KREIS - Science Model Question Paper - 5 with Answer

Key Answer

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

II. Answer the following questions:                                                                          2x1=2

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

2^nd 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.

ZnCO_3(s)       ^Heat  ---->     ZnO_(s) + 2C0_2(g)

When ZnS undergoes roasting ZnO is formed.

2ZnS_(s) + 30_2(g    ^Heat ------>     ZnO_(s) + 2SO_2(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.