P2: Energy Transfer by Heating

What is thermal conductivity?

Higher thermal conductivity means energy is transferred through a material by conduction at a faster rate.

How does thermal conduction occur in solids?

• Heating particles causes them to vibrate more rapidly and collide with neighboring particles.

• Energy is passed sequentially through the lattice from particle to particle.

Why are metals particularly good thermal conductors?

Free delocalised electrons gain kinetic energy and move quickly throughout the structure, transferring energy rapidly through collisions with metal ions.

What factors affect the rate of cooling of a building?

• The thickness of the building walls.

• The thermal conductivity of the wall materials.

• The temperature difference between the inside and outside of the building.

What is infrared radiation?

Electromagnetic waves that transfer thermal energy from a hotter body to a cooler surrounding without requiring a physical medium.

Which surfaces are the best emitters and absorbers of thermal radiation?

Matt black surfaces are the best absorbers and best emitters of infrared radiation.

Which surfaces are the worst emitters and best reflectors of thermal radiation?

Shiny silver surfaces are the worst absorbers, worst emitters, and best reflectors of infrared radiation.

What is the relationship between an objects temperature and its infrared radiation output?

As an object gets hotter, it emits a higher intensity of infrared radiation and the wavelength of maximum intensity becomes shorter.

What is specific heat capacity?

The amount of energy required to raise the temperature of one kilogram of a substance by one degree Celsius.

What does a high specific heat capacity mean for energy storage?

Materials with a high specific heat capacity store a large amount of thermal energy per degree of temperature rise and heat up or cool down slowly.

How does loft insulation reduce thermal energy loss?

Traps pockets of air to prevent convection currents and relies on the low thermal conductivity of trapped air to reduce heat loss by conduction.

How does double glazing reduce heat loss through windows?

Creates a thin vacuum or dry air gap between two glass panes to eliminate conduction and convection energy transfers.

What is a U-value in home insulation?

A measure of how fast heat travels through a building material, where a lower U-value indicates a better insulato