An inflated balloon full of air goes down slowly (becomes smaller and smallers lowly) even though the knot at the mouth of the balloon is air tight. And after a week all the air has escaped from the balloon. Explain how the air particles got out of the balloon.

Explain why, osmosis can be considered to be a special kind of diffusion. Classify the following into

(i) osmosis, and (ii) diffusion:

(a) swelling up of a raisin on keeping in water

(b) spreading of virus on sneezing

(c) earthworm dying on coming in contact with common salt

(d) shrinking of grapes kept in thick sugar syrup

(e) preserving of pickles in salt

(f) spreading of smell of cake being baked in the kitchen

(g) aquatic animals using oxygen dissolved in water during respiration

A student placed a gas jar containing air in the upside down position over a gas jar full of red-brown bromine vapours. He observed that the red brown colour spread upwards into the jar containing air. Based on this observation, the student concluded that it is only the bromine vapour which moves up and diffuses into air in the upper jar, the air from the upper jar does not move down by diffusion into the lower jar containing bromine vapours. Do you agree with this conclusion of the student? Give reason for your answer.

When extremely small particles X derived from the another of a flower were suspended in a liquid Y and observed through a microscope, it was found that the particles X were moving throughout the liquid Y in a very zig zag way. It was also observed that warmer the liquid Y, faster the particles X moved in its surface.

(a) What could particles X be?

(b) What do you think liquid Y is?

(c) What is the zig-zag movement of particles X?

(d) What is causing the zig-zag movement of particles X?

(e) Name the scientist who discovered this phenomenon.

(f) What does this experiment tell us about the nature of liquid Y?

When a beam of sunlight enters a room through a window, we can see tiny particles X suspended in a gas (or rather a mixture of gases) Y which are moving rapidly in a very haphazard manner.

(a) What could particles X be?

(b) Name the gas (or mixture of gases) Y.

(c) What is the phenomenon exhibited by particles X known as?

(d) What is causing the movement of particles X?

(e) What conclusion does the existence of this phenomenon give us about the nature of matter?