A. Answer in Detail:
1. **Question:** How is temperature measured with a thermometer?
**Answer:** Temperature is measured using a thermometer containing a thermometric fluid (e.g., mercury or alcohol) in a sealed glass tube. The fluid expands or contracts with temperature changes, and its level is read against a calibrated scale (Celsius, Fahrenheit, or Kelvin).
2. **Question:** Distinguish between clinical and laboratory thermometers.
**Answer:**
- Clinical Thermometer: Measures human body temperature (35°C–42°C), has a kink to retain readings.
- Laboratory Thermometer: Measures a broader range (-10°C–110°C), no kink, requires manual resetting.
3. **Question:** List the precautions that should be taken while taking temperature.
**Answer:**The precautions are-
Cleaning the thermometer, avoid touching the bulb, waiting for stabilization, avoid exceeding its range, and handle carefully to prevent breakage.
4. **(a) Question:** What do you mean by good and bad conductors of heat? Give examples.
**(a) Answer:**
- Good conductors: Allow heat to flow easily (e.g., copper, aluminum).
- Bad conductors (insulators): Resist heat flow (e.g., wood, plastic).
**(b) Question:** Give two applications each of good and bad conductors of heat.
**(b) Answer:**
- Good conductors: Cooking utensils, radiators.
- Bad conductors: Pan handles, building insulation.
5. **Question:** With the help of an experiment, show convection current in liquids.
**Answer:** First we have to heat a beaker of water with potassium permanganate crystals at the bottom. The colored warm water rises, cools at the top, and sinks, creating a circular convection current. In this way we can show convection current in liquid.
6. **Question:** With the help of an experiment, show conduction of heat in solids.
**Answer:** We attach pins to a metal rod using wax. Heating one end. After that pins fall sequentially as heat conducts through the rod, melting the wax. In this way we can show conduction of heat in solids.
7. **Question:** What are sea breeze and land breeze? Explain.
**Answer:**
- Sea breeze: During daytime, land heats faster than sea. Warm air over land rises and drawing cool air from the sea.
- Land breeze: At nighttime, land cools faster. Warm air over sea rises and pulling cool air from the land.
B. Answer Briefly:
1. **Question:** What is maximum-minimum thermometer?
**Answer:** A thermometer that records the highest and lowest temperatures over a period using two separate scales.
2. **Question:** Why is mercury used as a thermometric fluid?
**Answer:** Mercury expands uniformly, has a high boiling point (357°C), and doesn’t stick to glass.
3. **Question:** What are the different scales of temperature that are used?
**Answer:** Celsius (°C), Fahrenheit (°F), Kelvin (K).
4. **Question:** What are the different modes of heat transfer?
**Answer:** The different modes of heat transfer:
Conduction (solids), convection (liquids/gases), radiation (no medium).
5. **Question:** What do you mean by radiation?
**Answer:** Heat transfer via electromagnetic waves is called radiation.(e.g., sunlight).
6. **Question:** Why do you wear more layers of clothes during winter?
**Answer:** Layers trap air (a poor conductor), improving insulation and keep our body warm during winter.
7. **Question:** Why do Eskimos live in igloos made of snow?
**Answer:**Eskimos live in igloos because snow is an insulator, trapping body heat inside the igloo.
C. Answer in One Word or a Few Words
Fill in the blanks:
1. **Question:** ______ do not require any medium.
**Answer:** Radiation
2. **Question:** Heat transfer by convection takes place in ______ and ______.
**Answer:** liquids, gases
3. **Question:** Dark-coloured objects are good ______ and good ______.
**Answer:** absorbers, emitters
4. **Question:** Temperature of a day is measured with ______ thermometer.
**Answer:** maximum-minimum
5. **Question:** Cooking is faster in ______ vessels.
**Answer:** black/dark-colored
Matching Columns:
1. **Question:** Average body temperature → **Answer:** (iii) 37°C
2. **Question:** Hair and fur of animals → **Answer:** (v) Bad conductors of heat
3. **Question:** Heat from the sun to the earth → **Answer:** (i) Radiation
4. **Question:** Light-coloured clothes → **Answer:** (ii) Summer
5. **Question:** Sea breeze and land breeze → **Answer:** (iv) Convection
MCQ:
1. Question:** Transfer of heat due to convection occurs in
**Answer:** (d) (b) and (c) [liquids and gases].
2. An iron weight at 45 °C is dipped in a bucket containing water at 45 °C. The heat will
**(c) not flow between them.**
3. Conduction can take place when
**(c) both (a) and (b).**
4. Cooking utensils are made up of metals because metals are
**(b) good conductors of heat.**
5. A wooden spoon is used to make vegetable in a metal frying pan. Its other end
**(d) does not become hot.**
6. A thermos flask keeps a liquid hot by preventing heat loss through
**(d) all of these.**
7. The temperature of water can be measured with the help of
**(c) laboratory thermometer.**
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