Class 9 Physics Chapter 7 Notes 2026 – Thermal Properties of Matter (Punjab Board)

Matter is made up of tiny particles that are always in motion. When a substance is heated or cooled, its particles gain or lose energy, causing changes in temperature, size, and state. The study of these changes and how heat affects matter is called Thermal Properties of Matter.

In this chapter, you will learn about:

• How solids, liquids, and gases expand when heated.

• The specific heat capacity of substances and its importance.

• Methods of heat transfer: conduction, convection, and radiation.

• Practical applications of thermal properties in daily life, such as thermometers, bimetallic strips, and hot air balloons.

Understanding these concepts is essential to explain everyday phenomena and to solve physics problems related to heat.

MCQs – Thermal Properties of Matter

1. How do the molecules in a solid behave?

(a) Move randomly in all directions
(b) Vibrate about their mean positions ✅
(c) Rotate and vibrate randomly at their own positions
(d) Flow freely and change places

2. What type of motion is exhibited by the molecules in a gas?

(a) Linear motion
(b) Random motion ✅
(c) Vibratory motion
(d) Rotatory motion

3. Water is not used as a thermometric liquid mainly due to:

(a) Colourless
(b) A bad conductor of heat
(c) Non-linear expansion ✅
(d) A low boiling point (100°C)

4. The theory that explains the motion of particles in matter is called:

(a) Newton’s Theory
(b) Theory of Kinetic Energy
(c) Molecular Theory
(d) Kinetic Molecular Theory ✅

5. Plasma is a state of matter that contains:

(a) Neutral atoms only
(b) Only molecules
(c) Positive ions and free electrons ✅
(d) No particles

6. Which of the following is a natural example of plasma?

(a) Ice
(b) Water
(c) The Sun ✅
(d) Glass

7. What is plasma?

(a) A neutral state of matter
(b) A solid with free electrons
(c) A gas with ionized particles ✅
(d) A cold liquid

Important Short Questions – Class 9 Physics Chapter 7

1. What is meant by thermometric property of a substance? Enlist some thermometric properties.

Answer:

• A thermometric property is a physical property of a substance that changes with temperature.

• These properties are used in thermometers to measure temperature.

Examples of thermometric properties:

1. Volume expansion – liquids like mercury or alcohol expand with temperature.

2. Electrical resistance – resistance of metals changes with temperature.

3. Pressure of gas – pressure of a gas increases with temperature if volume is constant.

4. Length of solids – solids expand in length on heating.

2. Distinguish between heat and internal energy.

Answer:

• Heat:

  • It is the energy transferred from one body to another due to a temperature difference.

  • Heat flows only during a temperature difference.

  • Example: When you place a hot object in cold water, heat flows from the object to the water.

• Internal Energy:

  • It is the total energy of all the particles in a body, including both kinetic energy (motion of particles) and potential energy (forces between particles).

  • Internal energy depends on the state and temperature of the body.

  • Example: The internal energy of water increases as it is heated.

3. What do you mean by the linearity of a thermometer?

Answer:

• Linearity of a thermometer means that its scale readings increase proportionally with temperature changes.

• In other words, equal increments in temperature correspond to equal divisions on the thermometer scale.

4. Explain the Kinetic Molecular Theory of Matter and how it describes the three states of matter (solid, liquid, and gas).

Answer:

The Kinetic Molecular Theory (KMT) explains the behavior of particles in matter and how their motion determines the properties of solids, liquids, and gases.

Key Points of Kinetic Molecular Theory:

1. All matter is made up of tiny particles (atoms or molecules).

2. Particles are in constant motion, and the type of motion depends on the state of matter.

3. Particles exert forces on each other; attractive forces are stronger in solids and weaker in gases.

4. The temperature of a substance is a measure of the average kinetic energy of its particles.

Application to the Three States of Matter:

1. Solid:

   • Particles are closely packed and have strong forces of attraction.

   • Motion: Particles vibrate about fixed positions.

   • Properties: Definite shape and volume, incompressible.

2. Liquid:

   • Particles are less tightly packed than solids, with weaker attractive forces.

   • Motion: Particles can move past each other, allowing flow.

   • Properties: Definite volume but no definite shape, takes the shape of the container.

3. Gas:

   • Particles are far apart with very weak attractive forces.

   • Motion: Particles move freely and randomly at high speeds.

   • Properties: No definite shape or volume, easily compressible, and expand to fill the container.

---

📥 Download Chapter 7 Notes – Thermal Properties of Matter

Skip to PDF content

Get complete Class 9 Physics Chapter 6 notes for Punjab Board 2026, including:

• Introduction to Thermal Properties of Matter

• Temperature and Heat

• Thermal Expansion (Linear, Surface, Volume)

• Thermometric Properties

• Kinetic Molecular Theory

• Plasma and States of Matter

• Important MCQs, Short Questions, and Long Questions

📥 Click to Download Chapter 7 Notes – Thermal Properties of Matter