Class 10 Physics Heat Lesson
Heat is a form of energy that transfers from one body to another due to temperature difference. It flows from a hotter body to a colder one until equilibrium is reached. The key concepts include temperature, heat transfer (conduction, convection, and radiation), specific heat capacity, change of state, latent heat capacity, evaporation, and boiling.
Lesson Summary
- Heat is a form of energy transferred due to temperature difference.
- Temperature is a measure of the average kinetic energy of particles in a substance.
- Heat transfer occurs through conduction (solids), convection (fluids), and radiation.
- Specific heat capacity is the amount of heat energy required to raise the temperature of 1 kg of a substance by 1°C.
- Changes of state involve heat energy absorption or release during melting, vaporization, condensation, and freezing.
- Latent heat capacity is the heat energy absorbed or released during a change of state without a change in temperature.
- Evaporation is the process of gradual conversion of a liquid to a gas at any temperature below the boiling point.
- Boiling is the rapid conversion of a liquid to a gas at a fixed temperature called the boiling point.
Specific Heat Capacity Example Solution
Calculate the amount of heat energy required to raise the temperature of 2 kg of water from 20°C to 50°C. Specific heat capacity of water is 4200 J/kg°C.
| Parameter | Value |
|---|---|
| Mass (m) | 2 kg |
| Specific Heat Capacity (C) | 4200 J/kg°C |
| Change in Temperature (ΔT) | 30°C |
| Heat Energy (Q) | 252000 joules |
Latent Heat Capacity Example Solution
Calculate the amount of latent heat energy absorbed when 1 kg of ice at -10°C changes to water at 0°C. Latent heat of fusion for ice is 334,000 J/kg.
| Parameter | Value |
|---|---|
| Mass (m) | 1 kg |
| Latent Heat of Fusion (L) | 334,000 J/kg |
| Latent Heat Energy (Q) | 334,000 joules |
Difference between Boiling and Evaporation
| Boiling | Evaporation |
|---|---|
| Boiling occurs at a fixed temperature called the boiling point. | Evaporation occurs at any temperature below the boiling point. |
| Boiling takes place throughout the liquid, forming bubbles. | Evaporation occurs only at the liquid's surface. |
| Boiling is a rapid process. | Evaporation is a slow process. |
| Heat energy is supplied continuously during boiling. | Evaporation occurs due to the random escape of high-energy particles. |
| Boiling causes a rapid change of state from liquid to gas. | Evaporation causes a gradual change of state from liquid to gas. |
| Examples: Boiling water on a stove, boiling water to make tea. | Examples: Drying clothes, puddles drying up on a sunny day. |