Thermal Physics

What is Temperature?

Temperature is a measure of the average kinetic energy of the particles (atoms or molecules) in a substance. It is a measure of how hot or cold an object is.

Temperature Scales

• **Celsius (°C)**: The Celsius scale is based on the freezing point of water (0°C) and the boiling point of water (100°C) at standard atmospheric pressure.
• **Fahrenheit (°F)**: The Fahrenheit scale is based on the freezing point of a brine solution (0°F) and the average human body temperature (96°F).
• **Kelvin (K)**: The Kelvin scale is an absolute temperature scale, where 0 K represents the lowest possible temperature, known as absolute zero. The Kelvin scale is directly related to the average kinetic energy of the particles in a substance.

Measuring Temperature

• Thermometers are used to measure temperature. They work on the principle of thermal expansion, where a material (usually a liquid or a gas) expands when heated and contracts when cooled.
• Different types of thermometers include mercury thermometers, alcohol thermometers, and digital thermometers.

Factors Affecting Temperature

• **Heat Transfer**: Temperature changes can occur due to the transfer of heat through conduction, convection, or radiation.
• **Thermal Equilibrium**: When two objects with different temperatures are in contact, they will eventually reach the same temperature, a state known as thermal equilibrium.