Nature's Treasures — Science STD 6 — Question

Give two examples each for linear, circular and oscillatory motion.

We know that water changes into vapour when heated. But it is a common experience that water from wet roads, rooftops and floors disappears without heating. Explain how water changes into its vapour even without heating?

What are nodes and internodes?

Activity.

1. Make a mixture of dry sand with sawdust or powdered dry leaves. Keep this mixture on a plate or a newspaper. Look at this mixture carefully.

Can the two different components be made out easily? Are the sizes of particles of the two; components similar? Would it be possible to separate the components by handpicking?

2. Now, take your mixture to an open ground and stand on a raised platform. Put the mixture in a plate or sheet of paper. Hold the plate or the sheet of paper containing the mixture, at your shoulder height. Tilt it slightly, so that the mixture slides out slowly.

What happens? Do both the components– sand and sawdust (or powdered leaves) fall at the same place? Is there a component that blows away? Did the wind manage to separate the two components?

What are the different ways by which water vapour is put into the atmosphere?

Why all the oxygen of atmosphere does not get used up though a large number of organisms are consuming it?

What is balanced diet?

Draw a labelled diagram of the external structure of a leaf.

Why primitive life was confined to the tropics? When was it possible for the people to migrate to colder regions?

Write the differences between umbra and penumbra.