When a beam of sunlight enters a room throuth 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 doed the existence of this phenomenon give us about the nature of matter ?

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Solution

(a) Dust particles.

(b) Air.

(c) Brownian motion.

(d) The fast moving air molecules are constantly hitting the tiny dust particles causing them to move rapidly in a very haphazard manner.

(e) The gaseous matter ‘air’ is made up of very tiny particles which are constantly moving.

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Q. When extremely small particles X derived from the anther 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 on its surface.
(a) What could particles X be ?
(b) What do you think liquid Y is ?
(c) What is the zig-zag movement of X known as ?
(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 extremely small particles X derived from the anther 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 on its surface.

(a) What could paricles X be ?

(b) What do you think liquid Y is ?

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

(e) Name the scientist who discoverd this phenomenon.

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

Q. (a) What is Brownian motion? Draw a diagram to show the movement of a particle (like a pollen grain during Brownian motion.)
(b) In a beam of sunlight entering a room, we can sometimes see dust particles moving in a haphazard way in the air. Why do these dust particles move?

Three mixtures A, B and C are obtained by stirring three different solids in water taken in separate beakers. When mixture A is allowed to stand for some time, then its particles settle at the bottom of the beaker. When a Beam of light is passed through mixture A in a dark room, the path of light becomes visible when observed from the side of the beaker. When mixture B is allowed to stand for a considerable time, even then its particles do not settle down. Mixture B, however, scatters the beam of light just like mixture A. The particles of mixture C do not settle down on keeping and it also does not scatter a beam of light passing through it

(a) What are the mixtures like A known as ?

(b) What are the mixtures like B known as ?

(d) Name the phenomenon exhibited by A and B which occurs on passing a beam of light through them

(e) Name one mixture each which is like (i) A (ii) B, and (iii) C.

Q. Suspension is a heterogeneous mixture in which very fine particles of a solid are dispersed in any medium (liquid or gas). Fine particles of the solid remain suspended in the medium.

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(a) Dust particles. (b) Air. (c) Brownian motion. (d) The fast moving air molecules are constantly hitting the tiny dust particles causing them to move rapidly in a very haphazard manner. (e) The gaseous matter ‘air’ is made up of very tiny particles which are constantly moving.

(a) Dust particles.

(b) Air.

(c) Brownian motion.

(d) The fast moving air molecules are constantly hitting the tiny dust particles causing them to move rapidly in a very haphazard manner.

(e) The gaseous matter ‘air’ is made up of very tiny particles which are constantly moving.