Heat transfer occurs when there is a difference in temperature between two areas. The energy naturally flows from the area of higher temperature to the area of lower temperature.

Conduction is the process by which thermal energy (heat) travels through solids. This happens because the particles in a solid are tightly packed together in fixed positions.

How Conduction Works

1. In a solid, particles are closely packed and vibrate in their fixed positions.
2. When the solid is heated, thermal energy is transferred to the particles, increasing their kinetic energy.
3. As the particles gain kinetic energy, they vibrate more vigorously.
4. These vibrations are passed from one particle to the next, allowing the heat to spread through the solid.

Metals are excellent conductors of heat because, in addition to particle vibrations, they have "free" electrons that move through the solid, carrying energy with them. This makes heat transfer through metals faster than through non-metals.

Convection is the transfer of heat through fluids (liquids and gases) by the movement of the fluid itself.

How Convection Works 5. When a fluid is heated, the particles gain energy and move faster, causing the fluid to expand and become less dense. 6. The warmer, less dense fluid rises, while the cooler, denser fluid sinks. 7. This creates a convection current that transfers heat throughout the fluid.

Radiation is the transfer of heat through electromagnetic waves, such as infrared radiation. Unlike conduction and convection, radiation does not require a medium and can occur in a vacuum.

How Radiation Works

• All objects emit thermal radiation based on their temperature.
• The hotter an object, the more radiation it emits.
• This energy can travel through space and be absorbed by other objects, increasing their temperature.

Insulation works by reducing the rate of heat transfer. Air is a poor conductor of heat because its particles are far apart, making it difficult for heat to transfer. This property of air can be used to prevent heat loss from objects.