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प्रश्न
Have you seen someone blowing on their spectacles to wipe them clean? How does the air from the mouth help in cleaning the spectacles?
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उत्तर
The air blown from the mouth is hot and the glass of the spectacles is comparatively colder. The hot air we breathe out contains water vapours which turn into tiny droplets of water when it comes in contact with the colder glass. This makes the glass moist and hazy.
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संबंधित प्रश्न
Miya Balishtiye was confused when he saw the woodcutter blowing on his cold hands to make them warm and on the hot potatoes to cool them.
- Blowhard from your mouth onto your hands. How did you find the air from your mouth as compared to the air around you? Was it hotter, or cooler?
Have you ever burnt your tongue when you ate or drank something that was too hot? How do you cool some food when it is too hot?
If you were to cool these three hot things – dal, roti, rice – in which ways would you do so?
Picture 2 - Sonu was feeling very cold. He kept blowing onto his hands. Now think and write, which will be cooler – Sonu’s hands or his breath?
Make whistles of the things given below. Write in a sequence–from the loudest to the softest whistle.
– Wrapper of a toffee
– A leaf
– A balloon
– The cap of a pen
– Any other thing
Take a glass. Bring it near your mouth and blow hard on it. Do this two or three times. Does the glass look hazy?
Put your hand on your chest. When you breathe in, does your chest come out or go in.
Can you make a mirror hazy in the same way? Can you tell by touching the mirror what made it hazy? Is the air you blew from your mouth dry or wet?
Do you want to listen to your heartbeat? Take a rubber tube as long as the distance from your shoulder to your elbow. At one end of the tube fix a funnel. Place the funnel on the left side of your chest. Put the other end of the tube to your ear. Listen carefully. Did you hear a dhak dhak sound?
Stand with this snake below a fan. Look in which direction it moves. Take this paper snake to different places and observe its movement.
