11 Thermal Physics

Question 1

Absolute scale (Thermal)

Answer 1

1. Temperature scale in Kelvins
2. defined in terms of absolute zero, 0K,
3. and the triple point of water, 273.16 K, which is the temperature at which ice, water and water vapour are in thermal equilibrium.

Question 2

Absolute zero

Answer 2

1. The lowest possible temperature;

2. The temperature at which an object has minimum internal energy.

Question 3

Absolute temperature T

Answer 3

in kelvin = temperature in degrees Celsius + 273(.15)

Question 4

Boiling point

Answer 4

The temperature at which a pure liquid at atmospheric pressure boils.

Question 5

Celsius scale

Answer 5

1. temperature, in degrees Celsius,
2. is defined as absolute temperature (in Kelvins) minus 273.15.
3. This definition means that the temperature of pure melting ice (ice point) is 0 degrees C,
4. and the temperature of steam at standard atmospheric pressure (steam point) is 100 degrees C.

Question 6

heat Q

Answer 6

energy transfer due to a difference of temperature

Question 7

Heat capacity

Answer 7

the energy needed to change the temperature of an object by 1 K

Question 8

Heat exchanger

Answer 8

1. A steel vessel containing pipes
2. through which hot coolant in a sealed circuit is pumped, 3. causing water passing through the steel vessel in separate pipes
3. to turn to steam which is used to drive turbines.

Question 9

Internal energy, U

Answer 9

The sum of the random distribution of the kinetic and potential energies of an object’s molecules.

Question 10

Latent heat of fusion

Answer 10

the energy needed to change the state of a solid to a liquid without change of temperature

Question 11

Latent heat of vaporisation

Answer 11

The energy needed to change the state of liquid to a vapour without change of temperature.

Question 12

Specific heat capacity, c

Answer 12

1. SHC of a substance is the energy needed to raise the temperature of 1 kg of the substance, by 1 K, without change of state.
2. To raise the temperature of mass m of a substance from T1 to T2, the energy needed Q = mc (T2 - T1), where c is the specific heat capacity of the substance.

Question 13

Specific latent heat of fusion

Answer 13

SLHF of a substance is the energy needed to change the state of unit mass of a solid to a liquid without change of temperature.

Question 14

Specific latent heat of vaporisation

Answer 14

SHLV for a substance is

• the energy needed
• to change the state of unit mass of a liquid to a vapour
• without change of temperature.
• To change the state of mass m of a substance without change of temperature,
• the energy needed Q = ml, where l is the specific latent heat of fusion or vaporisation of the substance.

Question 15

Sublimation

Answer 15

The change of state when a solid changes to a vapour directly

Question 16

Temperature

Answer 16

The degree of hotness of an object

Question 17

Thermal energy

Answer 17

The internal energy of an object due to temperature

Question 18

Thermal equilibrium

Answer 18

When no overall heat transfer occurs between two objects at the same temperature