes place.
OR
a. What precautions should be taken to avoid the over loading of domestic electric circuits?
b. How does a solenoid behave like a magnet? Can you determine north and south poles of a current carrying solenoid using a bar magnet? Explain.
Ans:
a)
· Should not connect too many appliances to a single socket.
· Too many appliances should not be used at the same time.
· Faulty appliances should not be connected to the circuit.
· The fuse should be connected to the circuit in series.
b)
13. a) List the factors on which the resistance of a conductor in the shape of a wire depends.
Ans:
- The cross-sectional area of the conductor.
- Length of the conductor.
b) Differentiate between electric energy and electric power (any two).
Ans:
Electrical energy defines the energy generated due to the movement of charge carriers in a conductor. While electrical power specifies the rate of consumption of electrical energy by a device. The SI unit of electrical energy is Joules. But electrical power is measured in Watts (or KWh).
PART B: CHEMISTRY
VI. Four alternatives are given for each of the following questions/incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 3 x 1 = 3
14. Silver article become block on prolonged exposure to air. This is due to the formation of :
a. Ag2CO3 b. Ag2O c. Ag2S d. AgNO3
Ans: c. Ag2S
15. Which of the following will undergo addition reaction?
a. C3H8 b. C5H12 c. CH4 d. C4H8
Ans: d. C4H8
16. In the Mendeleev’s periodic table gaps were left for the element to be discovered later. Which of the following element found a place in the periodic table later?
a. Germanium b. Silicon c. Nitrogen d. Argon
Ans: a. Germanium
VII. Answer the following questions. 3 x 1 = 3
17. What change will you observe, if you test soap with litmus paper (red or blue).
Ans:
When soap is dissolved in water, the solution is alkaline in nature due to the formation of alkali NaOH or KOH. The solution changes the colour of red litmus to blue.
18. Lithium, Sodium and potassium forms a Dobereiner’s triads. The atomic masses of lithium and potassium are 7 and 39 respectively. Predict the atomic mass of Sodium.
Ans:
19. Aluminum is a highly reactive metal, yet it is used to make utensils for cooking. Give reason.
Ans:
This is because aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide. This oxide layer is very stable and prevents further reaction of aluminium with oxygen.
VIII. Answer the following questions. 3 x 2 = 6 20. Write the Structural formula and IUPAC name of the following compounds. i) A carboxylic acid with five C- atoms ii) An alcohol having two C- atoms.
VIII. Answer the following questions. 3 x 2 = 6
20. Write the Structural formula and IUPAC name of the following compounds. i) A carboxylic acid with five C- atoms ii) An alcohol having two C- atoms.
Ans:
I. Structural formula of a carboxylic acid with five C- atoms
IUPAC Name: Pentanoic acid
I. Structural formula of an alcohol having two C- atoms.
IUPAC Name: ethanol
OR
Complete the following equation for ‘X’ and identify ‘Y’
Ans:
23. The position of three elements X , Y and Z in the periodic table is given below
Answer the following questions with suitable reason.
i) Out of ‘Y’ and ‘Z’ which element will be more metallic?
ii) Will atomic size of ‘Z’ be smaller or larger than that of ‘X’?
iii) Out of ‘Y’ and ‘Z’ which element will be more electro negativity?
Ans:
i) Out of ‘Y’ and ‘Z’, Z element will be more metallic
ii) atomic size of ‘Z’ be smaller than that of ‘X
iii) Out of ‘Y’ and ‘Z’, Y element will be more electro negativity
24. Explain the mechanism of cleaning action of soap.
Ans:
Soaps and detergents contain two parts. A long hydrocarbon part which is hydrophobic (water repelling) in nature and a short ionic part which is hydrophillic (water attracting) in nature. The hydrocarbon part of the soap molecule links itself to the oily (dirt) drop and ionic end orients itself towards water and forms a spherical structure called micelles. The soap micelles helps in dissolving the dirt in water and wash our clothes.
OR
Differentiate between the saturated and unsaturated hydrocarbons.
Ans:
Saturated hydrocarbons:
- Saturated hydrocarbons containing only single covalent bonds. These are also known as alkanes.
- These compounds are less reactive.
- Saturated hydrocarbons burns with blue flame
Unsaturated hydrocarbons:
- Unsaturated hydrocarbons are the straight chain compounds containing double or triple covalent bonds are known as alkenes and alkynes.
- These compounds are more reactive.
- Unsaturated hydrocarbons burn with sooty flame.
25. Draw the diagram to show the reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning. Label the following parts a) Zinc granules b) Soap solution
X. Answer the following question. 1 x 4 = 4
26. a) Write the four properties of Ionic compounds.
Ans:
- They have high melting points and high boiling points.
- They're hard and brittle.
- They conduct electricity when they are dissolved in water.
- They're good insulators.
b) What is thermite reaction? Write its balanced chemical question.
Ans:
The thermite reaction is an exothermic reaction between the metal and metal oxide. For example the reaction between the aluminium with the metal oxides, where aluminium acts as a reducing agent. The aluminium reduces the metal oxide most probably an iron (lll) oxide to produce ferrous and aluminium oxide. During the reaction, large amount of energy is released.
Fe2O3 + 2Al → 2Fe + Al2O3 + heat
PART C: BIOLOGY
XI. Four alternatives are given for each of the following questions/ incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 2X1=2
27. Government launched the “Ganga action plan” (GAP) in 1985. The main purpose of this project was to
a) utilize the river water for irrigation purpose
b) improve the quality of water
c) promote the quality of aquatic life like Fish
d) build new dams over the Ganga river
Ans: b) improve the quality of water
28. Which of the following radiation is responsible for the conversion of atmospheric oxygen to ozone?
a) gamma radiation b) cosmic radiation
c) infrared radiation d) ultra violate radiation
Ans: d) ultra violate radiation
XII. Answer the following questions. 3x1=3
29. Why is ozone layer getting depleted at the higher level of the atmosphere?
Ans:
Ozone layer is getting depleted at the higher levels of the atmosphere due to effect of chlorofluorocarbons CFCs which are used as refrigerants and in fire extinguishers.
30. Suggest two consequences due to the loss of biodiversity.
Ans:
(a) decline in plant production,
(b) lowered resistance to environmental perturbations such as drought
31. Give an example where sex is determined by environmental factor.
Ans:
Incubation temperature determines sex in some of the animals like crocodiles, where the high temperature incubates maleness and low temperature produces femaleness.
XIII. Answer the following questions. 2x2=4
32. Draw the diagram showing the germination of pollen on stigma and label ‘Pollen tube’.
33. Write the flow chart showing ‘Reflex arc’
OR
Write the name and functions of two parts of ‘human hind brain’.
Ans:
Two main parts of hind-brain are — Medulla and Cerebellum.
Their functions are:
Medulla : Involuntary actions such as blood pressure salivation and vomiting.
Cerebellum : It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.
XIV. Answer the following questions. 3x3=9
34. How is sex of a child determined in human beings?
Ans:
The males have XY sex chromosomes. They produce two types of gametes having X and Y chromosome. The females have XX chromosome. They produce only one type of gamete having X chromosome. If sperm is having X chromosome, then the child will be a girl. If sperm is having Y chromosome, then the child will be a boy.
OR
What is speciation? List four factors that could be lead to speciation.
Ans:
Speciation is an process of forming a new species from other existing species.
Factors that lead to speciation:
· Geographical isolation.
· Genetic drift.
· Natural selection.
· Reproductive isolation.
35. What is placenta? Describe its structure, state its two function in pregnant human female.
Ans:
Placenta is a special tissue connection between embryo and uterine wall. It acts as an endocrine gland.
Placenta is a disc like structure that forms a connection between the embryo and the uterine wall. It possesses villi that increase the surface area for absorption of nutrients.
Role of placenta:
- Facilitates passage of nutrition and oxygen to embryo from mother through blood.
- Waste substances produced by embryo are removed through placenta into mother’s blood.
OR
Why does menstruation occurs?
Ans:
The ovary releases one egg every month and the uterus prepares for the implantation of the zygote by thickening its walls. The thick wall is not necessary if the egg is not implanted. Thus , the uterine lining slowly breaks down and comes out through the vagina as blood and mucus. This cycle takes place roughly every month and is known as menstruation and lasts for about two to eight days.
36. A blue color flower plant denoted by ‘BB’ is cross bred with that of white colour flower plant denoted by ‘bb’
a) State the colour of flower you would expect in their ‘F1’generation plant
b) What must be the percentage of white flower plants in ‘F2’ if flowers of ‘F1’ plants are self pollinated?
c) Write the expected ratio of the genotypes ‘BB’ and ‘Bb’ in the F2 progeny.
Ans:
a) the colour of flower you would expect in their ‘F1’generation plant is blue
b) be the percentage of white flower plants in ‘F2’ if flowers of ‘F1’ plants are self pollinated is 25%
c) the expected ratio of the genotypes ‘BB’ and ‘Bb’ in the F2 progeny is 1:2
XV. Answer the following questions. 1x4=4
37. Draw the diagram showing the longitudinal section of the human brain. Label the following parts. a) cerebrum b) Medulla
XVI. Answer the following questions. 1x5=5
38) a) Write the characteristics and functions of three types blood vessels.
Arteries:
Arteries are the main blood vessels that carry and transport oxygenated blood or oxygen-rich blood from the heart to other parts of the body. They are the strongest blood vessels with thicker walls and are muscular in nature.
Veins:
Veins are thin, tube-like elastic blood vessels and carry impure or deoxygenated blood from all parts of the body to heart.
Capillaries:
Short and tiny blood vessels and bring about the exchange of substances between blood and tissues.
b) What is translocation? How does it take place in plants?
Ans:
Transport of soluble product of photosynthesis or food from leaves to other parts of plants is called translocation.
For translocation, food molecules enter the part of the phloem called the sieve tubes where they can be transported upwards or downwards to all the parts of the plant including roots.
Translocation is achieved by utilising energy from the ATP that provides osmotic pressure required for upward and downward movement of food.
KREIS - SSLC SCIENCE MODEL QUESTION PAPER – 4
Sub: Science Sub. Code: 83E Time: 3.15 Hour Max Marks: 80
PART A: PHYSICS
I. Four alternatives are given for each of the following questions/incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 3 x 1 = 3
(1) What is the relationship between resistance and current
(a) They are directly related to each other
(b) They are inversely related to each other
(c) The resistance has greater magnitude than current
(d) The current has a greater magnitude than resistance
Ans: (b) They are inversely related to each other
(2) Appliances that have metal body are generally connected to the earthing wire what is the reason to earth these wires ?
(a) To prevent excess of current
(b) To prevent the leakage of current
(c) To prevent extra current to appliance
(d) So prevent high resistance to the appliance
Ans: b) To prevent the leakage of current
(3) I dioptre of power of a lens is equal
(a) 1 m-1 (b) m (c) 1m (d) 1m-2
Ans: (a) 1 m-1
II. Answer the following. 1X2=2m
(4) The power of lens is -20, what is focal length ?
Ans:
Power of a lens is -20D, negative sign indicates it is a Concave lens.
Focal length (in meters)=1/power of the lens,
Thus, focal length=1/20 = 0.05m = 5cm.
(5) The speed of light in air is 3X108 ms -1 where as that of the speed of light in water is 2.26 X 108 ms -1 what is the refractive index of water with respect to air ?
Ans:
Refractive index of water with respect to air = speed of light in water/speed of light in air
= 2.26 X 108 ms -1 / 3X108 ms -1
= 1.3
III. Answer the following. 2X3=6m
(6) Draw the ray diagram to show the formation of image by a convex lens when the object is kept in 2F
Ans:
(7) Study the following electric circuit and find
(a) The current flowing in the circuit and
(b) The potential difference across 10 Ω resistor
Ans:
R = R1 + R2 = 10 + 20 = 30Ω
V = 3 V
(i) From ohm's law V = IR
3 = I × 30 ⇒ I = 3 / 30 = 1 / 10 Ampere or 0.1 A
(ii) Potential difference across 10Ω resistor
V = IR
= 1 / 10 = 1 volt
(8) Find the current flowing through the following electric circuit
Ans:
Series combination of 1 Ω and 3 Ω resistance is in parallel combination with 6 Ω .Their equivalent resistance is
Now, 3.6 Ω 2.4 Ω and 3 Ω are in series, their equivalent resistance be
Rs = R1 + R2 + R3 = 3.6 + 2.4 + 3 = 9 Ω
Hence, the current flowing through the circuit is
IV. Answer the following. 3X3=9m
(9) Draw a neat labelled diagram of electric motor.
Ans:
(10) (a) The image of an object placed at60 cm in front of a lens is obtained on a screen at a distance of 120 cm from it. Find the focal length of the lens. What would be the height of the image if the object is 5cm high ?
Ans:
u=−60cm.
OR
(b) List the sign conventions that are followed in case of refraction of light through spherical lenses. Draw a diagram and apply these conventions in determining the nature and focal length of a magnified real image of an object placed 16 cm from the lens.
Ans:
Sign convention for the refraction of light is as follows.
- All the distances are measured from the optical centre of the lens.
- All the distances which are measured in the same direction of the incident light ray (left hand side of lens) will be taken as positive.
- All the distances which are measured against the direction of incident light (right hand side) are taken as negative.
- The perpendicular distances to principal axis in upward direction will be positive and those in downward direction will be taken as negative.
Figure below illustrates the conventions more clearly.
According to the question.
Magnification (m) = -3 (real image is always inverted).
Object distance (u) = -16cm.
By Magnification Formula;
Magnification, m = v/u
where,
v is the image distance,
u is the object distance
Therefore the focal length is 12 cm. Since the focal length is positive, therefore the lens is convex lens.
Figure below shows the ray diagram for the same.
(11) Biogas is an excellent fuel justify the statement by giving two reasons mention the main constituents of biogas
Ans:
(i) It burns without smoke and leave no residue therefore causes no atmospheric pollution. (ii)Its heating capacity is high, i.e. it has high calorific value.
Main constituents of bio gas: Methane, Carbon dioxide, Nitrogen, Hydrogen and Hydrogen sulphide
OR
State any three advantages of charcoal over wood.
Ans:
· Charcoal has a low ignition temperature or kindling point as compared to wood.
· Charcoal produces less smoke than wood.
· Charcoal has a higher calorific value than wood.
V. Answer the followings: 2X4=8m
(12) Explain the underlying principle and working of an electric generator.
Ans:
Principle : The electric generator is based on the principle of electromagnetic induction. When a coil is rotated with respect to a magnetic field, the number of magnetic field lines through the coil changes. Due to this a current is induced in the coil whose direction can be found by Fleming’s right hand rule.
Working : When the armature coil ABCD rotates in a magnetic field produced by the permanent magnets, it cuts through the magnetic lines of force.
Due to the rotation of armature coil, the associated magnetic field changes and an induced electromagnetic force is produced in it. The direction of this induced electromotive force or current can be determined by using Fleming’s right hand rule.
In first half cycle the current flows in one direction by brush B1 and in second it flows in opposite direction by brush B2. This process continues. So the current produced is alternating in nature.
Functions of Brushes : Brushes in contact with rings provide the current for external use.
OR
A coil of insulated copper wire is connected to a galvanometer what will happen if a bar magnet is 1) Pushed into the coil 2) Withdraw from inside the coil 3) Held stationary inside the coil
Ans:
(i) when magnet is pushed near a bar magnet then it induces current due to electromagnetic induction.
(ii) When the bar magnet is withdrawn from inside the coil of the insulated copper wire again the current is induced in the coil but this time it is in reverse direction.
(iii) When a bar magnet is held stationary inside the coil then no current is induced that’s why galvanometer will show no deflection.
(13) (a) Write two points of difference between electric energy and electric power (b) Out of 60w and 40w lamps, which one has higher electric resistance when in use. (c) What is the commercial unit of electric energy? Convert it into joules.
Ans:
a) Electrical energy defines the energy generated due to the movement of charge carriers in a conductor. While electrical power specifies the rate of consumption of electrical energy by a device. The SI unit of electrical energy is Joules. But electrical power is measured in Watts (or KWh).
b) Resistance and power are inversely proportional to each other. So, lamp powered 40 W has more resistance than a 60 W lamp.
c) Commercial unit of electric energy is kilowatt hour(kWh).
PART B: CHEMISTRY
VI. For Alternatives are given for each of the following questions/incomplete Sentences. Choose the correct alternatives and write the complete answer along its letter of alphabets. Choose the correct answer. 1X3=3m
(14) Most reactive metal among the following is
(a) Na (b) Mg (c) Zn (d) Cu
Ans: (a) Na
(15) In modern periodic table, as we move from left to right along the period the metallic nature of the element
(a) Increases (b) Does not change
(c) Decreases (d) first increases & then decreases
Ans: (c) Decreases
(16) The image represents a carbon compound Which functional group is present in the compound?
(a) alcohol (b) aldehyde (c) ketone (d) carboxylic acid.
Ans: (c) ketone
VII. Answer the following. 1X3=3m
(17) Why electric wires are made up of copper?
Ans:
Copper is a good conductor of electricity and it is not much expensive. This is the reason why the electric wires are made of copper
(18) Carbon from compound mainly by covalent bonding. Give reason for your answer.
Ans:
Carbon forms covalent bonds with other atoms but not ionic bonds because Losing or gaining 4 electrons is not possible due to energy considerations in carbon. Hence, it shares electrons to form covalent bonds.
(19) 18th group elements are called as noble gases why?
Ans:
These elements are non-reactive and are called noble gases as they have their outermost orbit complete. Due to stable electronic configuration they hardly react with other elements.
VIII. Answer the following. 3X2=6m
(20) Name the aldehyde having four carbon atoms and write its structure.
Ans:
OR
Explain the mechanism of cleaning action of soap.
Ans:
Soaps and detergents contain two parts. A long hydrocarbon part which is hydrophobic (water repelling) in nature and a short ionic part which is hydrophillic (water attracting) in nature. The hydrocarbon part of the soap molecule links itself to the oily (dirt) drop and ionic end orients itself towards water and forms a spherical structure called micelles. The soap micelles helps in dissolving the dirt in water and wash our clothes.
(21) Draw the diagram of reaction of Zinc granules with dil H2So4 and testing hydrogen gas by burning
Ans:
(22) Dry hydrogen chloride gas does not turn blue litmus where as hydrochloric acid why?
Ans:
Acidity is due to the ability of giving H+ ion. Dry hydrogen chloride does not give hydrogen ions and so it does not act as an acid and does not turn blue litmus red.
I X. Answer the following: 3X3 =9m
(23) Explain about the limitations of Newland’s law of octaves.
Ans:
· Law of Octaves only applicable upto calcium and after calcium every 8th did not possess properties similar to that of the first.
· later on , several new elements were discovered, whose properties did not fit into the law of octaves.
· Newlands'law of Octaves worked well with lighter elements only.
(24) Write the differences between soaps and detergents.
Ans:
SOAP | DETERGENT |
1. Sodium salt of Carboxylic acids | 1. Sodium salts of benzene sulphonic acids. |
2. Soaps are bio-degradable | 2. Some detergents are non- biodegradable |
3. Soaps do not lather in hard water | 3. Detergent lather well in hard water |
4. Weak cleansing action | 4. Have strong cleansing action |
OR
Why micelle does form when soap is added to water?
Ans:
Soap molecule has two ends. One end is hydrophilic and another end is hydrophobic. When soap is dissolved in water and clothes are put in the soapy solution, soap moleucles converge in a typical fashion to make a structure, called miceele. The hydrophobic ends of different molecules surroound a particle of grease and make the micelle, which is a spherical structure. In this, the hydrophilic end is outside the sphere and hydrophobic end is towards the centre of the sphere. This is why micelle formation takes place when soap is added to water.
(25) Draw the neat labelled diagram of electrolytic refining of copper.
Ans:
X. Answer the following 1X4=4m
(26) (a) What is corrosion ? Write the methods to prevent corrosion, which metals do not corrode easily ?
Ans:
Corrosion is the process in which metals are eaten up gradually by the action of air, moisture or a chemical in their surface.
· By painting.
· BY applying grease or oil.
· By tin plating and chromium plating.
· By alloying it.
Noble metals such as gold and platinum do not corrode easily.
(b) What is an amphoteric oxide? Write the two chemical properties of metals?
Ans:
Amphoteric oxides are the oxides that behave as both acidic and basic oxides. Amphoteric oxides have properties of acidic as well as basic oxides that neutralize both acids and bases.
· Metals are malleable and ductile.
· Metals are good conductors of heat and electricity.
PART C: BIOLOGY
XI. For Alternatives are given for each of the following questions/incomplete Sentences. Choose the correct alternatives and write the complete answer along its letter of alphabets. Choose the correct answer. 2X1=2m
(27) Which of these practices can be adopted to save the environment?
(a) Refuse the use of single - Use plastic bags
(b) Reduce the use of - paper bags
(c) Recycle single - use bags
(d) Reduce - waste food.
Ans: (d) Reduce - waste food.
(28) The correct sentences which respect to biodegradable substances.
(a) Remain insert in the environment for a long time
(b) Harm viruses organisms in the ecosystem
(c) Increase the density of harmful chemicals in difference topic levels
(d) undergo recycling neatly in the environment
Ans: (d) undergo recycling neatly in the environment
XII. Answer the following: 3X1=3m
(29) Mention the reason for depletion of Ozone layer
Ans:
The reason for depletion of Ozone layer is Chlorofluorocarbons or CFC. These are released by solvents, spray aerosols, refrigerators, air-conditioners, etc.
(30) Why do we use fossil fuels judiciously?
Ans:
We need to use fossil fuels judiciously because they are non-renewable resources. We need to conserve fossil fuels so we don't run out of them.
(31) Mention any two problems caused by the constructions of huge dams?
Ans:
· Economic problems : Construction of dams requires a huge amount of monetary investments
· Environmental problems : Construction of dams across rivers leads to deforestation, which results in the loss of biodiversity. This disturbs the natural ecosystem.
XIII. Answer the following: 2X2=4m
(32) How are involuntary actions and reflex actions differ from each other?
Ans:
Involuntary action is the set of muscle movement which do not require thinking. But it is controlled by brain for example beating of heart beat. While on the other hand, the reflex action is rapid and spontaneous action in response to any stimulus which doesn't involve brain.
OR
Name the different types of tropisms exhibited by the plants and write their meaning.
Ans:
The different types of tropisms are:
(i) Phototropism: The movement of plant parts in response to light is known as phototropism. The stimulus is light.
(ii) Geotropism: The movement of plant parts in response to gravity is known as geotropism. The stimulus is gravity.
(iii) Hydrotropism: The movement of plant parts in response to water is known as hydrotropism. The stimulus is water.
(iv) Chemotropism: The movement of plant parts in response to chemicals is known as chemotropism. The stimulus is chemicals.
(33) Draw the diagram showing the longitudinal section of typical flower and label the parts.
Ans:
XIV. Answer the following 3X3 =9m
(34) Will Geographical isolation be a major factor in the speciation of a self pollination plant species ? why of why not ?
Ans:
In a self-pollinating plant species, geographical isolation cannot be a major factor in speciation because no new trait can become a part of the genetic makeup in a self-pollination plant species. However, there are some chances of some environmental changes which might lead to some variations.
OR How is the sex of the child determined in human beings?
Ans:
The males have XY sex chromosomes. They produce two types of gametes having X and Y chromosome. The females have XX chromosome. They produce only one type of gamete having X chromosome. If sperm is having X chromosome, then the child will be a girl. If sperm is having Y chromosome, then the child will be a boy.
(35) What is the role of seminal vesicle and the prostate gland? What are the functions performed by the testis in human beings ?
Ans:
Seminal vesicles and prostate gland occur in male reproductive system. The seminal vesicles and prostate gland add their secretios to the vas deferens which carries sperms from the testes. The secretions of seminal vesicles and prostate gland provide nutrition to the sperms and also make their further transport easier.
Testis are components of both the reproductive system and the endocrine system. The functions of the testicles are producing sperm and producing male sex hormones testosterone
OR
What are the different methods of contraception? What are the functions of placenta? What are the changes seen in girl at the time of puberty?
Ans:
Barriers, IUDs (IntraUterine Devices), Oral contraceptives, Implants, Injectables, and surgical methods.
Transmission of nutrients and oxygen from mother to the fetus and the release of carbon dioxide. The waste materials from the fetus is excreted through the placenta.
The various changes which occur in girls at puberty are: Hair grow under armpits and pubic region. Mammary glands (or breasts) develop and enlarge. Fallopian tubes, uterus and vagina enlarge. Ovaries start to release eggs. Menstruation (montly periods) starts.
(36) (a) How are the areas of study of evolution and classification interlinked ?
(b) Differentiate between acquired traits and inherited traits.
Ans:
a)
Classification and evolution are highly interlinked fields of study because the classification of an organism is influenced by its evolution. An organism may have a different type of look based on its morphology and are classified into a different group as compared to the other organism.
b)
XV. Answer the following 1X4=4m
(37) Draw the diagram of showing in the longitudinal section of the human brain label the following parts (a) Pituitary gland (b) Cerebrum
Ans:
XVI Answer the following 1X5=5m
(38) (a) What are the components of the transport system in human beings what are functions of these components ?
(b) How are waste material excreted in plants ?
Ans:
a)
The main components of the transport system in human beings are the heart, blood, and blood vessels.
· Heart pumps oxygenated blood throughout the body. It receives deoxygenated blood from the various body parts and sends this impure blood to the lungs for oxygenation.
· Blood is a fluid connective tissue, it helps in the transport of oxygen, nutrients, CO2, and nitrogenous wastes.
· Blood vessels (arteries, veins, and capillaries) carry blood either away from the heart to various organs or from various organs back to the heart.
b)
- Plants produce two gaseous waste products i.e. oxygen during photosynthesis and carbon dioxide during respiration. Excretion of gaseous waste in plants takes place through stomatal pores on leaves..
- Excess of water is also excreted from the plant body through the stomatal pores and from the surfaces of fruits and stems.
- The gums, oils, latex, resins, etc. are some waste products stored in plant parts like barks, stems, leaves, etc. Eventually, plants shed off these parts.
KREIS - SSLC SCIENCE MODEL QUESTION PAPER – 5
Sub: Science Sub. Code: 83E Time: 3.15 Hour Max Marks: 80
PART A: PHYSICS
I. Four alternatives are given for each of the following questions. Choose the correct alternative and write the complete answer along with its letter of alphabet. 4x1=4
1. A rectangular coil of copper wire is rotated in a magnetic field. The direction of the induced current changes once in each:
a) two revolutions b) one revolution c) half revolution d) one-fourth revolution
Ans: c) half revolution
2. Which of the following is a non-renewable source of energy?
a) wood b) Fossil fuels c) sun d) wind
Ans: b) Fossil fuels
3. The work done in moving a charge of 2C across two points having a potential difference 12V is:
a) 24 J b) 6 J c) 14 J d) 10 J
Ans: a) 24 J
4. Electrical resistivity of a given metallic wire depends upon:
a) its length b) its thickness c) its shape d) nature of the material
Ans: d) nature of the material
5. Mention the advantage of A.C over D.C for long distance transmission.
Ans:
AC is less expensive and easy to generate than DC. The distance covered by AC is more than that of the DC. The power loss during transmission in AC is less when compared to the DC.
6. Define focal length.
Ans:
Focal length of a lens is the distance between centre of lens and focal point .
III. Answer the following questions: 2x2=4
7. What are the properties of a good source of energy?
Ans:
· It produces a lot of heat per unit mass.
· It is easily accessible.
· It is easy to store and transport.
· It produces less amount of smoke.
8. Draw the circuit diagram showing the combination of resistors R1, R2, R3 in parallel, including voltmeter, plug key and battery.
Ans:
IV. Answer the following questions: 3x3=9
9. Draw a ray diagram when the object is kept at 2F1 of the convex lens. With the help of the diagram mention the position and nature of the image formed.[ F1: principal focus of the lens]
Ans:
Position of image at 2F2, Nature of the image is real and inverted.
10. i) What is meant by electric current?
ii) How can we bring potential difference in an electrical circuit?
iii) Define the S.I. unit of potential difference.
Ans:
i) Electric current is rate of flow of electric charge or the amount of charge flowing through a particular area in unit time.
ii) In a conductor, electrons flow only when there is a difference in electric pressure at its ends. This is also called potential difference. In a circuit, this potential difference is created by a battery.
iii) S.I. unit of potential difference is volt
11. The current drawn by an electric heater coil is 2A from 220V source. Calculate its resistance. If it draws 1A current find the potential difference of the circuit.
Ans:
We know that
Resistance=voltage/current
Here, V=220 I=2A
R=220/2
R=110ohms
2nd case
voltage=current×resistance
i=1A R=110ohms
Therefore,
1×110=110volts
The potential difference of the circuit is 110volts
OR
An electric iron consumes energy at a rate of 840w when heating is at the maximum rate and 360w when the heating is at the minimum. The voltage is 220V what are the current and the resistance in each case.
Ans:
Given, Voltage of the mains supply, V = 220 V
Power is given by, P = VI
Case 1: When heating is at maximum rate,
Power, P = 840 W
Potential difference, V = 220 V
Current, I = P/V = 849W/220V = 3.82A
∴ Resistance of the electric iron, R = V/I=220V/3.82A=57.60Ω
Case 2: When heating is at the minimum rate,
Power, P = 360 W
Potential difference, V = 220 V
Current, I = P/V=360W/220V=1.64A
∴ Resistance of the electric iron,
R=V/I=220V/1.64A=134.15Ω
V. Answer the following questions: 1x4=4
12. Define power of lens. Power of a lens is +1.0D. What does it mean? Which type of lens it is?
Ans:
The power of a lens is defined as the reciprocal of its focal length.
1 dioptre of power of a lens is described as the unit of measurement of the optical power of a lens or curved mirror equivalent to the reciprocal of focal length (f). Power is P = 1/f in m. + 1.0 D = 1/f in m. ∴ f = 1.0 m.
The positive sign indicates that the focal length of the lens is positive which indicates the lens is a convex lens.
OR
The refractive index of A, B and C is 1.44, 1.54 and 1.36 respectively.
i) Which is optically denser medium?
ii) To which side the light bends when it travels from medium C to medium A
iii) To which side, the light bends when it travels from medium A to medium B
Ans:
i) B-1.55 is optically denser medium
ii) The light bends towards normal when it travels from medium C to medium A
iii) The light bends towards normal when it travels from medium A to medium B
VI. Answer the following questions: 1x5=5
13. a) Define the followings:
i) solenoid ii) commutator
b) What is electric motor? Explain the working of electric motor.
Ans:
A coil of many circular turns of. insulated copper wire wrapped closely in the shape of a cylinder is called solenoid.
A device that reverses the direction of flow of current through a circuit is called a commutator.
The principle of the electric motor is based on the fact that a current carrying conductor produces a magnetic field around it. A current carrying conductor placed perpendicular to magnetic field experiences a force.
The working of an electric motor is based on the fact that a current carrying conductor produces a magnetic field around it.
Once electricity flows through simple circuit, loop “moves”. The magnetic field of the magnets interferes with that produced due to electric current flowing in the conductor. Since the loop has become a magnet, one side of it will be attracted to the north pole of the magnet and the other to the south pole. This causes the loop to continuously rotate. This is the principle of working of electric motor.
PART B: CHEMISTRY
VII. Four alternatives are given for each of the following questions. Choose the correct alternative and write the complete answer along with its letter of alphabet. 2x1=2
14. An example for saturated hydrocarbon is:
a) C2H6 b) C3H4 c) C2H2 d) C2H4
Ans: a) C2H6
15. Which one of the following metals does not react with cold as well as hot water?
a) Na b) Ca c) Mg d) Fe
Ans: d) Fe
VIII. Answer the following questions: 4x1=4
16. Write the industrial applications of detergent?
17. The atomic number of element ‘X’ is 20. The element belongs to which period in periodic table?
Ans:
Its electronic configuration is 2,8,8,2. Hence it belongs to 4th period in periodic table. Since it occupies four shells..
18. Why should curd and sour substances not be kept in brass and copper vessels?
Ans:
Both the Curd and sour substances are acids. Acids react with metals to produce salt and hydrogen gas. So, if such substances are kept in a copper container, the acid will react and the container will be corroded. Thereby may spoil the food.
19. When we move down a group what happens to the electro negativity?
Ans:
Electronegativity is a measure of an atom's ability to attract shared electrons to itself. On the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you move down a group.
IX. Answer the following questions: 3x2=6
20. Define the term isomers and give an example.
Ans:
The organic compounds having the same molecular formula but different structures are known as isomers for ex : n-butane and iso-butane are isomers.
21. When few drops of orange juice is added to pure water, how does the pH value vary for water? If few drops of lemon juice is also added, will there be any more change in the pH value?
Ans:
When a drop of orange juice is added to the water, the acid releases H+ ions on dissociation. This lowers its pH value making it acidic in nature. If a drop of lemon juice is added to it, the concentration of citric acid will increase further resulting in lowering the pH from 7.
OR
Two solutions P and Q are tested with universal indicator. The solution P turns red, whereas solution Q turns orange. Which solution (i) is more acidic? (ii) has more pH?
Ans:
(i) The solution P is more acidic
(ii) The solution Q has more pH
22. The positions of the A, B, C, D elements in the modern periodic table are given in the table below. Look at the table and answer the following questions.
i) Which element is having maximum size of atomic radius? Why?
ii) Which element is having lowest metallic property? Why?
Ans:
i) Element C is having maximum seize of atomic radius because Atomic size decreases in moving from left to right along a period and Atomic size increases down the group.
ii) Element B is having lowest metallic property, because Metallic character increases down each Group of the Table. Metallic character decreases from left to right in each Period.
X. Answer the following questions: 3x3=9
23. Draw a diagram to show testing the conductivity of a salt solution and label the following parts. a) graphite rod b) salt solution under test
Ans:
24. What are the two ends of present in a soap molecule? Which of these ends are hydrophobic and hydrophilic? Why soaps cannot clean in hard water?
Ans:
hydrophobic and hydrophilic are the two ends of present in a soap molecule
a long hydrocarbon part which is hydrophobic and a short ionic part containing COO-Na+ which is hydrophilic
When soaps are used in hard water that contains a lot of calcium and magnesium ions they cause the soap to precipitate and it is unable to form lather.
OR
Differentiate between alkane and alkenes (any 3 differences).
Ans:
Alkane | Alkene |
They are hydrocarbons that are joined by single bonds only. Thus called saturated hydrocarbons. | They are joined by at least one double bond between them. They are reactive in nature and are called unsaturated hydrocarbons. |
The general formula is CnH2n+2. | Their general formula (not including cyclic compounds) is CnH2n. |
Examples: Methane (CH4) Ethane (C2H6) etc. | Examples: Ethene ( C2H4), Propene (C3H6) etc. |
25. The atomic numbers of the 5 elements P, Q, R, S and T are 14, 16, 11, 15 and 17 respectively. The metallic property of which of these elements is less and why? What is your conclusion on the relationship between metallic property and electro negativity?
Ans:
Element S(Cl-17) is having lowest metallic property, because. Metallic character decreases along with increasing electro negativity from left to right along the Period.
Elements with high electronegativity tend to have less metallic properties. So, the metallic properties of elements tends to decrease across a period
XI. Answer the following questions: 1x4=4
26. Explain the extraction of the metals in the middle of the activity series, with help of roasting and calcination of zinc ore.
Ans:
Metals such as iron, zinc, lead, copper, etc., are in the middle of the reactivity series. These are moderately reactive metals and are usually present as sulphides or carbonates.
Carbonate ores converted into oxides by heating strongly in limited air. This process is known as calcination.
Sulphate ores converted into oxides by heating strongly in the presence of excess of air. This process is known as roasting.
When ZnCO3 undergoes calcination ZnO if formed.
ZnCO3(s) Heat ----> ZnO(s) + 2C02(g)
When ZnS undergoes roasting ZnO is formed.
2ZnS(s) + 302(g Heat ------> ZnO(s) + 2SO2(g)
After these processes reduction is necessary.
Because zinc oxide is then reduced to zinc using suitable reducing agent.
PART C: BIOLOGY
XII. Four alternatives are given for each of the following questions. Choose the correct alternative and write the complete answer along with its letter of alphabet. 2x1=2
27. If the roots of a plant are growing towards nitrate concentrated region of the soil it is:
a) Phototropism b) hydrotropism c) thigmotropism d) chemotropism
Ans: d) chemotropism
28. Which of the following is not an environment friendly practice?
a) using own vehicle instead of public transport
b) carrying cloth bags to shop
c) rain water harvest
d) switching of unnecessary lights and fans
Ans: a) using own vehicle instead of public transport
XIII. Answer the following questions: 2x1=2
29. What is the main reason for the depletion of ozone?
Ans:
Chlorofluorocarbons or CFCs are the main cause of ozone layer depletion.
30. What is rain water harvesting?
Ans:
The process of collecting rain water during the wet season, to meet our fresh water requirements in the dry season, is called rainwater harvesting.
XIV. Answer the following questions: 3x2=6
31. Draw a labelled diagram of longitudinal section of flower.
Ans:
32. What is translocation? Why is it essential for plant?
Ans:
Translocation in plants occurs in the vascular tissue known as phloem. Translocation is the movement of materials from leaves to other tissue throughout the plants. Without translocation, the food prepared by the plant can’t reach other parts of the plant. The translocation of food (carbohydrates) occurs in the sieve tubes with the help of companion cells.
OR
What is double circulation? Why mammals and birds have four chambered heart?
Ans:
The blood flows twice through the heart and it is called double circulation.
In mammals and birds, the heart is also divided into four chambers: two atria and two ventricles, as illustrated in (Figure)d. The oxygenated blood is separated from the deoxygenated blood, which improves the efficiency of double circulation and is probably required for the warm-blooded lifestyle of mammals and birds.
33. At your home, to reduce the consumption of electricity, what measures you will take?
Ans:
· Switch off the lights, fans, television and other electrical appliances when not needed.
· Use energy efficient electrical appliances to save electricity.
· Use stairs to climb up to 3 floors of a building instead of taking a lift.
XV. Answer the following questions: 3x3=9
34. What is speciation? List the reasons for speciation?
Ans:
Speciation is the process of formation of a new species from pre-existing ones.
Reasons for speciation:
· Genetic Drift,
· Natural selection,
· Geographical isolation,
· Severe changes in DNA/change in number of chromosomes/Mutation.
OR
“Kale is evolved from wild cabbage” Explain.
Ans:
Humans have, over more than two thousand years, cultivated wild cabbage as a food plant, and generated different vegetables from it by selection This is, of course, artificial selection rather than natural selection. So some farmers have wanted to select for very short distances between leaves, and have bred the cabbage we eat. Some have wanted to select for arrested flower development, and have bred broccoli, Some have simply looked for slightly larger leaves, and come up with a leafy vegetable called kale. Would we have thought that all these structures are descended from the same ancestor.
35. How does reproduction help in providing stability to population of a species?
Ans:
Reproduction is the process of producing new individuals of the same species by existing organisms of a species, so, it helps in providing stability to population of species by giving birth to new individuals as the rate of birth must be at par with the rate of death to provide stability to population of a species.
OR
What could be the reason for adopting contraceptive methods?
Ans:
Contraceptive methods are mainly adopted because of the following reasons:
· To prevent unwanted pregnancies.
· To control population rise or birth rate.
· To prevent the transfer of sexually transmitted diseases.
36. Draw a diagram showing the structure of Nephrons and label the following parts. a) Bowman’s capsule b) collecting duct
Ans:
XVI. Answer the following questions. 2x4=8
37. i) Describe the sex determination in human beings.
ii) Give an example where sex is not genetically determined.
Ans:
i)
The males have XY sex chromosomes. They produce two types of gametes having X and Y chromosome. The females have XX chromosome. They produce only one type of gamete having X chromosome. If sperm is having X chromosome, then the child will be a girl. If sperm is having Y chromosome, then the child will be a boy.
ii)
Examples of organisms in which sex is not genetically determined are crocodiles, alligators, turtle, tuatara etc.
Incubation temperature determines sex in some of the animals like crocodiles, where the high temperature incubates maleness and low temperature produces femaleness.
38. What is reflex arc? Explain reflex action with an example.
Ans:
Reflex action is quick, sudden and immediate response of the body to a stimulus.
In some situations such as touching a hot object, pin. we need to act quickly, otherwise our body would be harmed. Here response is generated from spinal cord instead of brain. In this way, time for taking action is reduced which save us from injury.
The receptor is the organ which comes in the danger zone. The sensory neurons pick signals from the receptor and send them to the relay neuron. The relay neuron is present in the spinal cord. The spinal cord sends signals to the effector via the motor neuron. The effector comes in action, moves the receptor away from the danger.
PHYSICS
1. The sky as seen from the surface of the moon appears dark because,
Ans. : (D) atmospheric particles needed to scatter the light are not present.
- It should be a sustainable and renewable source of energy.
- It should have a high calorific value.
- It should be easily accessible and provide energy for the maximum period of time.
- It should not cause pollution.
- They have no moving parts
- Little maintenance
- Work quite satisfactorily without the use of any focusing device
- Can be set up in remote areas where people cannot reach easily
- Can set up in those areas too, where laying of power transmission line is not possible. ( Any four )
- This is used as a safety measure for appliances have metallic body in domestic circuit
- This provides a low resistance conducting path for the current
- Any leakage of current in the appliances keeps its potential to that of the earth and the user may not get a severe electric shock.
- Take a coil of copper wire having a large number of turns connect the ends of the coil to a galvanometer
- Take a strong magnet and move its one pole into the coil
- There is a deflection in the needle of the galvanometer. This indicates the presence of a current in the coil
- Likewise, when the magnet is withdrawn back then also the needle of galvanometer deflects and this indicates the presence of electric current.
V. Answer the following question : 1 × 4 = 4
- The parallel circuit divides current through the electrical gadgets.
- When one component fails, the circuit does not fail
- The total resistance in parallel circuit decreases, so that
- Electrical gadgets get current as per their resistance required. ( Any two )
- In an electrical circuit ammeter is connected in series
- In an electrical circuit voltmeter is connected in parallel
- Ammeter measures the rate of electric current in a circuit
- Voltmeter measures the potential difference across the ends of a conductor 2
- Light travelling obliquely from one medium to another, the direction of propagation of light in the second medium changes
- The incident ray, the refracted ray and the normal to the interface of two transparent media at the point of incidence all lie in the same plane
- The ratio of sine of angle of incidence to the sine of angle of refraction is constant, for the light of given colour and for the given pair of media / sini / sinr = constant
- Plaster of Paris is used in :
- Supporting fractured bones
- Making toys Decorative materials
- Making smooth surfaces. ( Any two )
- Solution A is more acidic.
- As it has more + H ions.
22. Give reason :
- Chemical displacement reaction.
- Because more reactive iron displaces copper from copper sulphate solution.
- Fe + CuSO 4 → FeSO 4 + Cu.
- Carbon compounds having same molecular formula but different structural formulae
- Molecular formula of butane is C4 H10
- Carbon has unique ability to form bonds with other atoms of carbon, giving rise to large molecules.
- General formula for alkene is Cn H 2n
- The energy that is captured by autotrophs does not revert back to the solar input.
- The energy which passes to the herbivores do not come back to autotrophs.
- As energy moves progressively through the various trophic levels it is no longer available to the previous level.
- At different levels energy is lost in the form of heat.
- Geographical isolation
- Natural selection
- Inheritance of traits
- Genetic drift / gene flow
- Variation / mutuation / changes in DNA. ( Any four )
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