NCERT Solutions Class 5 EVS Chapter 15 – Blow Hot, Blow Cold explain the meaning of warmth and cold. NCERT books are preferred both by teachers and students. Class 5 is the phase in a student’s life, where they start learning and exploring new things. Chapter 15 ‘Blow Hot, Blow Cold’ is an interesting chapter. These NCERT Solutions help students to learn the difference between warmth and cold. Also, they help them to think and imagine in their own ways. Imagining in their own method helps the students to become rational intellects.
This is a short summary of the book NCERT Class 5 EVS Chapter 15. To learn more about the chapter, refer to the solutions given below.
Access NCERT Solutions for Class 5 EVS Chapter 15 Blow Hot, Blow Cold
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.
Q1. Have you warmed your hands in winter by blowing on them when they are cold? How does it feel?
Answer: Yes, blowing on my hands made my hands warmer in winter. It feels warmer and more comfortable.
Q2. Blow hard 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?
Answer: Blowing hard from my mouth onto my hands, the air from the mouth was hotter than the outside air around me.
Q3. Now put your hands at some distance from your mouth, and blow again. Does the air from your mouth feel warm? Why?
Answer: When we put our hands at some distance from our mouth and blow the air from the mouth, we feel that the air is not warmer. Since the hand is kept far at a place, by the time the air blown from the mouth reaches the hand, it becomes cold by mixing with the air around.
Think and tell
Q1. Can you think of any other way in which you use the warmth from your breath?
Answer: We can use the warmth of the breath for the redness of the eye or any injury by blowing it onto the handkerchief, and keeping it on the redness of the eye gives relief.
Q2. Fold a piece of cloth 3-4 times. Now bring it close to your mouth and blow hard on it. Did the cloth become warm?
Answer: Yes, even after folding the cloth 3-4 times and by blowing the air from the mouth, the cloth results in warmth.
Q3. 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?
Answer: If Balishtiye had eaten the hot potatoes without cooling them, then it would have caused burns in his mouth.
Q4. 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?
Answer: Yes, while sipping hot tea, I burnt my tongue. I sometimes use a fan to cool my food or otherwise, by blowing over it, I cool it.
Q5. If you were to cool these three hot things – dal, roti, rice – in which ways would you do so?
Answer: To cool down these items, first, we should keep them in a wider container and keep them under a fan, or if they are in less quantity, we can blow over them and cool them.
Q6. For what other things do you blow air from your mouth?
Answer: We blow air from our mouths to clean spectacles, whistle, clean any dust particles, blow the flute, etc.
Q1. 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?
Answer: Mini’s tea will be hotter than the air that she blew from her mouth.
Q1. Sonu was feeling very cold. He kept blowing on to his hands. Now think and write, which will be cooler – Sonu’s hands or his breath?
Answer: Sonu’s hands will be cooler. Since his hands are open to the air outside, it makes his hands colder.
Blow in different ways
Q1. 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
Answer: The sequence from the loudest to the softest whistle is given below.
– The cap of the pen
– By putting fingers in the mouth
– By wrapping a toffee
– By a balloon
– By a leaf
Q2. Have you seen people playing different musical instruments like flute, dholak, been, guitar, mridang, etc.? Can you recognise their sounds with your eyes closed? Find out more about these musical instruments. Collect their pictures too.
Answer: Yes, by closing my eyes, I can recognise the sounds of flute, dholak, been, guitar, mridang, etc.
Flute: It is one of the musical instruments into which we blow air to play. Hence, it is a wind instrument.
Dholak: It is a two-headed hand drum from the Indian subcontinent. It is basically a folk instrument. Hence, it is a type of percussion instrument.
Guitar: It is a type of sting instrument consisting of strings in it.
Been: It is also a type of wind instrument. It is played by blowing the air from the mouth.
Mridang: It is a double-sided drum whose body is usually made using a hollowed piece of jackfruit wood. It is a type of percussion instrument.
Q1. Can you name some things which produce melodious or pleasing sounds when we blow into them?
Answer: Here are a few musical instruments which produce melodious or pleasing sounds when we blow air into them: flute, mouth organ, been, banjo, etc.
Do this and discuss
Q1. Have you seen someone blowing on their spectacles to wipe them clean? How does the air from the mouth help in cleaning the spectacles?
Answer: Yes, I have seen some people blowing air on to the spectacles to clean them. The moisture from the air blown gets converted into droplets of water on the glass and, hence, can clean the spectacles.
Q2. Take a glass. Bring it near your mouth and blow hard on it. Do this two or three times. Does the glass look hazy?
Answer: Yes, by blowing air into the glass, the moisture formed by the air blown comes in contact with the glass, which makes the glass look hazy. It’s not just the glass even the mirror also becomes hazy when air is blown onto it.
Q3. 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?
Answer: Yes, I can make the mirror hazy as well. When we blow the air, the moisture formed by the air blown comes in contact with the mirror, which makes the mirror look hazy. The air blowing from the mouth is wet.
Q4. Put your hand on your chest. When you breathe in, does your chest come out or go in?
Answer: By putting hands on the chest when we breathe in, the chest comes out.
Q5. 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?
Answer: The measurement of the chest when I took a deep breath in is 25cm.
The measurement of the chest when I breathe out is 21cm.
Yes, there was a difference between the two measurements; when we breathe in, the chest comes out and measures more. While we breathe out, the chest goes in and measures less.
How many breaths in one minute
Q1. Put your finger under your nose. Can you feel any air when you breathe out from your nose?
Answer: When I put my figure under my nose, I can feel the air that we breathe out.
Q2. Count how many times in one minute you breathe in and breathe out.
Answer: Around 16-18 times per minute, I breathe in and breathe out.
Q3. Jump 30 times. Did you feel breathless?
Answer: Yes, by jumping 30 times, I felt breathless.
Q4. Now again, count how many times in one minute you breathed in and out.
Answer: So, after jumping, I breathed in and out around 25 times per minute.
Q5. What was the difference in your count before and after jumping?
Answer: The difference in the count before and after jumping is 7 counts since the rate of breathing increases due to jumping.
The clock inside you
Q1. You have all heard the ‘tick tick’ of the clock. Have you seen a doctor using a stethoscope to listen to your chest? What do you think she hears? Where is the sound coming from? Is there a clock inside your chest that keeps ticking away?
Answer: Yes, I have seen doctors using a stethoscope to listen to our chest. They hear the heartbeat. The sound of the heartbeat comes from the heart while it pumps blood to the other parts of the body. No, it’s not a clock to keep ticking away; it’s the heart which is beating.
Q2. 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?
Answer: Yes, I could hear the sound.
Snake tells the flow of air!
Q1. Stand with this snake below a fan. Look in which direction it moves. Take this paper snake to different places and observe its movement.
Answer: When we take the paper snake under a fan, it rotates in an anticlockwise direction since the air moves downwards.
Q7. Can you understand from the movement of the snake – if the air is moving upwards or downwards?
Answer: Yes, we can understand from the movement of the snake whether the air is moving upwards or downwards. If the paper snake moves in a clockwise direction, then we can say that the air is moving upwards.
If the paper snake moves in an anticlockwise direction, then we can say that the air is moving downwards.
What we have learnt
Q1. While playing, Amit hit a wall. His forehead was swollen. Didi immediately folded a scarf (4-5 times), blew on it and kept it on Amit’s forehead. Why do you think didi did this?
Answer: Didi, by doing so, could reduce the swollen area. Pressing a kerchief blown with air on the injury gives relief and reduces pain.
Q2. We blow to cool hot things as well as to warm them. Give examples of each.
Answer: To cool hot things like a hot cup of tea, a bowl of hot food, etc., we blow air to cool.
For things which are colder, like a piece of cloth, hands can be warmed up by blowing air.