Sample Paper I

Question 1. Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Which among the following is (are) true about slaking of lime?

(i) It is an endothermic reaction

(ii) It is an exothermic reaction

(iii) The pH of the resulting solution will be more than seven

(iv) The pH of the resulting solution will be less than seven

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (i) and (iv)

(d) (iii) and (iv)

Question 2. Sodium carbonate is a basic salt because it is a salt of

(a) strong acid and strong base

(b) weak acid and weak base

(c) weak base and strong acid

(d) strong base and weak acid

Question 3. Which one of the following four metals would be displaced from the solution of its salt by other three metals?

(a) Mg

(b) Ag

(c) Zn

(d) Cu

Question 4. Which one among the following is the correct representation of electron dot structure of nitrogen

(a) N N

(b) N N

(c) N N

(d) N N

Question 5. The correct sequence of anaerobic reactions in yeast is

(a) Glucos¾e¾ ¾¾¾¾¾® cytoplasm Pyruva¾te¾ ¾¾¾¾¾¾® mitochondria Ethanol + Carbondioxide

(b) Glucos¾e¾ ¾¾¾¾¾® cytoplasm Pyruvate¾ ¾ ¾¾¾¾¾® cytoplasm Lactic acid

(c) Gluco¾se¾ ¾¾¾¾¾® cytoplasm Pyruvate¾ ¾ ¾¾¾¾¾¾® mitochondria Lactic acid

(d) Glucos¾e¾ ¾¾¾¾¾® cytoplasm Pyruvate¾ ¾ ¾¾¾¾¾® cytoplasm Ethanol + Carbondioxide

Question 6. Offspring formed as a result of sexual reproduction exhibit more variations because

(a) sexual reproduction is a lengthy process

(b) genetic material comes from two parents of the same species

(c) genetic material comes from two parents of different species

(d) genetic material comes from many parents

Question 7. New species may be formed if

(i) DNA undergoes significant changes in germ cells

(ii) chromosome number changes in the gamete

(iii) chromosome number remains the same

(iv) mating does not take place

(a) (i) and (ii)

(b) (i) and (iii)

(c) (ii), (iii) and (iv)

(d) (i), (ii) and (iv)

Question 8. Beams of light are incident through the holes A and B and emerge out of the box through the holes C and D respectively as shown in the Figure. Which of the following could be inside the box?

(a) a rectangular glass slab

(b) a convex lens

(c) a concave lens

(d) a glass prism

Question 9. The clear sky appears blue because

(a) blue light gets absorbed in the atmosphere.

(b) ultraviolet radiations are absorbed in the atmosphere.

(c) violet and blue lights get scattered more than all other colours by the atmosphere.

(d) light of all other colours is scattered more than the violet and blue colour lights by the atmosphere.

Question 10. Identify the given circuit in which the electrical components have been properly connected.

(a) (i)

(b) (ii)

(c) (iii)

(d) (iv)

Question 11. The resistance between A and B in the given Figure will be

(a) $20 \, \Omega$

(b) $30 \, \Omega$

(c) $90 \, \Omega$

(d) more than $10 \, \Omega$ but less than $20 \, \Omega$

Question 12. In the arrangement shown in given Figure, there are two coils wound on a non-conducting cylindrical rod. Initially the key is not inserted. Then the key is inserted and later removed. Then

(a) the deflection in the galvanometer remains zero throughout

(b) there is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the key is removed

(c) there are momentary galvanometer deflections that die out shortly; the deflections are in the same direction

(d) there are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions

Question 13. A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in the given Figure. The direction of magnetic field at a point will be North to South

(a) directly above the wire

(b) directly below the wire

(c) at a point located in the plane of the paper, on the north side of the wire

(d) at a point located in the plane of the paper, on the south side of the wire

Question 14. The major problem in harnessing nuclear energy is how to

(a) split nuclei

(b) sustain the reaction

(c) dispose off spent fuel safely

(d) convert nuclear energy into electrical energy

Question 15. Which of the statements is incorrect?

(a) All green plants and blue green algae are producers

(b) Green plants get their food from organic compounds

(c) Producers prepare their own food from inorganic compounds

(d) Plants convert solar energy into chemical energy

Question 16. Write the balanced chemical equations for the following reactions and identify the type of reaction in each case

(a) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773K to form ammonia gas.

(b) Limestone is heated strongly to form quicklime and carbondioxide gas is evolved

Question 17. Salt A commonly used in bakery products on heating converts into another salt B which is used in the manufacture of glass and a gas C is evolved. The gas C when passed through lime water, turns it milky. Identify A, B and C. Write the reaction for heating of salt A.

Question 18. Properties of the elements are given below. Where would you locate the following elements in the Periodic Table?

(a) A soft metal stored under kerosene

(b) An element with variable (more than one) valency stored under water.

Question 19. Why is ‘nutrition’ a necessity for an organism?

Question 20. Why is the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron but not the reverse?

Question 21. In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation.

Question 22. Sudha finds out that the sharp image of the window pane of her science laboratory is formed at a distance of 15 cm from the lens. She now tries to focus the building visible to her outside the window instead of the window pane without disturbing the lens. In which direction will she move the screen to obtain a sharp image of the building? What is the approximate focal length of this lens?

Question 23. A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw ray diagram for the correction of this defect.

Question 24. How will you use two identical prisms so that a ray of white light incident on one prism emerges out of the second prism as white light? Draw the diagram.

Question 25. Three 60 W incandescent bulbs are connected in a parallel.

(a) Calculate the total power consumed.

(b) Now suppose that one of the bulbs is fused. What will be the total power consumed now?

Question 26. A magnetic compass shows a deflection when placed near a current carrying wire. How will the deflection of the compass get affected if the current in the wire is increased? Support your answer with a reason.

Question 27. What is the difference between the direct and alternating currents? How many times does AC used in India change direction in one second?

Question 28. What steps would you suggest to minimise environmental pollution caused by burning of fossil fuels?

Question 29. List the common food chain of a pond ecosystem

Question 30. List two advantages associated with water harvesting at the community level.

Question 31. Explain the following

(a) The reactivity of a piece of aluminium metal decreases if it is dipped in HNO$_{3}$

(b) Carbon cannot reduce the oxides of Na or Mg

(c) NaCl does not conduct electricity in solid state whereas it does conduct electricity in aqueous solution as well as in molten state

(d) Necessity of galvanisation of iron articles

(e) Metals like Na, K, Ca and Mg are never found in their free state in nature.

Question 32. You are given the balls and sticks models of six carbon atoms and fourteen hydrogen atoms and sufficient number of sticks. In how many ways one can join the models of six carbon atoms and fourteen hydrogen atoms to form different molecules of C$_{6}$H$_{14}$.

or

Draw structural formulae of all the possible isomers of the compound with molecular formula C$_{3}$H$_{6}$O and also give their electron dot structures.

Question 33. Distinguish between pollination and fertilisation. Mention the site and product of fertilisation in a flower. Draw a neat, labelled diagram of a pistil showing pollen tube growth and its entry into the ovule.

or

Reproduction is essentially a phenomenon that is not for survival of an individual but for continuation of a species. Justify

Question 34. (a) Draw ray diagrams showing the image formation by a convex lens when an object is placed

(i) at twice the focal length of the lens

(ii) at infinity

(b) The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. If the image is three times the size of the flame and the distance between lens and image is 80 cm, at what distance has the candle been placed from the lens? What is the nature of the image and the lens?

or

Write laws of refraction of light. Explain the same with the help of ray diagram, when a ray of light passes through a rectangular glass slab

Question 35. How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistances in series connected to a battery?

or

Find out the following in the electric circuit given in the Figure.

(a) Effective resistance of two $8 \, \Omega$ resistors in combination.

(b) Current flowing through $4 \, \Omega$ resistor.

(c) Potential difference across $4 \, \Omega$ resistor.

(d) Power dissipated by $4 \, \Omega$ resistor.

(e) Difference in ammeter readings, if any.

Question 36. In the context of conservation of natural resources, explain the terms reduce, recycle and reuse. From among the materials that we use in daily life, identify two materials for each category.

or

Suggest a few useful ways of utilising waste water.