# Heat Energy And Its General Effects ICSE Class-7th Goyal Brothers Physics Solutions Chapter-5 Unit-1

Heat Energy And Its General Effects Class-7th Goyal Brothers ICSE Physics Solutions Chapter-5(Heat) Unit-1(Heat Energy And Its General Effects). We Provide Step by Step Answers of Objectives, Fill in the blanks, Match the following, True/False, Incorrect and Correct, Question Type answers of Chapter-5(Heat) Unit-1 (Heat Energy And Its General Effects). Visit official Website for detail information about ICSE Board Class-7.

## Heat Energy And Its General Effects ICSE Class-7th Goyal Brothers Physics Solutions Chapter-5 Unit-1

 Board ICSE Class 7th Subject Physics Book Name Goyal Brothers Chapter-5 Heat Unit-1 Heat Energy And Its General Effects Topic Solution of exercise questions Session 2023-24

### OBJECTIVE QUESTIONS

Heat Energy And Its General Effects ICSE Class-7th Goyal Brothers Physics Solutions Chapter-5 Unit-1

#### Que: A. Fill in the blank spaces by choosing the correct word from the list given below :

List : Sun, condensation, temperature, melting, sublime

1. A fixed temperature at which a solid changes into liquid state is called melting point.

2. The process due to which a gas changes into liquid state at fixed temperature is called condensation.

3. When a solid directly changes to gaseous state on heating, without changing to the liquid state, the gaseous material so formed is called sublime.

4. The heat energy brings about a change in the temperature of a material body.

5. On the surface of the earth, sun is the prime source of energy.

#### Que: B. Statements given below are incorrect. Write the correct statements :

##### Question: 1. The freezing point of a liquid and melting point of a solid of same material have different numerical values.

Answer: The freezing point of a liquid and melting point of a solid of same material have same numerical values.

##### Question: 2. The fixed temperature at which a solid changes into liquid state with the release of heat energy is called melting point.

Answer: The fixed temperature at which a solid changes into liquid state with the absorb of heat energy is called melting point.

##### Question: 3. Heat is a visible energy which determines the flow of energy.

Answer: Heat is a invisible energy which determines the flow of energy.

##### Question: 4. One joule is the amount of energy required to raise the temperature of 1 g water through 1 °C.

Answer: One joule is the amount of energy required to raise the temperature of 1 g water by 1 °C.

##### Question: 5. The fossil fuels, wood and biomass are obtained from the dead plants and animals.

Answer: The fossil fuels, wood and biomass are obtained from the dead and decay of plants and animals.

#### Que: C. Write ‘True’ or ‘False’ for the following statements :

 Statements True/False 1. Vaporization takes place at fixed temperature. T 2. Wood is a flammable substance. T 3. Iodine melts on heating. F 4. Fixed temperature at which a solid changes into gaseous state is called vaporization. F 5. Wet clothes when spread in sunshine do not dry easily. F

#### Que: D. Tick (√) the most appropriate answer :

##### 1. The wet clothes dry due to the process of :

(a) vaporisation

(b) evaporation

(c) sublimation

(d) liquefaction

Answer: option (b) evaporation is correct.

##### 2. A small piece of camphor placed in sunshine disappears due to the process of :

(a) evaporation

(b) vaporisation

(c) sublimation

(d) none of these

Answer: option (c) sublimation is correct.

##### 3. A vapour is a gaseous state of liquid :

(a) below the boiling point of liquid

(b) above the boiling point of liquid

(c) at the boiling point of liquid

(d) none of these

Answer: option (a) below the boiling point of liquid is correct.

##### 4. When calcium carbonate is heated, it changes to calcium oxide and carbon dioxide. The change brought about by the heat energy is :

(a) change of state

(b) change of dimensions

(c) change of temperature

(d) chemical change

Answer: option (d) chemical change is correct.

##### 5. Which will not undergo sublimation?

(a) Ammonium chloride

(b) Camphor

(c) Sodium chloride

(d) Iodine

Answer: option (c) Sodium chloride is correct.

#### Que: E. Match the statements in Column A, with those in Column B :

 Column A Column B 1. The process due to which a liquid changes to gaseous state at a fixed temperature by the absorption of heat energy. (a) Rise in temperature 2. A change takes place in a substance on the absorption of heat energy when no change of state or dimensions takes place. (b) Sublimation 3. A process due to which a solid directly changes to gaseous state on the absorption of heat energy. (c) Evaporation 4. A process due to which certain substances burn in air or oxygen releasing a large amount of heat energy. (d) Vaporisation 5. The process of change of liquid into gas at any temperature. (e) Combustion

 Column A Column B 1. The process due to which a liquid changes to gaseous state at a fixed temperature by the absorption of heat energy. (a) Vaporisation 2. A change takes place in a substance on the absorption of heat energy when no change of state or dimensions takes place. (b) Rise in temperature 3. A process due to which a solid directly changes to gaseous state on the absorption of heat energy. (c) Sublimation 4. A process due to which certain substances burn in air or oxygen releasing a large amount of heat energy. (d) Combustion 5. The process of change of liquid into gas at any temperature. (e) Evaporation

### STUDY QUESTIONS

Heat Energy And Its General Effects ICSE Class-7th Goyal Brothers Physics Solutions Chapter-5 Unit-1

#### 1. (a) Define heat energy and its units.

Answer: Heat is a form of energy which flows. It is the energy of motion of molecules constituting the body.
The unit of heat is same as that of energy, The S.I. unit of heat is joule (abbreviated as J) and other common units of heat are calorie and kilo calorie, where 1 k cal = 1000 cal.

#### (b) Name four effects which the heat energy can bring about in a material body.

Answer: Heat energy brings about change in dimensions:- When a material body (solid, liquid, or gas) is supplied with heat energy, its dimensions change, i.e., on the absorption. of heat energy, the length, the area, and volume of the body increase.

#### 2. What do you understand by the term “change of state”?

Answer: The physical process where matter moves from one state to another is said to be a change of state. Examples of change of state are melting, boiling, evaporation, condensation, freezing, crystallization, and sublimation.

#### 3. Define the following :

##### (a) Fusion

Answer: The process of causing a material or object to melt with intense heat.

##### (b) Fusion point

Answer: The temperature at which melting takes place

##### (c) Solidification

Answer: A phase transition in which a liquid turns into a solid when its temperature is lowered below its freezing point

##### (d) Solidification point

Answer: The temperature at which solidification starts taking place

#### 4. (a) How do the fusion point and solidification point of ice and water compare numerically?

Answer: Melting point is the same as fusion point and solidification point is also called freezing.

Because melting point and freezing point describe the same transition of matter, in this case from liquid to solid (freezing) or equivalently, from solid to liquid (melting).

What you may not realize is that while water is freezing or melting, its temperature is not changing! It is stuck on 0 ∘C0 ∘C during the entire melting or freezing process. It is easier to see this for boiling points. if you put a thermometer in water and heat it, the temperature will rise until it reaches 100 ∘C100 ∘C, and then it starts boiling. And while it boils, it will stay at 100 ∘C100 ∘C! All the way until the water has all boiled away. Now if you could somehow trap the steam (gaseous water) and keep heating it, the steam could have a temperature higher than 100 ∘C100 ∘C.

So to sum this all up, when matter is transitioning from solid to liquid (melting) or liquid to solid (freezing), its temperature is fixed at the melting/freezing point, which is the same temperature.

#### (b) Describe different sources of heat energy.

Answer: The different sources of heat energy are the sun, earth, wood and biomass, coal and petroleum.

1. The Sun:- The primary source of heat energy on the earth’s surface is the sun. Heat and light energy is produced because of the fusion of hydrogen atoms in sun.
2. Earth:- We can produce superheated steam by pumping water from deep inside of the earth in a volcanic region. This superheated steam can be used as heat energy for various purposes.
3. Wood and Biomass:- Heat energy can be produced from wood and biomass by burning them. Dried leaves, cow dung, or any other non-usable products of animals and vegetables are the constituents of biomass. Biomass can be converted into combustible gases such as methane, which on combustion will give us heat energy.
4. Coal and Petroleum:- The forests got buried under the earth’s surface, got converted into coal or petroleum due to the slow action of heat and pressure in the earth. Coal and petroleum produces heat energy on burning.

#### 5. Define the following :

##### (a) Vaporisation

Answer: Vaporisation can be defined as the process in which the liquid state changes into the vapour state.

##### (b) Vaporisation point

Answer: Vaporisation can be defined as the process in which the liquid state transforms into the vapor state. The fixed temperature at which a liquid state is converted into a gaseous state due to the process of vaporisation is known as the vaporisation point.

##### (c) Condensation

Answer: Condensation is the process through which the physical state of matter changes from the gaseous phase into the liquid phase.

##### (d) Condensation point

Answer: Condensation point is the temperature at which a gas changes into its liquid state.

#### 6. How do the vaporisation point of water and condensation point of steam compare numerically?

Answer: Condensation point is the constant temperature at which gas converts into the liquid state in the process of condensation. Vaporisation point is the constant temperature at which liquid converts into the gaseous state in the process of vaporisation. The vaporisation point of a liquid and condensation point of a gas is having the same numerical values, so the condensation point of steam and vaporisation point of water is having the same numerical value. 100°C is the vaporisation point of water and as well as the condensation point of steam.

#### 7. (a) What is evaporation.

Answer: evaporation is a form of vaporisation in which a liquid or solid is transformed into vapour. It involves a change in the state of matte

#### (b) Give two differences between vaporisation and evaporation.

 Vaporisation Evaporation Vaporisation is defined as the phase transition of a compound or an element that occurs during the boiling or sublimation process. Evaporation is nothing but a type of vaporisation which mostly occurs at temperatures below the boiling point. Vaporisation can change the state of matter from a solid or liquid to a gas. During evaporation, the liquid state of matter is turned directly into a gas.

#### 8. (a) What do you understand by the term sublimation?

Answer: We can define sublimation as the transition of a substance from the solid phase to the gaseous phase without changing into the liquid phase. This process is an endothermic phase transition that occurs at a temperature and pressure below the triple point of the substance.

#### (b) Give two example of the substances which sublime.

Answer: Sublimation is a process of converting a solid into a vapor state directly by heating it without going through the liquid state. Two substances that can sublime are:

• Camphor. (solid)
• Iodine. (solid)

#### 9. Give two example to prove that heat energy brings about a chemical change.

Answer: Burning of substances like charcoal, paper or wood undergo a chemical change and gives carbon dioxide gas and water vapor with the release of large amounts of heat energy.

#### 10. By giving four example each, define:

##### (a) Flammable substances

Answer: Flammable materials are those that catch fire readily. For example- wood, kerosene etc.

##### (b) Non-flammable substances

Answer: Flammable materials are those that do not catch fire. For example, glass, steel.

— : end of Heat Energy And Its General Effects ICSE Class-7th Goyal Brothers Physics Solutions Chapter-5 Unit-1 :–-