Temperature

Question 1

What is meant when two objects are in thermal equilibrium?

Answer 1

Two objects are in thermal equilibrium when there is no heat transfer between them. They are at the same temperature.

Question 2

Define specific heat capacity. Provide the formula.

Answer 2

Formula: Q = mc(delta)T

It is the thermal energy required to raise the temperature of 1kg of a substance by 1ºC/ºK without changing its state.

Question 3

Define specific latent heat. Provide the formula.

Answer 3

Formula : Q = ml

It is the thermal energy required per kilogram of a substance to effect a change of state without increasing the temperature of the substance.

Question 4

WHat are the two types of specific latent heat.

Answer 4

Fusion (melting)
Evaporation

Question 5

Define specific latent heat of fusion

Answer 5

The thermal energy required per unit mass of a substance to change it from solid to liquid without a change in temperature.

Question 6

Why does melting require energy but there is no change in temperature? (3marks)

Answer 6

-When a substance melt bonds are broken.
-The kinetic energy of the particles remains constant so the temperature of the substance remains constant.
-There is an increase in potential energy so energy is equired.

Question 7

How is thermal energy transferred?

Answer 7

Thermal energy is transferred from a region of higher temperature to a region of lower temperature.

Question 8

The characteristic of the thermodynamic scale.

Answer 8

The thermodynamic scale (kelvin scale) does not depend on the property of any substance. It is based on the idea that the K.E. increases with increases in temperature

Question 9

What is the name of the lowest temperature (0K).

Answer 9

Absolute Zero

Question 10

Define specific latent heat of vaporization.

Answer 10

The energy required per unit mass of a substance to change it from liquid to gas without a change in temperature.

Question 11

Which specific latent heat is greater and why?

Answer 11

Latent heat of vaporisation > latent heat of fusion, due to the greater energy required to completely separate the molecules than to break the rigid bonds in the solid (melting involves breaking of fewer bonds per molecule); energy is required to push back the atmosphere as liquid turns to vapour, vol. of vapour > vol. of liquid