Heat Transfer - Term 4 2025

How does heat move?

Heat always moves from the hotter object/environment to the cooler object/environment UNTIL an equal temperature is achieved

Does radiation require a medium?

No. Radiation can transfer heat energy in the absence of a medium, it does not need a material to travel through

Does conduction require a medium?

Yes. It requires a medium/material called a conductor to be transferred, the vibration of atoms causes kinetic energy to be transferred from atom to atom

What is convection?

Convection is the transfer of heat through the movement of fluids (liquids and gases), where atoms are not tightly held in position

What happens to the atoms in a fluid when heat increases?

Their kinetic energy increases, causing them to move apart, become less dense, and rise

What happens to a fluid as it loses heat?

Its atoms lose kinetic energy, move closer together, become denser, and sink

Why does a heated fluid rise during convection?

Because increased kinetic energy makes atoms spread out, reducing density and causing the fluid to rise

How does density change during convection when heat is gained or lost?

Gaining heat decreases density (fluid rises); losing heat increases density (fluid sinks)

What is a conductor in terms of heat transfer?

A conductor allows heat to transfer because its atoms or electrons are free to move and pass on kinetic energy

Why can conductors transfer heat effectively?

Because their atoms or electrons are free to move and can pass kinetic energy to neighbouring particles

What is an insulator in terms of heat transfer?

An insulator does not allow heat to transfer because its atoms or electrons are tightly bound and cannot move freely

Why do insulators prevent heat transfer?

Because their particles are not free to move, so they cannot pass on kinetic energy

How do conductors and insulators differ in atomic structure?

Conductors have free-moving particles; insulators have tightly bound particles

What are examples of thermal conductors?

Copper, aluminium, silver, gold

What are examples of thermal insulators?

Wood, plastic, rubber, foam

How does air act as a thermal insulator?

Air traps heat poorly due to its low density and particle spacing, making it a good insulator in materials like foam or double glazing