NCERT CLASS 7 SCIENCE CHAPTER 4 HEAT
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NCERT CLASS 7 SCIENCE CHAPTER 4 HEAT
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NCERT CLASS 7 SCIENCE CHAPTER 4 HEAT
Question Answers
Q. 1. Boojho says, “My left hand tells me that the water in mug C is hot and the right hand tells me that the the same water is cold. What should I conclude”? (Page 36)
Ans. Both of the conclusions are true relative to each hand, but a single conclusion can not be drawn from the given information.
Q. 2 Boojho wondered which of the two scales shown in Fig. he should read. Paheli told him that India has adopted the Celsius scale and we should read that scale. The other scale with the range 94-108 degrees is the Fahrenheit scale (°F).It was in use earlier. (Page 36)
Fig. A Clinical Thermometer.
Ans. Yes.
Q.3 Boojho got a naughty idea.He wanted to measure the temperature of hot milk using a Clinical Thermometer. Paheli stopped him from doing so. Why? (Page 38)
Ans. Yes, do not use a Clinical Thermometer for measuring the temperature of any object other than the human body because it may break.
Q.4 Boojho now understand why clinical thermometer cannot be used to measure high temperatures. But still wonders whether a laboratory thermometer can be used to measure his body temperature. (Page 39)
Ans. Yes, laboratory thermometer can also be used for measuring body temperature.
Q.5. Boojho wonders why the level of mercury should change at all when the bulb of the thermometer is brought in contact with another object? (Page 39)
Ans. The temperature of other object may not be the same as that of the bulb of the thermometer. When bulb is brought in contact with that object, the temperature of the bulb changes. Thus, the level of mercury also changes.
Q.6 Paheli asks: “Does it mean that heat will not be transferred if the temperature of two objects is the same?”. (Page 40)
Ans. Yes.
NCERT TEXTBOOK EXERCISE
Q.1 State similarities and differences between the laboratory thermometer and the clinical thermometer.
Ans. Similarities: (i) Both use mercury.
(ii) Both measure temperature.
Differences: (i)The range of a Mercury thermometer is 100°C. A Mercury thermometer having graduations from 0°C to 100°C while the temperature interval marked on the clinical thermometers ranges from 35°C to 43°C.
(ii)The temperature on laboratory thermometer falls by itself, but not so in clinical thermometer. In clinical thermometers , a jerk is given so that it is set again for measuring human body temperature.
Q 2 Give two examples each of conductors and insulators of heat.
Ans. Conductors: Copper, Aluminum.
Insulators: Wood, plastic.
Q.3 Fill in the blanks :
(a) The hotness of an object is determined by its ……
(b) Temperature of boiling water cannot be measured by a ……. thermometer.
(c) Temperature is measured in degree…….
(d)No medium is required for transfer of heat by the process of ……….
(e) A cold steel spoon is dipped in a cup of hot milk. It transfers heat to it’s other end by the process of ……..
(f) Clothes of …….colours absorbs heat better than clothes of light colours.
Ans. (a) Temperature (b) Clinical (c) Celsius (d) Radiation (e) Conduction (f) Dark/black.
Q.4 Match the following:
| Column I | Column II |
| (i) Land breeze blows during | (a) summer |
| (ii) Sea breeze blows during | (b) winter |
| (iii) Dark coloured clothes are preferred during | (c) day |
| (iv) Light coloured clothes are preferred during | (d) night |
Ans. (i) (d) ;(ii) (c) ;(iii) (b) ;(iv) (a).
Q.5 Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.
Ans. More layers of clothing keep us warm in winter’s as they have a lot of space between them. Air is a poor conductor of heat. This increases the insulation and thus , comfortability warm the clothes as a whole.
Q.6 Look at a figure below mark where the heat is being transferred by Conduction, by convection and by radiation
Fig.
Ans. Fig.
Q.7. In places of hot climate, it is advised that the outer walls of houses be painted white. Explain.
Ans. In places of hot climates , it is advised that the outer walls of house be painted white, because white colour do not radiate heat easily.
Q 8 One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be:
(a) 80°C (b) more than 50°C but less than 80°C
(c) 20°C. (d) between 30°C and 50°C.
Ans.(d) between 30°C and 50°C.
Q.9. An iron ball at 40°C is dropped in a mug containing water at 40°C.The heat will:
(a) flows from iron ball of water.
(b) not flow from iron ball to water or from water to iron ball.
(c) flow from water to iron ball.
(d) increase the temperature of both.
Ans. (b) not flow from iron ball to water or from water to iron ball.
Q.10. A wooden spoon is dipped in a cup of ice cream.Its other end:
(a) becomes cold by the process of Conduction.
(b)becomes cold by the process of convection.
(c) becomes cold by the process of radiation.
(d) does not become cold.
Ans. (d) does not become cold.
Q.11 Stainless steel pans are usually provided with copper bottoms. The reason for this could be that:
(a) copper bottom makes the pan more durable (b) such pans appear colourful
(c) copper is a better conductor of heat than the Stainless steel
(d) copper is easier to clean than the Stainless steel.
Ans. (c) copper is a better conductor of heat than the Stainless steel.
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Class 7 Science
- Chapter 1. Nutrition in Plants
- Chapter 2. Nutrition in Animals
- Chapter 3. Fibre to Fabric
- Chapter 4. Heat
- Chapter 5. Acitds, Bases and Salts
- Chapter 6. Physical and Chemical Changes
- Chapter 7. Weather; Climate and Adaptations of Animals to Climate
- Chapter 8. Winds, Storms and Cyclones
- Chapter 9. Soil
- Chapter 10. Respiration in Organisms
- Chapter 11. Transportation in Animals and Plants
- Chapter 12. Reproduction in Plants
- Chapter 13. Motion and Time
- Chapter 14. Electric Current and its Effects
- Chapter 15. Light
- Chapter 16. Water; a Precious Resource
- Chapter 17. Forests; Our Lifeline
- Chapter 18. Wastewater Story