Question1. Choose the correct option.
- Temperature is measured in.
(i)Calorie (ii) erg (iii)Joule (iv) Degree Celsius
Answer. (iv) Degree Celsius
- Which of the following is true for Breeze?
(i)Cool air flows from the sea towards the land.
(ii) Hot air flows from the sea towards the land
(iii) Hot air flows from land towards the sea
(iv) Cool air flows from land towards the sea.
Answer. (i)Cool air flows from the sea towards the land.
C. Which type of thermometer is used to measure the temperature of chemicals with high accuracy?
(i)Clinical thermometer (ii) Laboratory thermometer (iii)Digital thermometer (iv) Six’sthermometer
Answer. (ii) Laboratory thermometer
D. The surface of an object is given a darker color because it is a:
(i)bad conductor of heat (ii) good reflector of heat(iii)bad emitter of heat (iv) good absorber of heat
Answer. (iv) good absorber of heat
Question2. Assertion – Reasoning Questions.
In the following questions, two statements are given one labeled as Assertion (A) and the other labeled as Reason (R)
Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
- Both Assertion (A) and Reason are (R) are true and reason ( R) is the correct explanation of the Assertation (A )
- Both Assertion (A) and Reason are (R) are true and reason (R) is not the correct explanation of the Assertation (A)
- Assertion (A) is true, but reason (R) is false
- Assertion (A) is false, but reason (R) is true
- Assertation (A): When an iron rod at 50 ° c is brought in contact with water at 30° c, heat flows from the iron rod to water.
Reason (R): Heat always flows from a body at a higher temperature to a body at a lower temperature.
- Assertation (A): We wear dark coloured clothes during winter.
Reason (R) Dark-coloured clothes are poor absorbers of heat.
(i) Assertion (A): When an iron rod at 50 °C is brought in contact with water at 30°C, heat flows from the iron rod to water.
Reason (R): Heat always flows from a body at a higher temperature to a body at a lower temperature.
Explanation:
Both Assertion (A) and Reason (R) are true. Assertion (A) is true because heat indeed flows from a higher temperature body to a lower temperature body, as stated in Reason (R). Therefore, the correct answer is (a).
(ii) Assertion (A): We wear dark-colored clothes during winter.
Reason (R): Dark-colored clothes are poor absorbers of heat.
Explanation:
Assertion (A) is false because we wear dark-colored clothes during winter precisely because they are good absorbers of heat. So, Assertion (A) contradicts Reason (R). Therefore, the correct answer is (c).
Question 3. Answer the following questions in one sentence.
- What is the function of a thermos flask?
Answer. The function of a thermos flask is to, maintain the temperature of its contents by minimizing heat transfer through conduction, convection, and radiation.
- What is the process by which heat can travel in a vacuum?
Answer. Heat can travel in a vacuum through radiation.
- Convert – 26 °C into kelvin.
Answer. -26 °C is equivalent to 247 K.
- What is the freezing point of mercury?
Answer. The freezing point of mercury is -38.83°C or 234.32 K.
Question4. Answer the following questions in 2 – 3 sentences.
- What are three units used for the measurement of temperature?
Answer.The three units used for the measurement of temperature are Celsius (°C), Fahrenheit (°F), and Kelvin (K).
- The temperature of Mumbai city was recorded as 45°C. What would be the temperature of Mumbai city in Fahrenheit?
Answer. The temperature of Mumbai city in Fahrenheit would be 113°F.
- Define heat and state the SI unit of heat.
Answer. Heat is the energy transferred between substances due to a temperature difference. The SI unit of heat is the joule (J).
- People wear light coloured clothes in summer. Give reasons.
Answer.People wear light-colored clothes in summer because light colors reflect sunlight, reducing the absorption of heat and helping to keep the body cooler.
Question5.Answer the following questions in 3 – 4 sentences.
- What are the precautions, one must take while using a clinical thermometer?
Answer. When using a clinical thermometer, it’s important to, ensure that the thermometer is clean before and after each use to prevent the spread of infections. Additionally, it should be inserted into the mouth, armpit, or rectum for the required amount of time, following the manufacturer’s instructions carefully. After use, it should be sanitized properly.
- What are the conductors of heat? Give two examples.
Answer. Conductors of heat are materials that allow heat to flow through them easily. Metals such as copper and aluminum are good conductors of heat. For example, copper is commonly used in electrical wiring due to its high thermal conductivity, while aluminum is used in cookware for its ability to quickly distribute heat.
(c)State any two differences between conduction, convection, and radiation.
Answer. Conduction, convection, and radiation are three mechanisms of heat transfer. Conduction involves the transfer of heat through direct contact between particles of matter. Convection occurs through the movement of fluids (liquids or gases) due to temperature differences, resulting in heat transfer. Radiation involves the emission of electromagnetic waves that carry heat energy and can transfer heat through empty space.