CBSE Class 10 Science 2011 Question Paper

How many covalent bonds are there in a molecule of ethane, $\text{C}_2\text{H}_6$?

What is Tyndall effect?

What will happen if we kill all the organisms in one trophic level?

(i) How do you calculate the possible valency of an element from the electronic configuration of its atoms? (ii) Calculate the valency of an element X whose atomic number is 9.

How does the electronic configuration of an atom of an element relate to its position in the modern periodic table? Explain with one example.

What is meant by the dispersion of white light? Draw a diagram to show dispersion of white light by the glass prism.

Write any two differences between binary fission and multiple fission in a tabular form as observed in cells of organisms.

Explain giving one example of each, the unisexual and the bisexual flowers.

What are non-renewable resources of energy? Give two examples of such resources.

Write one chemical equation to represent each of the following types of reactions of organic substances: (i) Esterification (ii) Saponification (iii) Substitution

Draw the ray diagram and also state the position, the relative size and the nature of image formed by a concave mirror when the object is placed at the centre of curvature of the mirror.

Define, 'refractive index of a transparent medium.' What is its unit? Which has a higher refractive index, glass or water?

What eye defect is hypermetropia? Describe with a ray diagram how this defect of vision can be corrected by using an appropriate lens.

(a) List two sexually transmitted diseases in each of the following cases: (i) Bacterial infections (ii) Viral infections (b) How may the spread of such diseases be prevented?

Explain with examples how the following are evidences in favour of evolution in organisms: (i) Homologous organs (ii) Analogous organs (iii) Fossils

Explain the terms: (i) Speciation (ii) Natural selection

Explain how equal genetic contribution of male and female parents is ensured in the progeny.

(a) In a tabular form, differentiate between ethanol and ethanoic acid under the following heads: (i) Physical state (ii) Taste (iii) $\text{NaHCO}_3$ test (iv) Ester test (b) Write a chemical reaction to show the dehydration of ethanol. OR (a) What is a soap? Why are soaps not suitable for washing clothes when the water is hard? (b) Explain the action of soap in removing an oily spot from a piece of cloth.

(a) If the image formed by a lens is diminished in size and erect, for all positions of the object, what type of lens is it? (b) Name the point on the lens through which a ray of light passes undeviated. (c) An object is placed perpendicular to the principal axis of a convex lens of focal length $20\text{ cm}$. The distance of the object from the lens is $30\text{ cm}$. Find (i) the position (ii) the magnification and (iii) the nature of the image formed. OR (a) One-half of a convex lens is covered with a black paper. Will such a lens produce an image of the complete object? Support your answer with a ray diagram. (b) An object $5\text{ cm}$ high is held $25\text{ cm}$ away from a converging lens of focal length $10\text{ cm}$. (i) Draw the ray diagram and (ii) Calculate the position and size of the image formed. (iii) What is the nature of the image?

(a) Draw a diagram of the longitudinal section of a flower and label on it sepal, petal, ovary and stigma. (b) Write the names of male and female reproductive parts of a flower. OR (a) What is fragmentation in organisms? Name a multicellular organism which reproduces by this method. (b) What is regeneration in organism? Describe regeneration in Planaria with the help of a suitable diagram.

To find the focal length of a concave mirror Rahul focuses a distant object with this mirror. The chosen object should be:

For finding the focal length of a convex lens by obtaining the image of a distant object, one should use as the object:

Mohan obtained a sharp inverted image of a distant tree on the screen placed behind the lens. He then moved the screen and tried to look through the lens in the direction of the object. He would see:

Four students A, B, C and D traced the paths of incident ray and the emergent ray by fixing pins P and Q for incident ray and pins R and S for emergent ray for a ray of light passing through a glass slab. The correct emergent ray was traced by the student:

Rahim recorded the following sets of observations while tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence. $$\begin{array}{|c|c|c|c|} \hline \text{S. No.} & \text{Angle of incidence} & \text{Angle of refraction} & \text{Angle of emergence} \\ \hline \text{I} & 45^\circ & 41^\circ & 45^\circ \\ \hline \text{II} & 40^\circ & 38^\circ & 38^\circ \\ \hline \text{III} & 45^\circ & 41^\circ & 40^\circ \\ \hline \text{IV} & 41^\circ & 45^\circ & 41^\circ \\ \hline \end{array}$$ The correct observation is recorded at serial number:

The colour of an aqueous solution of zinc sulphate as observed in the laboratory is:

To show that zinc is a more active metal than copper, the correct procedure is to:

Acetic acid smells like:

Acetic acid solution turns:

On adding $\text{NaHCO}_3$ to acetic acid, a gas is evolved which turns lime water milky due to the formation of:

A yeast cell in which budding occurs was seen to have:

A student was given two permanent slides, one of binary fission in amoeba and other of budding in yeast. He was asked to identify any one difference in the nucleus of the two. One such difference, he identified correctly was:

Binary fission is observed in which one of the following figures?

To determine the percentage of water absorbed by raisins, raisins are soaked in water for:

Raisins are wiped off gently before final weighing with help of:

The step(s) necessary for determining the percentage of water absorbed by raisins is/are: