CBSE Class 10 Science 2012 Question Paper

Write the name and formula of the first member of the series of carbon compounds having functional group - C - OH.

State one function of the crystalline lens in the human eye.

What is the function of ozone at the higher level of atmosphere?

Consider the following food chain which occurs in a forest: Grass → Deer → Lion. If 10000 J of solar energy is available to the grass, how much energy would be available to the deer to transfer it to the lion?

Consider the following elements: $4\text{Be}, 9\text{F}, 19\text{K}, 20\text{Ca}$. Choose from the following: (i) The element having one electron in the outermost shell. (ii) Two elements of the same group.

An element has atomic number 13. (a) What is the group and period number to which this element belongs? (b) Is this element a metal or a non-metal? Justify your answer.

List two advantages of practising vegetative propagation in plants. Select two plants raised by this method from the list given below: banana, gram, pea, rose, tomato, wheat

List the parts of human male reproductive system which contribute fluid to the semen. State two advantages semen offers to the sperms.

To construct a ray diagram we use two light rays which are so chosen that it is easy to know their directions after refraction from the lens. List these two rays and state the path of these rays after refraction. Use these two rays to locate the image of an object placed between ‘f’ and ‘2f’ of a convex lens.

Draw a ray diagram to show the formation of a rainbow and mark the point where (i) dispersion, (ii) internal reflection occurs.

“The time difference between the actual sunset and the apparent sunset is about 2 minutes.” What is the reason for the same? Explain with the help of a diagram.

Why are forests considered “biodiversity hot spots”? List two ways in which an individual can effectively contribute to the management of forests and wildlife.

State the meaning of “sustainable management”. Reuse is better than recycling. How?

Distinguish between esterification and saponification reactions of organic compounds with the help of the chemical equation for each. What is the use of (i) esters and (ii) saponification process?

(a) How many periods are there in the modern periodic table of elements? (b) How do atomic radius, valency and metallic character vary down a group? (c) How do the atomic size and metallic character of elements vary as we move from left to right in a period?

What is AIDS? Which microbe is responsible for AIDS infection? State one mode of transmission of this disease. Explain in brief one measure for the prevention of AIDS.

"An individual cannot pass on to its progeny the experiences of its life-time." Justify the statement with the help of an example and also give reason for the same.

(i) We see eyes in planaria, insects, octopus and vertebrates. Can eyes be grouped together in case of the above-mentioned animals to establish a common evolutionary origin? Why? (ii) State one evidence to prove that birds have evolved from reptiles.

With the help of a flow chart explain in brief how the sex of a newborn is genetically determined in human beings. Which of the two parents, the mother or the father, is responsible for determination of sex of a child?

Name the type of mirror used in the following situations: (i) Headlights of a car (ii) Rear-view mirror of a vehicle (iii) Solar furnace. Support your answer with reason.

A 4 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 24 cm. The distance of the object from the lens is 16 cm. Using lens formula, find the position, size and nature of the image formed.

Draw a diagram to show why distant objects cannot be seen distinctly by a myopic eye. List two reasons due to which this defect of vision may be caused. A person with a myopic eye cannot see objects clearly beyond a distance of 2 m. Name the type of the corrective lens that would be needed to correct the defect of vision and draw a ray diagram to show how the defect gets corrected.

(a) With the help of a suitable example, explain the process of hydrogenation mentioning the conditions of the reaction and any one change in physical property with the formation of the product. (b) How does a saturated hydrocarbon react with chlorine? Write chemical equation for it. What type of reaction is it called and why? OR What are soaps and detergents chemically? Explain the action of cleaning by soaps. State the reason why we can wash our clothes even in hard water using detergents.

(i) Explain with the help of a diagram how pollen after landing on the stigma of a flower helps male germ cell to reach the female germ cell. Label the following: ovary, female germ cell, male germ cell and pollen grain. (ii) State the meaning of pollination and mention a distinguishing feature between self-pollination and cross-pollination. OR State in brief the changes that take place in a fertilized egg (zygote) till birth of the child in the human female reproductive system. What happens to the egg when it is not fertilized?

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 spherical lens which forms three times magnified real image of an object placed 16 cm from the lens. OR State the laws of refraction of light. Write an expression to relate absolute refractive index of a medium with speed of light in vacuum. The refractive index of a medium ‘x’ with respect to ‘y’ is 2/3 and the refractive index of medium ‘y’ with respect to ‘z’ is 4/3. Calculate the refractive index of medium ‘z’ with respect of ‘x’.

Some crystals of ferrous sulphate were dissolved in distilled water. The colour of the solution obtained was

A student puts one big iron screw each in four test tubes containing aqueous solutions of aluminium sulphate, copper sulphate, ferrous sulphate and zinc sulphate. After some time he observed a reddish brown coating only on the surface of the screw which was put in the solution of

Acetic acid smells like:

In a litmus test it is observed that an aqueous solution of acetic acid turns

A student takes four test tubes marked a, b, c and d containing NaCl, Na₂CO₃, NaHCO₃ and NaOH respectively. He adds acetic acid to the test tubes one by one and every time he immediately brings a lighted match-stick near to the mouth of the test tube. He observes that the match-stick extinguishes in the cases of

Parallel light rays from a distant object incident on a device 'X' form a point size image on a screen. The device 'X' must be

A student has to determine the focal length of a convex lens by obtaining the image of a distant object on a screen. Which of the following measures should he take to obtain better results? a. Select a lens of small diameter (say 3 cm). b. Select a lens of larger diameter (say 5 cm). c. Select an object very far from the lens. d. Select an object far, but not very far, from the lens. e. Keep all the lights of the room on. f. Keep minimum lights of the room on.

Three students X, Y and Z are finding the focal length of the given concave mirror by obtaining the image of the object selected by them. X obtains the image of the grill of the nearest window of the lab. Y obtains the image of a white painted building near the lab and Z obtains a point size image of the sun. The most correct value of the focal length is obtained by

The values of ∠i, ∠r and ∠e as measured by four students P, Q, R and S are tabulated below: The student who performed the experiment most carefully and methodically is

While performing the experiment on tracing the path of a ray of light through a rectangular glass slab, in which of the following experimental set-ups is a student likely to get best results? (P₁ and P₂ are the positions of the pins fixed for the experiment)

After observing a slide, a student draws the following diagrams for different stages of binary fission in Amoeba which are not given in a correct sequence here. The correct sequence of these diagrams should be

A student draws the following diagram after observing a prepared slide under a microscope. This illustrates

A prepared slide of budding in yeast was shown to the students of a class. Different students made different sketches on the basis of their memory. Out of these, four diagrams are shown below: The correct diagram(s) is/are

While performing an experiment with raisins, a student took the following measurements: Mass of water taken in the beaker = 25 g, Mass of raisins before soaking = 5 g, Mass of raisins after soaking = 8 g, Mass of water left in the beaker after experiment = 21 g. The percentage of water absorbed by raisins is

While performing the experiment of determining the percentage of water absorbed by raisins, the extra water left on the surface of soaked raisins is removed before final weighing. The correct procedure for this is

Following are the steps involved in the experiment of determining the percentage of water absorbed by raisins which are not in proper sequence: a. Weigh soaked raisins, b. Weigh dry raisins, c. Soak the raisins in water for 2 hours, d. Wipe out soaked raisins gently. The correct sequence of these steps is