KSEEB - 10 SCIENCE - MODEL QUESTION PAPER - 4 - KEY ANSWER

           KSEEB - 10 SCIENCE             

           MODEL QUESTION PAPER - 4 (25-26)    

                     KEY ANSWER                 

                 PART - A PHYSICS        

I. Multiple choice questions: 2 × 1 = 2

1. The diameter of the reflecting surface of a spherical mirror is    

 (A) pole of the mirror 

 (B) centre of curvature 

 (C) principal axis 

 (D) aperture

Ans: (D) aperture

2. When three resistors of different resistance are connected in parallel in an electric circuit and switched on, then the quantity that remains the same in all the resistors is 

(A)  current 

(B) potential difference 

(C) resistance 

(D) resistivity   

Ans: (B) potential difference

II. Answer the following questions: 2 × 1 = 2

3. What are the reasons for overload in an electric circuit?

Ans:

★ Accidental hike in the supply voltage.

★ Connecting too many appliances to a single socket.

★ When live wire and neutral wire come into direct contact. ( Any two )

4. Two situations of freely suspended parallel copper wires carrying current are shown in the figure given below.

In which of these situations, the wires attract each other? Justify your answer. 

Ans:

★ Situation – 1

★Parallel wires carrying currents in the same direction attract each other. Therefore, in this situation, the two wires attract each other.

III. Answer the following questions: 3×2 =6

5. What is the colour of danger signal lights? Why is that colour preferred?

Ans:

★ The colour of danger signal lights is red.

★ Because it has the longest wavelength among visible colours so, it gets scattered the least by dust, fog, or air molecules.

6. Among nichrome and copper wires, which of the wires is used in electric fan and in the coils of electric heater? Why?

Ans:

★ Copper wire is used in the electric fan because It has low resistivity.

★ Nichrome wire is used in the coils of the electric heater because It has high resistivity and high melting point.

7. Draw the diagram indicating the field lines of the magnetic field around a current carrying straight conductor.

Ans:

IV. Answer the following questions : 3×3=9

8. Draw the ray diagram to show the image formation when an object is kept between ‘C’ and ‘F’ of a concave mirror. Write the nature and size of the image formed. [C = Centre of curvature, F = Principal Focus]

Ans:

Size of the image: Larger

Nature of the image : read and inverted.

9. Explain an experiment to demonstrate that a current carrying conductor placed in a magnetic field experiences a force. 

OR 

Explain an activity to draw the magnetic field lines around a bar magnet using a compass needle.

Ans:

★ Take a small aluminium rod and suspend it horizontally using connecting wires.

★ Place a strong horse-shoe magnet in such a way that rod lies between the two poles with the magnetic field directed upwards. 

★ Connect the aluminium rod in series with a battery, a key and a rheostat. 

★ Now pass the current through the aluminium rod in one particular direction. 

★ The rod displaces towards one side. 

★ Reverse the direction of current flowing through the rod. The rod displaces towards the opposite side.  

OR

★ Place a bar magnet on a white paper and mark the boundary of the magnet 

★ Place the compass needle near the north pole of the magnet. The south pole of the compass needle directs towards the north pole of the magnet. Mark it with a point. 

★ Move the needle to a new position such that its south pole occupies the position previously occupied by its north pole. Mark it with a point. 

★ In this way proceed step by step till you reach the south pole of the magnet. 

★ Join the points marked on the paper by a small curve. 

★ This curve represents a field line

10. A student clearly reads letters of a textbook only when the book is kept at a distance more than 50 cm from his eyes without difficulty. Then, 

i) identify this defect of the eye. 

ii) suggest a remedy for this defect.

b) When sunlight passes through the trees of a dense forest on a foggy morning then the path of the beam of light appears between the trees. 

i) What is this phenomenon called? 

ii) The same phenomenon is not normally visible in an open field. Why? Write your analysis.

OR 

a) The position of the stars changes apparently in the clear sky. Why? Explain. 

b) White light is passed through the given arrangement of three glass prisms (X, Y, and Z) as shown in the figure given below.

i) Is spectrum of light seen on the screen? 

ii) What is the role of prism Z?

Ans:

a) 

i) defect is Hypermetropia

ii) This defect is corrected by using a  convex lens

b)

i) This is called the Tyndall effect

ii) In an open field, the air is usually clearer and contains fewer suspended particles. Since scattering is very low, the light does not become visible as a beam.

OR

a)

★ It is due to atmospheric refraction of starlight. 

★ The starlight on entering the earth’s atmosphere, undergoes refraction continuously before it reaches the earth. 

★ The atmospheric refraction occurs in a medium of gradually changing refractive index 

★ As the path of rays of light coming from the star goes on varying slightly, the apparent position of the star fluctuates and the amount of starlight entering the eye flickers. This is the twinkling effect of stars.  

b)

i) Yes / The spectrum of light forms on the screen

ii) Prism Z disperses this white light into 7 colours and hence we see the spectrum of light on the screen.  

V. Answer the following questions: 2×4 = 8

11. a) What is magnification? Write the formula to calculate magnification of the image produced by a lens.

b) State the laws of reflection of light.

Ans:

a)

★ It is the ratio of the height of the image to the height of the object.

★ M = h'/h = v/u

b)

i) The angle of incidence is equal to the angle of reflection. 

ii) The incident ray, the normal to the mirror at the point of incidence and the reflected ray, all lie in the same plane 

12. a) Two resistors of resistance 10Ω and 40Ω are connected in series and connected to a 12V battery. Calculate the equivalent resistance in the electric circuit and the total current flowing in the circuit. 

b) A washing machine rated 500W is used for 2 hours a day for 30 days. Calculate the cost of using this appliance at 3 Rs per 1 kWh. 

OR 

a) Resistance of a metal wire of length 2 m is 28 Ω at 20°C. If the diameter of the wire is 0.04 mm then, what will be the resistivity of the metal at that temperature? 

b) 1000 J of heat is produced each 2 seconds in a 5Ω resistor. Find the potential difference across the resistor.

Ans:

a)

Given: 

R1 = 10 Ω

R2 = 40 Ω

V = 12 V

Equivalent Resistance: 

Rs = R1 + R2 = 10 + 40 = 50 Ω

Total Current:

I = V / Rs

I = 12 / 50 

I =  0.24 A

b)

Given:

P = 500W = 0.5 kW

t = 2h × 30 days = 60h

E = P × t 

E = 0.5kW × 60h = 30kWh

Cost = 30kWh × 3Rs = 90Rs

OR

a)

b)

Given:

H = 1000j

R = 5Ω

t = 2s

H = I2 R T

I2 = H/Rt

I = √ 1000/5×2 = 10 A

V = I R = 10A × 5 = 50V

                  PART - B CHEMISTRY        

VI. Multiple choice questions:   3 × 1 = 3 

13. As the pH value of a neutral solution increases, 

(A)    basic property decreases and number of OH− ions increases. 

(B) acidic property increases and number of H+ ions decreases. 

(C)  basic property increases and number of OH− ions increases. 

(D) acidic property decreases and number of H+ions increases. 

Ans: (C) basic property increases and number of OH− ions increases. 

14. The X in the following reaction represents, 

(A)  K2Cr2O7               (B) KMnO4 

(C) NaOH                     (D) KOH 

Ans: (B) KMnO4

15. To make pure iron hard and strong, the substance that is to be added to it is 

(A)  carbon       (B)  zinc     

(C) nickel           (D) tin

Ans: (A) carbon

VII. Answer the following questions: 3×1= 3

16. What is rancidity?

Ans: Rancidity is the process of oxidation of oils and fats in food materials, which leads to a change in their smell and taste.

17. Write the structural formula of the compound obtained when one atom of hydrogen in ‘ethane’ is replaced by −CHO group. 

Ans:

18. Aluminium articles do not corrode easily like iron articles. Justify.

Ans:

Because aluminium reacts with the oxygen in the air to form a thin, strong, and protective layer of aluminium oxide  on its surface. This oxide layer is highly resistant to further corrosion.

VIII. Answer the following questions: 3×2=6

19. Analyze the list of experiments in the table given below. In which of the experiments the following salts will be produced? (i)  An acidic salt (ii) A neutral salt 

Ans:

i) Experiment No 1

ii) Experiment No 3

20. Name the catalyst used and the product obtained in the hydrogenation of ethene. 

OR 

The molecular formula of the first member of a homologous series of carbon compounds is CH2O(HCHO). Determine the name and the molecular formula of the third member of this group. Mention the general name of this group.

Ans: 

★ Nickel (Ni) / Palladium (Pd)

★ Ethane 

21. Draw the diagram to show the action of steam on metals.  

Ans:

IX. Answer the following questions: 3×3 = 9 

22. Write the balanced chemical equations for the following reactions. 

a) Calcium carbonate → Calcium oxide + carbon dioxide 

b) Hydrogen + chlorine → Hydrogen chloride 

c) Magnesium + hydrochloric acid → Magnesium chloride + Hydrogen 

Ans:

a) CaCO3    →   CaO  +  CO2

b) H2   +  Cl2  →   2HCl

c) Mg  +  2HCl   →   MgCl2   +  H2

23. What is neutralization? Name the acid present in the following substances. i) Curd ii)Gastric juice 

Ans:

Reaction in which an acid reacts with a base to form salt and water

i) Lactic acid

ii) Hydrochloric acid

24. Explain the formation of ionic bond between sodium and chlorine atoms. 

OR 

a) Write the chemical reactions to prove that aluminium oxide is an amphoteric oxide. 

b) How calcination differs from roasting?

Ans:

OR

a) 

★  Al2O3   +    6HCl → 2AlCl3   +  3H2O

★   Al2O3  + 2NaOH → 2NaAlO2   + H2O

b)

★ Carbonate ores are converted into oxides by heating strongly in limited air. This process is known as calcination. 

★ Sulphide ores are converted into oxides by heating strongly in the presence of excess of air. This process is known as roasting. 

X. Answer the following question: 1 × 4 = 4

25. a) Give reasons: 

i)  Carbon atoms neither form C4 - anion nor form C4+ cation. 

ii) Ethanoic acid known as glacial acetic acid.  

b) Write the structural formula of the following carbon compounds: i)  Butyne ii) Cyclohexane 

OR 

a) Explain the mechanism of cleansing action of soaps. 

b) Write the differences between saturated and unsaturated carbon compounds.

Ans:

a)

i)   

★ Carbon cannot form C4+ cation because of removal of 4 elections from a carbon atom would require a large amount of energy.

★ Carbon cannot form C4- anion because it would be difficult for the nucleus with 6 protons to hold on to 10 electrons.

ii)

The melting point of pure ethanoic acid is very low / 290 K and hence it freezes during winter / in cold climates. 

b)

i)

ii)

OR

a) 

★ The molecules of soap are sodium or potassium salts of long chain carboxylic acids.

★ The ionic end of soap interacts with water while the carbon chain interacts with oil.

★ The soap molecules thus form structure called micells. This forms an emulsion in water.

★ The soap micelles thus helps in pulling out the dirt in water and we can wash our clothes clean.

b)

                 PART - C BIOLOGY        

XI. Multiple Choice Questions: 3× 1 = 3 

26. The process of producing new individuals in rhizopus is 

(A)    spore formation  (B) fragmentation 

(C) budding                   (D) regeneration 

Ans: (A) spore formation

27. Part of flower that develops into fruit and part of the seed that develops into root respectively are 

(A)  Ovary and Plumule 

(B) Plumule and radicle 

(C)  Ovary and radicle 

(D) Ovary and ovule

Ans: (C) Ovary and radicle 

28. Organisms that reproduce sexually are more likely to survive in their environment. Because in sexual reproduction these organisms, 

(A)    do not produce any variations. 

(B) will not have any errors during DNA replication. 

(C) will have the same body structure in all generations. 

(D) will have the maximum number of successful variations in the subsequent generations. 

Ans: (D) will have the maximum number of successful variations in the subsequent generations. 

XII. Answer the following questions:3 ×1 = 3 

 

29. What is the function of synapse?

Ans:

It transmits chemical signals generated at the axon terminal to the dendrite

30. Is self-pollination possible in flowers that have only stamens? Justify your answer. 

Ans:

No, For self-pollination to occur, a flower must have both stamens (male part) and pistil/carpel (female part).

31. The respiration rate of aquatic animals is faster than that is found in terrestrial animals. Why?

Ans:

Because the amount of dissolved oxygen is fairly low as compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms. 

XIII. Answer the following questions: 2×2=4 

32. What is geotropism? Name the plant part that is positively geotropic. 

OR 

Name the hormones that perform the following functions in humans. 

i) Controlling the level of sugar in the blood. 

ii) Preparing the body to face the emergency situation. 

Ans:

★ The growth movement of a plant part in response to the force of gravity.

★ The root

OR

i) Insulin

ii) adrenaline

33. The approximate lengths of the small intestine of the animals A and B are given in the below table. Observe the data in the table and answer the question.  

Identify the herbivorous and carnivorous animal among A and B. Support your conclusion. 

Ans:

★ Animal X is herbivorous and animal Y is carnivorous.

★Because herbivores consume plant which is full of cellulose and the digestion of cellulose takes a long time. Herbivores need a longer small intestine to allow cellulose to be digested.

★ Whereas Meat is easier to digest, hence carnivores have shorter small intestine.

XV. Answer the following questions: 3×3= 9

34. a) Define the following: 

i)  Food chain 

ii) Biomagnification 

b) Mention the function of ozone. Name the chemical responsible for ozone depletion.  

Ans:

a)

i) It is the sequence of organisms through which energy is transferred from one trophic level to the next,

ii) It is the phenomenon where the concentration of a non-biodegradable  progressively increases at successive trophic levels in a food chain

b) 

★ Ozone protects the earth from harmful UV-radiation 

★ CFC‘s are responsible for the decrease in the amount of ozone layer.

35. a) A short pea plant (tt) is crossed with a tall pea plant (TT). Express the result obtained in the F2 generation with the help of checkerboard. 

b) How is the baby girl sex will be determined? 

 OR 

Round and yellow seeds (RrYy) producing pea plants are self-pollinated. Express the result obtained in this crossing with the help of a checkerboard. Mention the types of the plants obtained. 

Ans:

a)

b)

★ male has one X and one Y chromosome (XY).

★ The female produces only one type of gamete (ovum) with an X chromosome.

★ A child who inherits X chromosome from her father will be a baby girl.

OR

The plants obtained are

Round yellow — 9 ,

Wrinkled yellow — 3 ,

Round green — 3

Wrinkled green — 1

36. In a situation where we withdraw our leg when stepped on thorn unknowingly, 

i)  Write the sequences of events that occur to give the response in this situation. 

ii) Which part of human nervous system controls this action?

Ans:

i) 

★ Receptors receive the stimulus of pain

★Messages reach spinal cord through sensory neuron.

★Responses reach motor neuron through association neuron.

★Responses reach effectors through motor neuron.

★ Muscles withdraw the leg.

ii) Spinal cord controls this action  

XVI. Answer the following question: 1×4 = 4 

37. Draw the diagram showing the structure of the human heart. Label the following parts: i)  Superior vena cava ii) Left ventricle 

Ans:

XVII. Answer the following question :1x5= 5 

38. a) What happens if egg does not fertilize in human female reproductive system? Explain briefly. 

b) List any four advantages of vegetative propagation. 

c) Write two examples for the organisms that reproduce by binary fission.  

OR 

a) In women, how does a fertilized egg develop into an embryo in the uterus? 

b) Is surgical contraception a better method of contraception than physical contraception? Justify your answer. 

c) Write the function of testes in human male reproductive system. 

Ans:

a)

★Uterus prepares itself every month to receive fertilized egg. It makes its inner layer thick and spongy.

★ If fertilization doesn‘t occur the lining slowly breaks and comes out through the vagina as blood and mucous. ( Menstruation occurs )

b)

★Good qualities of a variety can be maintained indefinitely.

★Vegetative propagation gives a genetically uniform population.

★ Plants raised by vegetative propagation can bear flowers and fruits earlier.

★ This makes the propagation of plants that have lost the capacity to produce seeds 

c)

★ Amoeba

​

★ Paramecium 

★ Leishmania      (Any two)

OR

a)

★ The fertilized egg starts dividing and forms a ball of cells or embryo.

★ The embryo is implanted in the lining of the uterus where they continue to grow and develop organs to become foetus.

b)

★ Yes

★Surgical contraception more effective and permanent than physical (barrier) methods like condoms or diaphragms

c) They produce sperms and testosterone hormone which is responsible for male characters.