Electricity — Science STD 10 — Question

Give two examples each of the following:

1. Renewable sources of energy.
2. Non-renewable sources of energy.

Give account of chemical properties?Combustion of ethanol.

A student places a candle flame at a distance of about 60 cm from a convex lens of focal length 10 cm and focuses the image of the flame on a screen. After that he gradually moves the flame towards the lens and each time focuses the image on the screen.

1. In which direction-toward or away from the lens, does he move the screen to focus the image?
2. How does the size of the image change?
3. How does the intensity of the image change as the flame moves towards the lens?
4. Approximately for what distance between the flame and the lens, the image formed on the screen is inverted and of the same size?

Write balanced chemical equation with state symbols for the following reaction:
Barium chloride solution reacts with sodium sulphate solution to give insoluble barium sulphate and a solution of sodium chloride.

Why is sustainable management of natural resources necessary? Why is reuse better as compared to recycle?

Which organs in two animals indicate that they are derived from a common ancestor?

What would happen if all the green plants disappear from the earth?

Explain why, when the sun is overhead at noon, it appears white, but when the same sun is near the horizon at sunset, it appears red?

Explain why, natural gas is considered to be a good fuel.

Name the type of reaction for the following:
Burning of natural gas.