1. Heat is a form of energy that gives us the sensation of warmth. Heat always flows from a hot body to a cold body.
  2. Temperature is the measure of the hotness or coldness of a body.
  3. This is a blog containing all the questions and answers, solutions, solved exercises, solved numerical problems, and an answer guide for Secondary Education Examination (SEE) appearing students of Nepal from Heat chapter of class 10.
  4. Questions have been derived from Oasis School Science Grade 10 book. 

Unit - 4 | Heat | Questions and Answers



Before we start seeing the questions, answers, solutions, and solved exercises of the heat chapter for class 10 students of Nepal. Here is a note that we have prepared for you that you must check before seeing this answer guide.
Notes

Very Short Answer Questions

These types of questions in Science carry 1 mark each and are typical of one sentence.


1. Define heat. Write its SI unit.
Answer: Heat is defined as the sum total of kinetic energy contained by the molecules of a body.
Its SI unit is Joule (J).


2. State the factors on which the amount of heat present in a body depends.
Answer: The amount of heat present in a body depends on the following factors:
a) average KE of molecules and b) mass of the body

3. Define heat energy on the basis of molecular kinetic theory.
Answer: On the basis of molecular kinetic theory, heat energy can be defined as the sum total of kinetic energy contained by the molecules of a body.

4. Define one calorie of heat energy.
Answer: One calorie of heat energy can be defined as the amount of heat energy required to raise the temperature of 1 gram pure water by 1°C, or 1°F.

5. Define one joule of heat energy.
Answer: One joule of heat energy can be defined as the amount of heat energy required to raise the temperature of 1-kilogram pure water by 1°C, or 1°F.

6. Define temperature and write down its SI unit.
Answer: Temperature is defined as the measure of hotness or coldness of a body.
Its SI unit is Kelvin (K).

7. Write down the formula and SI unit of specific heat capacity.
Answer: The formula of specific heat capacity is:
$s = \dfrac{Q}{mdt}$.
Its SI unit is J/kg°C.

8. Which principle is the construction of a thermometer based on?
Answer: The construction of a thermometer is based on the principle of "Liquid expands on heating and contracts on cooling".

9. Name any two liquids which are used in the thermometer.
Answer: Any two liquids which are used in the thermometer are: a) Alcohol and b) Mercury.

10. Write down the boiling and melting points of mercury in normal pressure.
Answer: In normal pressure, the boiling point of mercury is 357°C and the melting point is -39°C.

11. What is a clinical thermometer?
Answer: A clinical thermometer is a medical thermometer that is used to measure the temperature of human beings and animals.

12. Why is a clinical thermometer used?
Answer: Clinical thermometer is used to measure human and animal body temperature.

13. What is a digital thermometer?
Answer: A digital thermometer is a modern thermometer that shows the temperature in digits.

14. What is a maximum-minimum thermometer?
Answer: A maximum-minimum thermometer is a type of thermometer that is used to measure the maximum and minimum atmospheric temperature of 24 hours of a particular place.

15. Name the instrument which is made on the basis of expansion of a liquid on heating.
Answer: The instrument made on the basis of expansion of liquid on heating is the thermometer.

16. What is the body temperature of a healthy human?
Answer: The body temperature of a healthy human is 98.6°F or 37°C.

17. Write two factors that affect heat energy.
Answer: The two factors that affect heat energy are:
a) Kinetic Energy of the molecules contained in the body
b) Mass of the body

18. What is the boiling point of water in the Kelvin unit?
Answer: The boiling point of water in the Kelvin unit is 373.2 K.

19. Write down the formula of the heat equation.
Answer: The formula of the heat equation is: Q = msdt.

20. What is meant by 1 calorie heat?
Answer: 1 calorie heat means that 1 joule of heat energy is used to raise the temperature of pure water by 1°C or 1 K.

21. What is the value of the specific heat capacity of water?
Answer: The value of the specific heat capacity of water is 4200 J/kg°C.

22. What is the relation between the specific heat capacity and the rate of increase or decrease in its temperature?
Answer: The relation between the specific heat capacity and the rate of increase or decrease in its temperature is:
$specific \;heat\; capacity \propto \dfrac{1}{rate\; of \;increase\; or\; decrease \;in\; temperature}$


Short Answer Questions

These types of questions in Science carry 2 marks each and are generally differences between, reasoning, functions, uses, or a combination of two questions from very short answer questions.

1. What is the relation among the amount of heat energy contained by a body, its mass and kinetic energy of the molecules?
Answer: Let us denote amount of heat energy contained by 'Q', its mass as 'm' and kinetic energy of the molecules as 'KE'. Their relation can be written as:
Q $\propto$ KE × m

2. Write any two differences between heat and temperature.
Answer: Any two differences between heat and temperature is given below:
Heat Temperature
Heat is the sum total of kinetic energy contained by the molecules of a body. Temperature is the average kinetic eenergy contained by the molecules of a body.
Heat is a cause. Temperature is an effect.

3. What do you mean by specific heat capacity of a substance?
Answer: The specific heat capacity of a substance means the amount of heat energy required to raise the temperature of 1kg mass of that substance by 1°C.

4. What is the meaning of the statement that the specific capacity of water is 4200 J/kg°C?
Answer: The specific capacity of water is 4200 J/kg°C means that 4200 J heat energy is required to raise the temperature of 1kg water by 1°C.

5. What is used to cool the engine of vehicles? Why?
Answer: Water is used to cool the engine of vehicles. It is because water has a high heat specific capacity (4200 J/kg°C). Due to this, it can absorb more amount of heat without getting hot itself and can cool the engine of vehicles easily.

6. What is used in hot water bags? Why?
Answer: Water is used in hot water bags due to its high heat specific capacity i.e. 4200 J/kg°C. Due to this, water cools down very slowly. So, the hot water can be utilized for longer time than any other liquid.

7. A new quilt is felt warmer than an old one. Why?
Answer: A new quilt has more air spaces than that of the old one. Air is a bad conductor of heat and electricity. Thus, a new quilt is felt warmer than an old one.

8. A wet handkerchief is kept on the forehead of the patient suffering from fever. Why?
Answer: A wet handkerchief is often made wet with water. Water has high specific heat capacity i.e. 4200 J/kg°C. And, the forehead of the patient suffering from fever is too hot. So, it can absorb more amount of heat energy and cool down the temperature of the patient. Therefore, a wet handkerchief is kept on the forehead of the patient suffering from fever.

9. We wear woolen clothes during winter. Why?
Answer: Air is a bad conductor of heat. Woolen clothes have more air spaces than other clothes which denies the escape of heat out from our body. This keeps our body warm. Hence, we wear woolen clothes during winter.

10. A solid melts on heating. Why?
Answer: On heating, the intermolecular forces start colliding frequently due the increase in kinetic energy. Similarly, when a solid metal is heated, the closely packed particles get converted into loosely packed particles due to collision. As a result, solid melts on heating.

11. Well water is felt warmer in winter. Why?
Answer: In winter, the surrounding temperature is colder than that of water due to high specific heat capacity of water. Thus, more heat energy flows from our body to the surrounding but less heT energy flows to the water. As a result, well water is felt warmer in winter. (Wait for the validation of this answer)

12. Write any two differences between mercury and alcohol.
Answer:
Any two differences between mercury and alcohol are:
  1. Mercury is a colorful liquid but alcohol is a colourless liquid.
  2. The boiling point of mercury is 357°C but that of alcohol is just 78°C.

13. Write any two differences between clinical thermometer and laboratory thermometer.
Answer:
Any two differences between clinical thermometer and laboratory thermometer are:
  1. A clinical thermometer has its calibration from 35°C to 42°C whereas that of an alcohol thermometer is -10°C to 110°C.
  2. A clinical thermometer is used to measure body temperature whereas an alcohol thermometer is used to measure temperature of laboratory stuffs.

14. If chilled coke and hot tea are kept together, tea cools down but coke gets warm. Why?
Answer: If chilled coke and hot tea are kept together then, the heat energy from the hot tea (hot body) flows to the chilled coke (cold body) till they attain thermal equilibrium. As a result, the hot tea cools down but the coke gets warm.

15. When a hot iron nail is kept in cold water, the temperature of iron decreases, whereas the temperature of water increases, why?
Answer: Heat is always transferred from a hot body to a cold body regardless of their internal energy. In above condition, the hot iron nail is a hot body and the cold water is a cold body. As a result, heat from the nail gets transferred to the water until they attain thermal equilibrium. Thus, the temperature of iron decreases whereas that of water increases.

About this book:

Oasis School Science Grade 10
Author: Jayananda Kapadi
Editor: Dr. Rameshwar Adhikari

About Oasis Publication:

Oasis Publication (P) Ltd.
Anamnagar, Kathmandu, Nepal
Phone: 0977-01-4224004

Here are the most important points that you need to remember from this chapter to perform well in examinations:
  1. Heat is the sum total of kinetic energy contained by the molecules of a body. Its SI unit is Joule (J).
  2. Temperature is the measure of the hotness or coldness of a body. Its SI unit is Kelvin (K).
  3. The thermometer is used to measure the temperature. Any two thermometric liquids are mercury and alcohol.

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