Thermal Physics Y10

Thermal Physics Y10

So far we have seen...

• That temperature is a measurement of the average KE of the molecules.

• 2 different scales: Celsius and Kelvin.

• That specific heat capacity is the amount of energy needed to raise one degree to one kilogram of a material.

Multiple Choice

Do two objects at 10°C have the same temperature?

• TRUE

• FALSE

Multiple Choice

If an object has a specific heat capacity of 250 J/kg°C it means that...

• The object needs 250 J to change its state.

• The object needs 250 J to raise 1°C.

• The object needs 250 J to raise 1°C to 1 kg.

Multiple Choice

Copper has a specific heat capacity of 385 J/kg°C.

How much thermal energy does a copper bar of 3 kg need to raise its temperature from 25°C to 85°C?

• 69,300 J

• 30,300 J

• 21,900 J

• 8,900 J

TODAY: changes of state

• To melt something we need energy.

• To boil something we also need energy.

• While the change of state is going on, there is NO change in temperature.

Basically all the thermal energy is being used to change the state of the material.

Instead of "specific heat capacity", we now use "specific latent heat" (L)

The specific latent heat is: the amount of energy needed to change the state of 1 kg of material.

Rearranging we can also see that Q = L*m

Using the formula on the right, calculate:

• How much is the energy needed to fully melt 2 kg of ice at 0°C?

• ^{(specific latent heat of ice = 334,000 J/kg)}

Multiple Choice

Answer to the previous question:

• 889,000 J

• 668,000 J

• 223,000 J

• 1 J

Multiple Choice

While changing state, does matter also change its temperature?

• TRUE

• FALSE

• Depends

Multiple Choice

While changing state, does matter also change its temperature?

• TRUE

• FALSE

• Depends