Chapter 4: Heat
Question 1: State the similarities and differences between a clinical thermometer and a laboratory thermometer.Answer: Similarities between the laboratory thermometer and the clinical thermometer
- Laboratory thermometer and the clinical thermometer thermometers consist of long narrow uniform glass tubes.
- Laboratory thermometer and the clinical thermometer have a bulb at one end.
- Laboratory thermometer and the clinical thermometer contain mercury in the bulb.
- Laboratory thermometer and the clinical thermometer use Celsius scale on the glass tube.
Differences between the laboratory thermometer and the clinical thermometer:A clinical thermometer reads temperature 35°C to 45°C while the range of laboratory thermometer is -10°C to 110°C.The clinical thermometer has a kink near the bulb while there is no kink in the laboratory thermometer. Due to kink, mercury does not fall down on its own in clinical thermometer.
Question2: Give two examples each of insulators and conductors of heat.Answer: - Conductors – silver, copper
- Insulators – rubber, plastic.
Question3:Complete the sentence with appropriate answers: - ____________ can determine an object’s hotness.
- ___________ Thermometer cannot be used to measure the temperature present in boiling water.
- __________ Degree is used to measure temperature.
- ___________ requires no medium for heat transfer for the process.
- An ice-cold steel fork is dipped into a mug of hot water. The transfer of heat to the other end is by the process of ___________.
- ____________ Color clothes absorb heat better than clothes of light colors.
Answers: - Temperaturecan determine the object hotness.
- ClinicalThermometer cannot be used to measure the temperature of boiling water.
- CelsiusDegree is used to measure temperature.
- Radiation requires no medium for heat transfer for the process
- An ice-cold steel fork is dipped into a mug of hot water. Transfer of heat to the other end is by the process of
- Dark Color clothes absorb heat better than clothes of light colors.
Question 4:Match the following:1. Land breeze blows during | (a) day |
2. Sea breeze blows during | (b) summer |
3. Dark colored clothes are preferred during | (c) night |
4. Light colored clothes are preferred during | (d) winter |
Answers:1. Land breeze blows during | (c) night |
2. Sea breeze blows during | (a) day |
3. Dark colored clothes are preferred during | (d) winter |
4. Light colored clothes are preferred during | (b) summer |
Question5: Wearing more layers of clothes during winter keeps us warmer than wearing only one thick piece of clothing. Discuss why.Answer: More layers of clothing actually keep us warmer in winters as they have a lot of space between them. That space gets filled up with air. Air is a bad conductor; it does not allow the body heat to escape out.
Question6: Mark the places in which the heat is being transferred by convection, conduction and by radiation.Answer: Question7: Explain why buildings in the places that have hotter climate are advised to paint the outer walls white.Answer: Since the white color reflects heat, it helps the house to not get heated up so much.
Question8: When a liter of water at 50°C is mixed with another liter of water at 30°C what will be the temperature of the mixture?(1)80°C (2) lesser than 80°C but greater than 50°C(3) 20°C (4) Between 50°C and 30°C
Answer: (4)Between 50°C and 30°C
Question9: In a mug that contains water at 40°C, an iron ball which is 40°C is dropped. Mention the flow of heat: - Flow from the iron ball to water.
- Will not flow from water to iron ball or from iron ball to water.
- Will flow from the water to the iron ball.
- Both the temperatures increase.
Answer: (2) Will not flow from water to iron ball or from iron ball to water.
Question10: A wooden fork is dipped in a bowl of ice-cold water and its other end: - Becomes cold due to the process of convection
- becomes cold due to the process of radiation
- becomes cold due to the process of conduction
- Doesn’t become cold.
Answer: (4) Doesn’t become cold.
Question 11: Why stainless steel pans that we use at home is are provided with copper bottoms? The reason might be: - Such type of pans appear to be colorful
- Copper is a much better conductor of heat than that of stainless steel.
- Copper is much easier to clean after use when compared to that stainless steel
- Copper bottoms in pans are more durable.
Answer:(2) Copper is a much better conductor of heat than that of stainless steel.