Thermal Properties of Matter - Important Formulas, Definitions, and Examples | 11th Physics

Chapter 7: Thermal Properties of Matter

Formulas: Heat, Temperature, Specific Heat Capacity, Latent Heat, Thermal Conductivity

Introduction

This chapter focuses on the thermal properties of matter, which include the way substances respond to changes in temperature and heat. The key concepts include heat transfer, the behavior of materials under heat, and the laws governing these changes.

1. Heat and Temperature

Definition:

Heat is the form of energy transferred between two bodies at different temperatures. It is measured in joules (J).

• Formula: Q = m × c × ΔT, where Q is the heat transferred, m is the mass of the substance, c is the specific heat capacity, and ΔT is the change in temperature.

Temperature is the measure of the average kinetic energy of particles in a substance. It is measured in degrees Celsius (°C), Kelvin (K), or Fahrenheit (°F).

2. Specific Heat Capacity

Definition:

Specific Heat Capacity is the amount of heat required to raise the temperature of one unit mass of a substance by one degree Celsius or Kelvin.

• Formula: c = Q / (m × ΔT), where c is the specific heat capacity, Q is the heat supplied, m is the mass, and ΔT is the temperature change.

Key Points:

• Substances with higher specific heat capacity require more energy to heat up.
• Water has a high specific heat capacity, making it useful for regulating temperature.

3. Latent Heat

Definition:

Latent Heat is the amount of heat required to change the state of a substance without changing its temperature. It is categorized into Latent Heat of Fusion (solid to liquid) and Latent Heat of Vaporization (liquid to gas).

• Formula: Q = m × L, where L is the latent heat and m is the mass.

4. Thermal Expansion

Definition:

Thermal Expansion is the tendency of matter to change in shape, area, and volume in response to a change in temperature. It is explained in terms of linear, areal, and volumetric expansions.

Linear Expansion:

• Formula: ΔL = α × L₀ × ΔT, where α is the coefficient of linear expansion, L₀ is the original length, and ΔT is the change in temperature.

Volume Expansion:

• Formula: ΔV = β × V₀ × ΔT, where β is the coefficient of volume expansion, V₀ is the original volume, and ΔT is the change in temperature.

5. Thermal Conductivity

Definition:

Thermal Conductivity is a property that measures a material’s ability to conduct heat. Materials with high thermal conductivity, such as metals, are good conductors of heat, whereas those with low thermal conductivity, such as wood or plastic, are insulators.

• Formula: Q/t = k × A × (ΔT/L), where k is the thermal conductivity, A is the area, ΔT is the temperature difference, and L is the thickness of the material.

6. Newton’s Law of Cooling

Definition:

Newton’s Law of Cooling states that the rate of heat loss of a body is directly proportional to the difference in temperature between the body and its surroundings.

• Formula: dT/dt = -k (T - Tₐ), where T is the temperature of the object, Tₐ is the ambient temperature, and k is a constant.