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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?
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.
- Now put your hands at some distance from your mouth, and blow again. Does the air from your mouth feel warm? Why?
Balishtiye saw that the woodcutter was trying to cool the hot potatoes by blowing on them. What would have happened if he had eaten the potatoes without cooling them?
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?
Picture 1 - Mini tried to cool her tea by blowing on it. Which do you think will be hotter – Mini’s tea or the air she blew from her mouth?
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?
Put your hand on your chest. When you breathe in, does your chest come out or go in.
Put your finger under your nose. Can you feel any air when you breathe out from your nose?
Jump 30 times. Did you feel breathless?
Measure your chest
– Take a deep breath in
– Ask your friend to measure your chest with a thread. Measurement ____________
– Now breathe out. Again ask your friend to measure your chest. Measurement ____________
– Was there any difference in the two measurements of your chest?
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?
