Board Paper of Class 10 2011 Science (SET 3) - Solutions

What are the various steps in a food chain called?

What is the important function of presence of ozone in earth’s atmosphere?

Write the electron dot structure of ethane molecule, C₂H₆.

What makes the earth’s atmosphere a heterogeneous mixture?

List any four characteristics of a good fuel.

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

(i) How do you calculate the possible valency of an element from the electronic configuration of its atoms?

(ii) Calculate the valency of element X whose atomic number is 9.

On the basis of electronic configuration, how will you identify the first and the last element of a period?

State the two laws of reflection of light.

The stars appear higher from horizon than they actually are. Explain why it is so.

Explain why the planets do not twinkle but the stars twinkle.

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

Why is DNA copying an essential part of the process of reproduction?

Explain the terms:

(i) Speciation

(ii) Natural selection

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

Out of HCl and CH₃COOH, which one is a weak acid and why? Describe an activity to support your answer.

Two elements X and Y belong to group 1 and 2 respectively in the same period of periodic table. Compare them with respect to:

(i) the number of valence electrons in their atoms

(ii) their valencies

(iii) metallic character

(iv) the sizes of their atoms

(v) the formulae of their oxides

(vi) the formulae of their chlorides

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.

(i) “The refractive index of diamond is 2.42”. What is the meaning of this statement?

(ii) Name a liquid whose mass density is less than that of water but it is optically denser than 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 disease in each of the following cases:

(i) Bacterial infections

(ii) Viral infections

(b) How may the spread of such diseases be prevented?

Explain Mendel’s law of independent inheritance. Give one example.

(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 cm. The distance of the object from the lens is 30 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 cm high is held 25 cm away from a converging lens of focal length 10 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.

(a) In a tabular form, differentiate between ethanol and ethanoic acid under the following heads:

(i) Physical state

(ii) Taste

(iii) NaHCO₃ 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.