CBSE Class 10 Science 2012 Question Paper

Write the name and formula of the second member of the carbon compounds having functional group - OH.

State one function of iris in human eye.

What happens when higher energy ultraviolet radiations act on the oxygen at the higher level of the atmosphere ?

In a food chain, if 10,000 joules of energy is available to the producer, how much energy will be available to the secondary consumer to transfer it to the tertiary consumer ?

Choose from the following : $6C, 8O, 10Ne, 11Na, 14Si$ (i) Elements that should be in the same period. (ii) Elements that should be in the same group. State reason for your selection in each case.

An element 'X' belongs to 3rd period and group 17 of the periodic table. State its (i) electronic configuration, (ii) valency. Justify your answer with reasoning.

Name an organism which reproduces by spore formation. List three conditions favourable for spores to germinate and grow.

State the role of placenta in the development of embryo.

To construct ray diagram we use two light rays which are so chosen that it is easy to know their directions after reflection from the mirror. List these two rays and state the path of these rays after reflection. Use these rays to locate the image of an object placed between centre of curvature and focus of a concave mirror.

Draw a labelled ray diagram to illustrate the dispersion of a narrow beam of white light when it passes through a glass prism.

A star appears slightly higher (above) than its actual position in the sky. Illustrate it with the help of a labelled diagram.

List three problems which arise due to construction of big dams. Suggest a solution for these problems.

List the products of combustion of fossil fuels. What are their adverse effects on the environment ?

What is meant by homologous series of organic compounds ? Write the chemical formulae of two members of a homologous series and state which part determines the (i) physical properties, (ii) chemical properties, of these compounds.

Na, Mg and Al are the elements having one, two and three valence electrons respectively. Which of these elements (i) has the largest atomic radius, (ii) is least reactive ? Justify your answer stating reason for each.

List and explain in brief three methods of contraception.

If we cross pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get pea plants of $F_1$ generation. If we now self-cross the pea plant of $F_1$ generation, then we obtain pea plants of $F_2$ generation. (a) What do the plants of $F_1$ generation look like ? (b) State the ratio of tall plants to dwarf plants in $F_2$ generation. (c) State the type of plants not found in $F_1$ generation but appeared in $F_2$ generation, mentioning the reason for the same.

List in tabular form two distinguishing features between acquired traits and inherited traits, with one example of each.

How are fossils formed ? Describe, in brief, two methods of determining the age of fossils.

State the types of mirrors used for (i) headlights and (ii) rear view mirrors, in cars and motorcycles. Give reason to justify your answer in each case.

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. Find the position, size and nature of the image formed, using the lens formula.

An old man cannot see objects closer than 1 m from the eye clearly. Name the defect of vision he is suffering from. How can it be corrected ? Draw ray diagram for the (i) defect of vision and also (ii) for its correction.

What are hydrocarbons ? Write the name and general formula of (i) saturated hydrocarbons, (ii) unsaturated hydrocarbons, and draw the structure of one hydrocarbon of each type. How can an unsaturated hydrocarbon be made saturated ? OR What are detergents chemically ? List two merits and two demerits of using detergents for cleansing. State the reason for the suitability of detergents for washing, even in the case of water having calcium and magnesium ions.

Distinguish between unisexual and bisexual flowers giving one example of each. Draw a diagram showing process of germination of pollen grains on stigma and label the following parts : (i) Female germ cell (ii) Male germ cell (iii) Ovary OR Draw a diagram of human female reproductive system and label the part (i) that produces eggs. (ii) where fusion of egg and sperm takes place. (iii) where zygote is implanted. What happens to human egg when it is not fertilised ?

List the new Cartesian sign convention for reflection of light by spherical mirrors. Draw a diagram and apply these conventions for calculating the focal length and nature of a spherical mirror which forms a 1/3 times magnified virtual image of an object placed 18 cm in front of it. OR With the help of a ray diagram, state what is meant by refraction of light. State Snell's law for refraction of light and also express it mathematically. The refractive index of air with respect to glass is 2/3 and the refractive index of water with respect to air is 4/3. If the speed of light in glass is $2 \times 10^8$ m/s, find the speed of light in (a) air, (b) water.

The aqueous solutions of copper sulphate and zinc sulphate appear

Solutions of copper sulphate, iron sulphate and zinc sulphate are prepared and marked I, II and III respectively. Few pieces of aluminium are added to each solution. After some time a change will be observed in

On adding 2 mL acetic acid to 2 mL of water in a test tube, it was observed that

On adding acetic acid to sodium hydrogen carbonate in a test tube, a student observes

Which one of the following are the correct observations about acetic acid ?

A student has to determine the focal length of a concave mirror by obtaining the image of a distant object on a screen. For getting best result he should focus

A student obtained a sharp inverted image of a distant tree on a screen placed in front of the concave mirror. He then removed the screen and tried to look into the mirror. He would now see

If you are to determine the focal length of a convex lens, you should have

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 ? $P_1$ and $P_2$ are the positions of pins fixed by him.

Four students showed the following traces of the path of a ray of light passing through a rectangular glass slab. The trace most likely to be correct is that of student

Following diagrams were drawn by different students on having seen prepared slides of budding in yeast. Correct diagrams are

In which of the following figures is budding not shown ?

The following figures illustrate binary fission in Amoeba in an incorrect sequence. The correct sequence is

From the following diagrams, select the correct ones showing stages of binary fission in Amoeba :

A student weighed some raisins and recorded the weight as 'x'. She then soaked the raisins in distilled water. After about 2 hours she removed the raisins, wiped them dry and weighed again and recorded that as 'y'. The percentage of water absorbed by raisins may be determined using the relationship

In the experiment for determining the percentage of water absorbed by raisins, we do the final weighing of the raisins after keeping them dipped in water for about one hour. For the accuracy of the result, the extra water from the surface of the soaked raisins is removed by