Thermal Physics

Question 1

Internal energy of an object

Answer 1

The sum of the random distribution of the kinetic and potential energies of its molecules.

Question 2

First law of thermodynamics

Answer 2

The change of internal energy of the object = the total energy transfer due to work done and heating.

Question 3

Solid

Answer 3

The atoms and molecules are held to each other by forces due to the electrical charge of the protons and electrons in the atoms. Molecules vibrate randomly about fixed positions.

Question 4

Liquid

Answer 4

The moelcules move about at random in contact with each other. The forces between the molecules are not strong enough to hold the molecules in fixed positions.

Question 5

Gas

Answer 5

The molecules also move about randomly but much further apart on average than in a liquid.

Question 6

Thermal equilibrium

Answer 6

A state of a system in which all parts are at the same temperature.

Question 7

Ice point

Answer 7

0 degrees celsius

Question 8

Steam point

Answer 8

100 degrees celsius

Question 9

Absolute zero

Answer 9

0 K

Question 10

Triple point of water

Answer 10

273.16 K

Question 11

Temperature in celsius

Answer 11

Absolute temperature in kelvins - 273.15

Question 12

Absolute zero definition

Answer 12

The lowest possible temperature, an object at absolute zero has minimum internal energy.

Question 13

Specific heat capacity, c, of a substance

Answer 13

The energy needed to raise the temperature of unit mass of the substance by 1 K without change of state.

Question 14

The unit of specific heat capacity

Answer 14

J kg^-1 K^-1

Question 15

The energy needed to raise the temperature of a substance of mass, m from T1 to T2

Answer 15

ΔQ = mc (T2 - T1)

Question 16

Sublimation

Answer 16

The process by which some solids vaporise directly when heated.

Question 17

The specific latent heat of fusion, l, of a substance

Answer 17

The enegy needed to change the state of unit mass of the substance from solid to liquid without change of temperature.

Question 18

The specific latent heat of vaporisation of a substance

Answer 18

The energy needed to change the state of unit mass of the substance from liquid to vapour without any change of temperature.

Question 19

The energy, Q, needed to change the state of mass, m, of a substance from liquid to vapour without change of temperature.

Answer 19

Q = m x l

Question 20

Pressure of a gas definition

Answer 20

The force per unit area that the gas exerts normally on a surface.

Question 21

Boyle’s law

Answer 21

pV =constant

Question 22

Isothermal change

Answer 22

Change at constant temperature.

Question 23

Isobaric change

Answer 23

Change at constant pressure.

Question 24

Charle’s law

Answer 24

V/T = constant

Question 25

Work done by a gas on a piston

Answer 25

p ΔV

Question 26

The pressure law

Answer 26

p/T = constant

Question 27

Brownian motion

Answer 27

Term used to describe the motion of individual molecules in a gas.

Question 28

The Avogrado constant, NA

Answer 28

6.023 x 10^23, the number of atoms in exactly 12g of the carbon isotope 12C6.

Question 29

Definition of one mole

Answer 29

The quantity of substance that contains NA particles. Unit is the mol.

Question 30

The molar mass of a substance

Answer 30

The mass of 1 mol of the substance.

Question 31

An ideal gas

Answer 31

A gas that obeys Boyle's law, the three experimental gas laws can be combined to give the equation pV/T - constant, for a fixed mass of ideal gas.

Question 32

Ideal gas equation

Answer 32

pV = nRT

Question 33

Molar gas constant, R

Answer 33

8.31 J K^-1 mol^-1

Question 34

Boltzmann constant, k

Answer 34

1.38 x 10^-23 J K^-1

Question 35

Kinetic theory equation

Answer 35

pV = 1/3 N m (Crms)^2

Question 36

Assumptions made about molecules in gas

Answer 36

The volume of each molecule is negligible compared with the volume of the gas. Molecules do not attract eachother and move about in continual random motion. Collisions are elastic.

Question 37

Kinetic energy of gas molecule

Answer 37

1/2 m (Crms)^2 = 3/2 k T = 3RT/2NA