Metals and Non-Metals — Science STD 10 — Question

Write a short note on ‘Chipko Andolan’ (Hug the Trees Movement).

X, Y, and Z are three animals. The animal X can fly but animal Y can only run on ground or walls. The forelimbs of animals X and Y have the same basic design but they are used for different purposes such as flying and running respectively. The animal Z became extinct an long time ago. The study of fossils of Z tells us that it had some features like those of X and some like those of Y. In fact, Z is said to form a connecting link in the evolutionary chain of X and Y.

1. What could the animals X, Y and Z be?
2. What name is given to the forelimbs like those of X and Y which have the same basic design but different functions?
3. Name one feature in which Z resembled X.
4. Name one feature in which Z resembled Y.
5. Which is the correct evolutionary chain involving X, Y and Z : X → Z → Y or Y → Z → X?

A converging lens of focal length 5cm is placed at a distance of 20cm from a screen. How far from the lens should an object be placed so as to form its real image on the screen?

Give three examples of materials that refract light rays. What happens to the speed of light rays when they enter these materials?

Intake of small quantity of methanol can be lethal. Comment.

The near-point of a person suffering from hypermetropia is at 50cm from his eye. What is the nature and power of the lens needed to correct this defect ? (Assume that the near-point of the normal eye is 25cm).

An element X from group 2 of the periodic table reacts with an element Y from group 17 to form a compound.

1. What is the nature of the compound formed?
2. State whether the compound formed will conduct electricity or not.
3. Give the formula of the compound formed.
4. What is the valency of element X?
5. How many electrons are there in the outermost shell of an atom of element Y?

1. What is meant by periodicity in properties of elements with reference to the periodic table?
2. Why do all the elements of the same group have similar properties?
3. How will the tendency to gain electrons change as we go from left to right across a period? Why?

State the meaning of the term “hot spot” in the context of earth crust. Write one advantage and one limitation of utilizing energy obtained from the hot spots.

(i) Name a metal for each case:
(a) It does not react with cold as well as hot water but reacts with steam.
(b) It does not react with any physical state of water.
(ii) When calcium metal is added to water the gas evolved does not catch fire but the same gas evolved on adding sodium metal to water catches fire. Why is it so?