Definitions 3: Thermal Physics

Question 1

Thermal Equilibrium

Answer 1

When two bodies are in thermal equilibrium, there is no net flow of thermal energy between the bodies that are in thermal contact because they are at equal temperature.

Question 2

Heat

Answer 2

The thermal energy that flows from a region of higher temperature to lower temperature.

Question 3

Thermometric Property

Answer 3

a property of a substance that changes with temperature.

Question 4

Thermodynamic Temperature

Answer 4

Thermodynamic Temperature does not depend on the thermometric property of any substance.
[Unit: kelvin, K]

Question 5

Absolute Zero

Answer 5

Absolute Zero is defined as the zero point (0K) and is a fixed point on the absolute temperature scale.
A substance at absolute zero has minimum internal energy.

Question 6

The kelvin

Answer 6

The kelvin is 1/273.16 the thermodynamic temperature of the triple point of water.

Question 7

Ideal Gas Law

Answer 7

An ideal gas obeys the equation of state pV = nRT, where R is the molar gas constant and n is the amount of gas (in mol), at all pressures (p), volumes (V) and temperature (T).

*Alternative: pV=NkT, where N is the number of molecules and k is the Boltzmann’s constant

Question 8

Avogadro’s Number

Answer 8

Avogadro’s number, N=6.02x10^(23)mol^(-1), is the number of atoms in 12 grams (0.012kg) of carbon-12.

One more of any substance contains 6.02x10^(23) particles.

Question 9

Assumptions of the Kinetic Theory of Gases

Answer 9

1. Gas molecules are hard, elastic identical spheres
2. Large numbers of gas molecules are in constant random motion
3. No intermolecular forces except during collisions
4. Total volume of molecules negligible compared to volume of containing vessel
5. Time of collision negligible compared to time between collisions

Question 10

r.m.s. speed

Answer 10

An indicative average speed that represents the average translational kinetic energy of gas particles.

Question 11

Specific heat capacity

Answer 11

Thermal energy per unit mass to raise the temperature of a substance by one degree.
Q=mc ΔT

Question 12

Specific latent heat

Answer 12

Thermal energy per unit mass to change the phase of a substance at constant temperature.

Specific latent heat of fusion: …… from solid to liquid state.
Specific latent heat of vaporisation: …… from liquid to gaseous state.

Q=mL

Question 13

Internal energy

Answer 13

Sum of kinetic energy due to random motion of a distribution of particles and potential energy due to intermolecular forces between the particles.

Question 14

First Law of Thermodynamics

Answer 14

The increase in internal energy of a system is the sum of heat supplied to the system and work done on the system.

Question 15

Types of Processes of gases:
Isobaric Process:
Isovolumetric Process:
Isothermal Process:
Adiabatic Process:

Answer 15

Isobaric Process: Constant pressure
Isovolumetric Process: Constant Volume
Isothermal Process: Constant temperature
Adiabatic Process: Temperature change is 0 (Too fast for heat transfer/perfect insulation)