1. Why does a piece of iron get rusted if left exposed in the open ?
Ans : Iron piece rusts is left exposed in the open bcz, it reacts with oxygen in the air, forming iron oxide ---- a compound of iron & oxygen.

2. Why can petrol fire not be put out with water ?
Ans : Petrol is a hydro carbon which remains isolated with water & is having less density. So when water is poured petrol floats on it & keeps on burning.
The temperature of the burning petrol flaots is so high that water poured on the petrol fire is evaporated before it extinguishes the fire.

3. Ice packed is saw dust does not melt quickly. Y ?
Ans : Saw dust is bad conductor of heat & protects the ice from the external heat & hence from melting away quickly.

4. White light passing through a glass prism gives rise to a coloured pattern on the wall. Y ?
Ans : White light is made up of seven colors. Rays of different colors refract / bend along different paths & fall on different points on the wall forming a colored pattern known as spectrum.

5. A boatman pushes the bank with his pole.Y?
Ans : Action & reaction being equal & opposite, the bank will pushes the boat away from it.

6. A burning candle get extinguished when covered with a tumbler.Y?
Ans : A burning candle gets extinguished when covered with a tumbler bcz, the supply of oxygen is cut-off & the flame goes out.

7. Y do u see rainbow after rain ?
Ans : The water drops suspended in the atmosphere act as prism & disperse light into seven colors.

8. A metal tea-pot has an ebony handle.Y?
Ans : Ebony being bad conductor of heat, the handle does not get hot.

9. Y is one's breath visible in winter, but not in summer?
Ans : In winter the water vapour contained in the breath condenses into smaller droplets of water, which bcm visible. In summer it is not so.

10. The weight of a man on the surface of the moon will be only about one-sixth of his weight on the earth.Y?
Ans : The gravity of the moon is one-sixth that of the earth.so only it is so.

11. Y is it easier to roll a barrel than to pull it along the road?
Ans : Slipping resistence is much more than rolling resistence.

12. Y is the flash of lightning seen before teh sound of thunder is heard?
Ans : because , light travels faster than sound.

13. How does a soda water straw work?
Ans : When we suck through soda water straw, low pressure is created inside the straw. The liquid outside rushes in to balance the difference.

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