thermal

Question 1

internal energy

Answer 1

the sum of the kinetic energy and bond total energies of the molecules of a system as measured when the system as a while is not moving

Question 2

thermal capacity

Answer 2

the amount of energy needed to raise the temperature of a substance by 1K

Question 3

specific heat capacity

Answer 3

the amount of energy needed to raise the temperature of unit mass of a substance by 1K

Question 4

specific latent heat

Answer 4

the amount of thermal energy needed to change the state of a unit mass of a substance at constant temperature

Question 5

mole

Answer 5

the amount of a substance that contains the same number of atoms as 0.012kg of carbon-12

Question 6

molar mass

Answer 6

mass of one mole of a substance

Question 7

avogadro constant

Answer 7

the number of atoms in 0.012 kg of carbon-12 (approx 6x10^23)

Question 8

pressure

Answer 8

the normal force to an area per unit area

Question 9

temperature 2

Answer 9

1) a property that determines the direction of heat flow between two bodies in thermal contact
2) a measure of the average random kinetic energy of the molecules of an ideal gas

Question 10

boiling point

Answer 10

temperature at which the vapor pressure of a liquid is equal to the pressure of the atmosphere on the liquid

Question 11

whats the volume of 1 mole of any gas at normal atmospheric pressure & a temperature of 0*C

Answer 11

22.4 litres

Question 12

difference between boiling and evaporation

Answer 12

boiling takes place throughout the liquid and always at the same temperature
evaporation takes place only at the surface of the liquid and can happen at all temperatures

Question 13

how evaporation results in drop in temperature

Answer 13

when a liquid evaporates, the fastest-moving particles leave the surface
This means that the average kinetic energy of the remaining particles is lower, resulting in a drop in temperature

Question 14

how does increasing the surface area lead to more evaporation

Answer 14

increases the number of molecules near the surface giving more of them a chance to escape

Question 15

how does blowing across the surface increase the rate of evaporation

Answer 15

after molecules have left the surface they form a small ‘vapour cloud’ above the liquid. If this is blown away, it allows further molecules to leave the surface more easily

Question 16

how does raising the temperature increase the rate of evaporation

Answer 16

increases the KE of the liquid molecules enabling more to escape

Question 17

conduction 3

Answer 17

• takes place when bodies are in contact with each other
• the vibrating molecules of one body collides with the molecules of another
• the fast moving molecules lose energy and the slow-moving molecules gain it

Question 18

the temperature of a gas in kelvin is directly proportional to

Answer 18

the average KE of a molecule

Question 19

Boltzmann constant

Answer 19

1.38x10⁻²³J/K

Question 20

Boltzmann constant

Answer 20

1.38x10⁻²³J/K

Question 21

boyle’s law

Answer 21

the pressure of a fixed mass of gas at constant temperature is inversely proportional to its volume

Question 22

why is pressure of a gas inversely related to volume?

Answer 22

as the volume of a gas is reduced it will become denser, because the molecules are pushed together
The molecules will therefore hit the walls more often, increasing the rate of change of momentum and hence the pressure

Question 23

pressure law

Answer 23

the pressure of a fixed mass of gas with constant volume is directly proportional to its temperature in kelvin

Question 24

charles’ law

Answer 24

the volume of a fixed mass of gas at a constant pressure is directly proportional to its temperature in kelvin

Question 25

why is volume proportional to temperature in kelvin at a constant pressure

Answer 25

as the temperature of the gas is increased the molecules move faster causing an increase in pressure However if the volume is increased in proportion to the increase in temperature the pressure will remain the same

Question 26

avogadros hypothesis

Answer 26

equal volumes of gas at the same temperature and pressure have the same number of molecules

Question 27

why is there no potential energy in an ideal gas

Answer 27

since gas molecules have no force between them it requires no work to move them around which means that there is no energy associated with their position

Question 28

2 ways of changing temperature

Answer 28

heating or doing work on the system

Question 29

heat

Answer 29

energy transfer without the action of a macroscopic force

Question 30

graphical representation of Boyle's law

Answer 30

since the pressure of a fixed mass of gas at constant temperature is inversely proportional to its volume, a graph of pressure against volume will be a curve

Question 31

constant temperature

Answer 31

isothermal

Question 32

constant volume

Answer 32

isochoric

Question 33

constant pressure

Answer 33

isobaric

Question 34

normal atmospheric pressure

Answer 34

101.3kPa

Question 35

what conditions are needed for the ideal gas laws to apply to real gases

Answer 35

low pressure, large volume and high temperature

Question 36

why is PE increased when molecules are squashed together?

Answer 36

bond energy increases

Question 37

why do particles in an ideal gas need to be identical

Answer 37

different ones would have different masses which would change their acceleration

Question 38

why do we assume a v large no of particles for an ideal gas

Answer 38

so results are statistically relevant - the average is more reliable with a bigger sample size

Question 39

attractive force in solid

Answer 39

tension - as molecules pulled apart they push back

Question 40

repulsive force in solid

Answer 40

normal reaction - as surfaces are pushed together the molecules push back

Question 41

thermal equilibrium

Answer 41

when the rate of energy absorption is equal to the rate of energy emission You know its reached when u keep on heating an object but its temperature remains constant

Question 42

internal energy of an ideal gas

Answer 42

molecules of an ideal gas have only KE so internal energy is the total KE of the molecules