Thermal properties of matter describe how a substance behaves in response to changes in temperature or heat.
1. Temperature and Heat
- Temperature: A measure of the average kinetic energy of the particles within a substance. It determines the direction of heat flow (from hotter to colder objects).
- Heat: The transfer of thermal energy between objects or systems at different temperatures.
2. Heat Capacity and Specific Heat
- Heat Capacity (C): The amount of heat required to raise the temperature of a substance by 1 degree Celsius (or 1 Kelvin).
- Specific Heat Capacity (c): The amount of heat required to raise the temperature of 1 unit mass of a substance by 1 degree Celsius (or 1 Kelvin).
- Relationship: C = mc (where m is the mass of the substance)
3. Thermal Expansion
- Concept: Most substances expand when heated and contract when cooled.
- Linear Expansion: The change in length of a solid when its temperature changes.
- Volume Expansion: The change in volume of a solid, liquid, or gas when its temperature changes.
- Applications: Bimetallic strips, expansion gaps in bridges and railway tracks.
4. Thermal Conductivity
- Concept: The ability of a material to conduct heat.
- Good conductors: Materials that transfer heat quickly (e.g., metals).
- Poor conductors (insulators): Materials that transfer heat slowly (e.g., wood, air).
- Applications: Cooking utensils, insulation in buildings.
5. Heat Transfer
- Conduction: Heat transfer through direct contact (mainly in solids).
- Convection: Heat transfer through the movement of fluids (liquids and gases).
- Radiation: Heat transfer through electromagnetic waves (can occur in a vacuum).
- Applications: Heating systems, cooling systems, solar radiation.
6. Change of State
- Melting: The transition from solid to liquid.
- Freezing: The transition from liquid to solid.
- Boiling: The transition from liquid to gas.
- Condensation: The transition from gas to liquid.
- Sublimation: The transition from solid to gas directly.
- Deposition: The transition from gas to solid directly.
- Latent Heat: The heat absorbed or released during a change of state without a change in temperature.
7. Thermodynamics
- Study of heat and its relation to other forms of energy: Includes concepts like internal energy, work, and heat transfer.
- Laws of thermodynamics: Fundamental principles governing thermal processes.