Force and Laws of Motion — Science STD 9 — Question

How will you separate a mixture of iron filings and powdered carbon?

Explain by an example what is meant by potential energy. Write down the expression for gravitational potential energy of a body of mass m placed at a height h above the surface of the earth.

Why does a desert cooler cool better on a hot, dry day?

The scientists now say that there are actually five states of matter A, B, C, D and E. The state A has a fixed volume but no fixed shape. The state B can be compressed very easily by applying pressure and state C has a fixed shape as well as a fixed volume. The state D is mixture of free electrons and ions whereas state E is named after an Indian scientist and a famous physicist.

1. Name the physical states (i) A (ii) B (iii) C (iv) D, and (v) E.
2. Name one substance belonging to state C which can directly change into vapours on heating. What is this process known as?
3. Name one substance which normally belongs to state B but whose solid form changes directly into gaseous state.
4. Name the most common substance belonging to state A.
5. Which state of matter makes the sum and other stars to glow.

Explain why, osmosis can be considered to be a special kind of diffusion. Classify the following into (i) osmosis, and (ii) diffusion:

1. Swelling up of a raisin on keeping in water.
2. Spreading of virus on sneezing.
3. Earthworm dying on coming in contact with common salt.
4. Shrinking of grapes kept in thick sugar syrup.
5. Preserving of pickles in salt.
6. Spreading of smell of cake being baked in the kitchen.
7. Aquatic animals using oxygen dissolved in water during respiration.