Energy Transfer by Heating - P2

What is thermal conductivity?

How quickly energy is transmitted through a material by thermal conduction

How do you test Thermal Conductivity?

Using a bunsen burner, tripod and waxed rods, where each rod must have the same diameter and length, and the same temperature difference between its ends. One end of each rod is covered in wax and the others ends are heated equally. The faster the wax melts, the higher the thermal conductivity of the metal

When a substance is heated or cooled the temperature change depends on:

The substances mass, the type of material, and how much energy is transferred to it

What is Specific Heat Capacity?

The amount of energy needed to raise the temperature of 1kg of a substance by 1°c

How do you calculate the change in thermal energy?

Change in Thermal Energy (J) = mass (kg) x specific heat capacity (j/kg°c) x temperature change (°c)

Which factors affect the rate of heat loss from a building?

The thickness of its walls and roof, and the thermal conductivity of its walls and roof

How can thermal conductivity be reduced?

By using thermal insulators

What does the rate of energy transfer per second through a material depend on?

The materials thermal conductivity, the temperature difference between the two sides of the material, and the thickness of the material

What do all objects do?

Emit and absorb infrared radiation

What does emit mean?

To give out

What does absorb mean?

To take in

A good absorber of infrared radiation is also a what?

Good emitter

What happens to infrared radiation for an object at a constant temperature?

The amount of infrared radiation emitted is equal to the infrared radiation absorbed, and the infrared radiation is emitted across a continuous range of wavelengths

The higher the temperature of an object, the _______ infrared radiation it emits in a given time

More

When will an objects temperature increase?

When it absorbs infrared radiation at a higher rate than it emits it

What is a black Body?

A theoretical object that absorbs 100% of the radiation that falls on it.

Finish the sentence: A perfect black body would not…

Reflect or transmit any radiations, and would also be a perfect emitter of radiation

What do greenhouses gases do?

Absorb infrared radiation emitted by the surface of the Earth and prevent it escaping back into space. They then re-emit the infrared radiation back towards the surface of the earth, increasing the earths temperature

What do greenhouse gases in the earths atmosphere include?

Water vapour, methane, and carbon dioxide