5.1 Thermal Physics

Question 1

Thermal Equilibrium

Answer 1

A higher temperature object in contact with a low temperature object will transfer heat from the high temperature to the lower one. The rate of change of temperature will decrease as the objects near each others temperatures, eventually they will effectively be at the same temperature.

Question 2

Features of the absolute scale of temperature (2)

Answer 2

• Starts at absolute zero

- Not dependent on any physical property of matter

Question 3

Thermodynamic Scale

Answer 3

Another name for absolute scale

Question 4

How change in Celsius relates to change in kelvin

Answer 4

They are 1 to 1

Question 5

Spacing of particles in a solid

Answer 5

Close together (high density)

Question 6

Spacing of particles in a liquid

Answer 6

Close together (high density)

Question 7

Spacing of particles in a gas

Answer 7

Sparse (low density)

Question 8

Motion of particles in a solid

Answer 8

Vibrate around a fixed equilibrium positions but have relatively small motion compared to liquid and gas

Question 9

Motion of particles in a liquid

Answer 9

Can move past each other but are still attracted

Question 10

Motion of particles in a gas

Answer 10

Move mostly freely. Almost all kinetic energy is translational (in the form of linear motion)

Question 11

Kinetic model

Answer 11

Solids, liquids and gases are made up of small moving or vibrating particles

Question 12

Brownian motion

Answer 12

The random movement of particles

Question 13

Example of Brownian motion

Answer 13

Observing smoke particles with a bright light and a microscope. They show Brownian motion.

Question 14

Internal energy

Answer 14

The sum of the randomly distributed kinetic and potential energies of all the atoms and molecules in a system

Question 15

Feature of 0K in a system

Answer 15

Minimal internal energy

Question 16

How is internal energy effected by an increase in temperature

Answer 16

increased

Question 17

Temperature of a substance that is changing state

Answer 17

constant

Question 18

A substance is heated and begins to melt. What is happening to it’s internal energy as it melts

Answer 18

It increases. (The kinetic energy stays the same but the potential energy increases)

Question 19

Maxwell-Boltzmann distribution

Answer 19

Graph of number of molecules against speed. Looks kinda similar to a normal distribution with the right side tailing

Question 20

Specific heat capacity

Answer 20

The energy required to raise 1kg of a material by 1K

Question 21

Experiment for specific heat capacity

Answer 21

Put the material in an insulator. Heat the material with an electric heater, recording the current and voltage with an ammeter and voltmeter. Record temperature with a thermometer. Once the temperature has changed by 10K calculate the total energy that went in by E = IVt and then calculate c.

Question 22

Specific latent heat

Answer 22

Energy required to change the state of 1kg of a material

Question 23

Name for specific latent heat solid->liquid

Answer 23

fusion

Question 24

Name for specific latent heat liquid->gas

Answer 24

Vaporisation

Question 25

Equation for specific heat capacity

Answer 25

E = mc(delta t)

Question 26

Equation for specific latent heat

Answer 26

E = mL

Question 27

Experiment for specific latent heat of fusion

Answer 27

Fill two funnels with the same mass of ice. Heat one of them with a heater of known power. After 10 minutes compare the amount of water that has dripped out of each one and calculate the difference in mass. Sub into E = mL to get L,

Question 28

Experiment for specific latent heat of vaporisation

Answer 28

Heat liquid to boiling point in a distilling flask. Condense the vapour given off and then divide the energy put in by the mass of the vapour. (For more accuaracy do this twice with different powers on the heater and then subtract one from the other in order to eliminate heat lost to surroundings)

Question 29

Model of kinetic theory of gases

Answer 29

Models a gas as a large number of small particles that are in constant motion and behave as an ideal gas

Question 30

Assumptions for an ideal gas (6)

Answer 30

- Large number of particles - Particles move rapidly and randomly - All collisions are perfectly elastic - Negligible forces between particles except during collision - Time for collision to happen is negligible compared to the time between collisions - Particles have negligible volume compared to that of the container

Question 31

When a real gas behaves like an ideal gas

Answer 31

Low pressure and high temperature

Question 32

Pressure as a result of a gas

Answer 32

The movement of the individual particles in a gas causes them to collide with the container walls and exerting a force on the walls

Question 33

Ideal gas equation

Answer 33

``` pV = nRT p - pressure V - volume n - number of moles R - molar gas constant T - Temperature (kelvin) ```

Question 34

Boyles law

Answer 34

Pressure is proportional to 1/Volume

Question 35

Experiment to investigate Boyles law

Answer 35

Fill a transparent tube with oil. Attach a valve, pressure gauge, scale and pump. Pump air into the system up to a high pressure. Then release a small amount of air and note the pressure from the gauge and the volume from

Question 36

Experiment to determine absolute zero

Answer 36

Fill a flask with a fixed mass of gas and attach a pressure gauge to the flask. Submerge the flask into water of varying temperature and record the pressure and temperature in each case. Plot a graph of pressure against temperature and it should be a straight line. Continuing the straight line on into the negative celsius it would cross the x axis at absolute zero.

Question 37

Experiment to determine absolute zero

Answer 37

Fill a flask with a fixed mass of gas and attach a pressure gauge to the flask. Submerge the flask into water of varying temperature and record the pressure and temperature in each case. Plot a graph of pressure against temperature and it should be a straight line. Continuing the straight line on into the negative celsius it would cross the x axis at absolute zero.

Question 38

Boltzmann constant

Answer 38

R/(NA) | Molar gas constant / Avogadro constant

Question 39

How to calculate internal energy of an ideal gas

Answer 39

Using the equation for energy of a single particle (E=1.5kT). Multiply by the number of particles

Question 40

Internal energy of an ideal gas

Answer 40

Equal to the total random kinetic energy (ideal gas has no potential energy)