CBSE Class 5 EVS NCERT Solutions: Chapter 15 Blow Hot, Blow Cold
This chapter, 'Blow Hot, Blow Cold', from CBSE Class 5 EVS, explores the fascinating concept of using the warmth of our breath. Through engaging questions, students will investigate how blowing on their hands can make them warmer and how the same breath can be used to cool hot food, like potatoes or tea. The solutions encourage practical observation and personal experience, prompting students to think about everyday situations where they utilize their breath's temperature. This chapter helps young learners understand the basic principles of heat transfer and how our bodies naturally regulate temperature. These NCERT solutions are designed to aid students in understanding these concepts, reinforcing their learning through relatable examples, and preparing them for assessments by clarifying the practical applications of scientific principles in daily life.
Quick info
| Board | CBSE |
|---|---|
| Class | Class 5 |
| Subject | EVS |
| Session | 2026 |
| Language | English |
| Type | NCERT Solutions |
| Chapter | Chapter 15 |
Chapter summary
Chapter 15, 'Blow Hot, Blow Cold', for CBSE Class 5 EVS focuses on the dual nature of breath: its ability to warm and cool. The exercises prompt students to experiment with blowing on their hands to feel the warmth and on hot food to cool it down. It encourages them to relate these actions to real-life scenarios, such as a woodcutter warming his hands or cooling potatoes. The chapter aims to build observational skills and a basic understanding of heat transfer through personal experience.
Learning outcomes
- Understand that breath can be both warm and cool.
- Experiment with blowing on hands to feel warmth.
- Observe how blowing can cool hot objects.
- Relate personal experiences of warming and cooling with breath.
- Identify everyday situations where breath is used for temperature regulation.
Topics covered
Paper topics
- Warmth of breath
- Cooling effect of breath
- Heat transfer
- Temperature regulation
- Everyday science
- Observation skills
- Practical application of breath
Important topics
- Using breath to warm hands
- Using breath to cool hot food
- Understanding heat transfer through blowing
- Relating breath temperature to need
PDF preview
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Questions and Solutions
Question Do This:
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.
Have you warmed your hands in winter by blowing on them when they are cold? How does it feel?
- Blow hard from your mouth onto your hands. How did you find the air from your mouth as compared to the air around? Was it hotter, or cooler?
Now put your hands at some distance from your mouth, and blow again. Does the air from your mouth feel warm? Why?
Yes, I have warmed my hands in winter by blowing on them when they are cold. It feels pleasant and soothing as the warmth spreads through my fingers.
When I blow hard from my mouth onto my hands, the air feels warmer compared to the surrounding air. This is because the air coming from my lungs is at a higher temperature than the ambient air.
When I put my hands at some distance from my mouth and blow again, the air from my mouth still feels warm. This is because the air I exhale is heated by my body's internal temperature before it leaves my mouth.
Question Think and Tell:
Can you think of any other way in which you use the warmth from your breath?
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?
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?
If you were to cool these three hot things - dal, roti, rice - in which ways would you do so?
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?
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?
For what other things do you blow air from your mouth?
Yes, I can think of other ways I use the warmth from my breath. For example, I might blow on my hands to warm them up if they are cold, or I might blow on a cold windowpane to see through it better as the warmth helps to clear the condensation.
Yes, when I fold a piece of cloth 3-4 times and blow hard on it, the cloth does become warm. This is because the warm air from my breath transfers heat to the fabric.
If the woodcutter had eaten the potatoes without cooling them, he would have likely burnt his tongue and the inside of his mouth. Eating food that is too hot can cause pain and injury.
Yes, I have burnt my tongue before when eating something too hot. To cool hot food, I usually blow on it gently. Sometimes, I might also stir it or let it sit for a while to allow it to cool down naturally.
To cool hot dal, roti, or rice, I would use a combination of methods. For dal, I might stir it vigorously with a spoon to help release heat, or I could pour it into a wider, shallower bowl. For roti, I might fan it or gently blow on it. For rice, I could spread it out on a plate or fan it.
Mini's tea will be hotter than the air she blew from her mouth. The air she exhales is warm, but the tea is significantly hotter, which is why she is trying to cool it down.
Sonu's breath will be cooler than his hands. His hands are cold because the surrounding air has taken away their heat. His breath, being warm air from inside his body, is warmer than the cold air and his cold hands.
I blow air from my mouth for several other things. For example, I blow on a hot cup of soup or noodles to cool them before eating. I also blow on a musical instrument like a flute or a harmonica to produce sound. Sometimes, I might blow on a candle to extinguish it, or blow bubbles with soap water.
Common mistakes
- Confusing the direction of heat transfer (warmth from breath vs. cooling effect).
- Not realizing that the temperature of the breath changes based on the need (warming hands vs. cooling food).
- Failing to connect personal actions with the scientific principle of heat transfer.
Revision tips
- Perform the experiments described in the chapter (blowing on hands, blowing on cloth) to feel the difference.
- Think of at least three different situations where you have used your breath to change the temperature of something.
- Discuss with friends or family how they use their breath to warm or cool things.
- Draw pictures illustrating the woodcutter warming his hands and cooling potatoes.
Practice MCQs
Q1. When you blow on your cold hands, what do you feel?
Explanation: When you blow on your cold hands, the warm air from your lungs transfers heat to your hands, making them feel warmer.
Q2. Why does blowing on hot food help to cool it down?
Explanation: The air blown from your mouth, even if it's warm, is moving. This movement helps to increase the rate of heat loss from the hot food's surface, thus cooling it down.
Q3. What did Miya Balishtiye observe the woodcutter doing?
Explanation: The woodcutter was blowing on his cold hands to warm them and on hot potatoes to cool them, demonstrating the dual use of breath.
Q4. If you eat very hot potatoes without cooling them, what might happen?
Explanation: Eating food that is too hot can cause burns to the sensitive tissues in your mouth and on your tongue.
Q5. When you blow on a folded piece of cloth, what do you notice?
Explanation: Blowing on the cloth transfers the warmth from your breath to it, making the cloth feel warmer.
Frequently asked questions
What is the main concept of CBSE Class 5 EVS Chapter 15?
The main concept is understanding that our breath can be used to either warm things (like our hands) or cool things (like hot food), depending on how we use it.
Why does blowing on cold hands make them warmer?
When you blow on your cold hands, the warm air from your lungs comes into contact with your skin, transferring heat and making your hands feel warmer.
How does blowing on hot food help to cool it?
The air you blow, even if it's warm, is moving. This airflow helps to carry away the heat from the surface of the hot food, thus cooling it down faster.
Can a student answer the questions in this chapter?
Yes, many questions in this chapter are designed for students to answer based on their personal experiences and observations, encouraging hands-on learning.
How do these NCERT solutions help students?
These solutions provide clear explanations and guidance for the practical activities and thought-provoking questions in the chapter, helping students grasp the concepts of heat and temperature.
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