Thermal Physics

Question 0

Absolute zero

Answer 0

The lowest possible temperature, at which an object has minimum internal energy

Question 1

What is the absolute scale?

Answer 1

A temperature scale in kelvin, defined in terms of absolute zero, 0K, and the triple point of water, 273K

Question 2

Absolute temperature

Answer 2

Temperature in Celsius + 273

Question 3

What is boiling point?

Answer 3

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

Question 4

What is Boyle’s law?

Answer 4

For a fixed mass of gas at constant temperature, it’s pressure x volume is constant

Question 5

What is the Boltzmann constant?

Answer 5

The molar constant / Avogadro number

Question 6

What is Brownian motion?

Answer 6

The random and unpredictable motion of a particle such as smoke particle caused by molecules of the surrounding substance colliding at random with the particle

Question 7

What is Charles’ law?

Answer 7

For an ideal gas at constant pressure, it’s volume is directly proportional to it’s absolute temperature

Question 8

What is heat (Q)?

Answer 8

Energy transferred due to a difference in temperature

Question 9

What is heat capacity?

Answer 9

The energy required to change the temperature of a substance by 1K

Question 10

What is an ideal gas?

Answer 10

A gas under such conditions so that is obeys Boyle’s law

Question 11

What is the ideal gas equation?

Answer 11

pV=nRT

n= number of moles, R= the molar constant

Question 12

What is internal energy?

Answer 12

The sum of the random distribution of the kinetic and potential energies of a substance’s molecules

Question 13

What is the kinetic energy if the molecules in an ideal gas?

Answer 13

Mean kinetic energy = 3/2kT

Total kinetic energy = 3/2nkT

Question 14

What is the kinetic theory of a gas?

Answer 14

Molecules are in continual random motion so pressure is pV=1/3Nmc^2

Question 15

What is the latent heat of fusion?

Answer 15

The energy required to change the state of a liquid to solid (or vice versa) without a change in temperature

Question 16

What is latent heat of vaporisation?

Answer 16

The energy required to change a liquid to a gas (or vice versa) without a change in temperature

Question 17

What is melting point?

Answer 17

The temperature at which a pure substance’s state changes from a solid to liquid

Question 18

What is metastable state?

Answer 18

An excited state of the nuclei of an isotopes that lasts long enough after alpha or beta emission for the isotope to be separated from the parent isotope

Question 19

What is a moderator?

Answer 19

Substance in a thermal nuclear reactor that slows down the fission neutrons so the they can go on to produce further fission

Question 20

What is the nucleus?

Answer 20

The relatively small part of an atom where all the atom’s positive charge and most of its mass is concentrated (1/10th size of the atom)

Question 21

What is pair production?

Answer 21

When a gamma photon changes into a particle and antiparticle

Question 22

What is a photon?

Answer 22

Wave packet of electromagnetic radiation

E=hf

Question 23

What is the pressure law for an ideal gas?

Answer 23

Its pressure is directly proportional to its absolute temperature

Question 24

What is sublimation?

Answer 24

The change of state when a solid changes to vapour directly

Question 25

What is thermal equilibrium?

Answer 25

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

Question 26

What is specific heat capacity?

Answer 26

The quantity of thermal energy required to raise the temperature of unit mass of a substance by a unit temperature

Question 27

What is the relationship between temperature and energy transfer?

Answer 27

Temperature determines the direction in which thermal energy will be transferred Thermal energy is transferred from a region at a higher temperature to a region of lower temperature

Question 28

Define thermal equilibrium

Answer 28

Regions of equal temperature are in thermal equilibrium, where there is zero resultant energy transfer between them

Question 29

What factors effect internal energy?

Answer 29

Temperature —> if temp increases, molecules travel more rapidly, KE increases, internal energy increases Pressure —> (not ideal gas) Pressure decreases (with no change in temp), gas expands, work done on molecules to pull them apart, therefore increase in P.E. and increase in internal energy State — increase in potential energy

Question 30

Define an ideal gas

Answer 30

A gas that has internal energy only in the form of random kinetic energy

Question 31

Define internal energy of a body

Answer 31

The sum of the random distribution of kinetic and potential energies of all the molecules in the body

Question 32

Pressure =

Answer 32

Force (F) / Area (A)

Question 33

Define phase

Answer 33

Phase means whether a substance is a solid, liquid or gas

Question 34

What is the ideal gas equation?

Answer 34

pV = nRT ``` p = Pressure (Pa) V = Volume (m^3) n = number of moles R = gas constant (8.31 JK^-1 mol^-1) T = temperature (K) ```

Question 35

Charles' Law

Answer 35

The volume occupied by a gas at a constant pressure is directly proprtional to its thermodynamic (absolute) temperature

Question 36

Boyle's Law

Answer 36

The pressure exerted by a fixed mass of gas is inversely proportional to its volume, provided the temperature remains constant

Question 37

State three assumptions of the kinetic model of ideal gases

Answer 37

Particles move with random, rapid motion There are no intermolecular forces Collisions are elastic

Question 38

Use kinetic theory of gases to explain how a gas exerts a pressure

Answer 38

Molecules continually collide with the walls of a container By doing this, force is exerted on the walls of the container This force is spread over the area of the container, which results in pressure being exerted

Question 39

State two conclusions about air molecules that may be deduced from Brownian Motion

Answer 39

Smoke molecules are larger than the air molecules Air molecules are in perpetual random motion at different speeds

Question 40

Explain the term thermal equilibrium

Answer 40

Where the temperature of the two regions is equal, so there is no net heat exchange