Thermal Physics

Question 1

What are the 6 state changes?

Answer 1

• Solid to Liquid - Melting
• Liquid to Gas - Boiling/Evaporation
• Gas to Liquid - Condensation
• Liquid to Solid - Freezing/Solidification
• Solid to Gas - Sublimation
• Gas to Solid - Deposition

Question 2

What is the temperature at Absolute Zero?

Answer 2

0 Kelvin

-273°C

Question 3

What is Absolute Zero?

Answer 3

The point at which atoms have the least possible kinetic energy

Question 4

What is the Kinetic Model of Matter

Answer 4

The study of the relation between average internal kinetic energy and temperature

Question 5

What is the effect of a change in temperature on pressure?

When there is a constant volume

Answer 5

T ∝ P

Directly proportional

Question 6

What is the effect of a change in volume on pressure?

When there is a constant temperature

Answer 6

T ∝ 1/P

Inversely proportional

Question 7

What is the formula for the relationship between pressure and volume?

Answer 7

pV = constant

p = Pressure (Pa)
V = Volume (m³)

Question 8

Def. Internal energy

Answer 8

A measure of the average kinetic energy of the particles in a substance

Question 9

How does internal energy present istelf?

Answer 9

Temperature

Question 10

Def. Specific Heat Capacity

Answer 10

The energy needed to the change the temperature of a unit mass by a unit temperature

Question 11

What is the formula for Specific Heat Capacity?

Answer 11

C = ΔE/(mΔT)

C = Specific Heat Capacity(J/(kgK) or Jkg^-1K^-1)
ΔE = Change in Energy (J)
m = Mass (kg)
ΔT = Change in Temperature (K)

Question 12

Explain the process of evaporation

Wording is important

Answer 12

• Occurs when a liquid turns into a gas
• The liquid does not need to boil for evaporation to occur
• Particles need a certain amount of kinetic energy to escape the surface of the liquid
• When a particle escapes the surface, the average energy of the liquid left behind wil decrease

Question 13

What are the three factors that affect evaporation?

Answer 13

• Temperature
• Surface Area
• Removal of vapours from liquid surface

Question 14

How does surface area affect evaporation?

Answer 14

An increase in surface area will lead to an increase in evaporation because a larger surface means more particles can evaporate at once

Question 15

How does temperature affect evaporation?

Answer 15

An increase in temperture will lead to an increase in evaporation as average kinetic energy of particles is increased so they are more likely to evaporate

Question 16

How does the rate of removal of vapours from the liquid surface affect evaporation?

Answer 16

As this rate increases, evaporation increases because the vapours will make it harder for evaporation to occur, slowing the rate of evaporation

Question 17

What is Conduction?

Answer 17

A transfer of thermal energy that occurs in solids in which particle vibration, ineternal kinetic energy, is transfered to neighbouring particles.

Question 18

Term for

Poor conductor

Answer 18

Insulator

Question 19

What main factor makes a good conductor?

Answer 19

Delocalised electrons which have a very low specific heat capacity so kinetic energy can be transfered quickly

Question 20

What is the experiment to measure the conductivity of a metal?

Answer 20

Heat a bar of the material to which thumbtacks are attached with vaseline at regular intervals

Question 21

What is Convection?

Answer 21

A transfer of kinetic energy that occurs in fluids (liquids and gases) by the diffusion of particles carrying internal kinetic energy throughout the fluid

Question 22

Describe the process of convection

Answer 22

• Water close to a heat source gains thermal energy and becomes less dense
• The less dense, hot water rises and coller water replaces it
• As the water rises, it cools, and sinks back down, replacing hot water
• The cycle repeats

Question 23

What is Radiation?

Answer 23

A transfer of energy that can occur in a vacum, normally by infrared waves

Question 24

What are the properties of black materials in terms of radiation?

Answer 24

• Good thermal energy absorbers
• Bad radiation emitters

Question 25

What are the properties of white materials in terms of radiation?

Answer 25

• Bad thermal energy absorbers
• Good radiation emitters

Question 26

What are the differences between dull and shiny materials in terms of infrared radiation absorbtion and emission?

Answer 26

Dull materials are good absorbers and bad emitters, while it is the opposite for shiny surfaces

Question 27

Describe the radiation of an object at a constant temperature

Answer 27

An object at a constant temperature absorbs and emits energy at the same rate

Question 28

Def. Brownian Motion

Answer 28

Brownian motion is the random movement of particles in a liquid or a gas produced by large numbers of collisions with smaller (faster moving) particles which are often too small to see

Question 29

What causes microscopic particles to move randomly?

Answer 29

Light, fast-moving atoms and molecules collide with the larger microscopic particles
The collisions give the particles a little nudge, causing them to change their speed and directions randomly, each time they are struck by a molecule