Thermal Physics

Question 1

Temperature simple definition

Answer 1

Temp is the measure of the average kinetic energy of ta substances particles

Question 2

Equation for Power -

Answer 2

P = IV

Question 3

Equation for Energy

Answer 3

E = PT

Question 4

How can we calculate energy from Current and Voltage?

Answer 4

E = IVT

Question 5

What is conduction?

Answer 5

Conduction is a passing vibration from a high temperature.

Question 6

Why might metals conduct more than wood?

Answer 6

Because of free moving electrons which increases conduction

Question 7

Why does heat conduct faster in metals?

Answer 7

Because metals are better conductors than, eg. wood, meaning the rate of conduction will be increased (rate of energy transfer)

Question 8

What effect does surface area have on conduction?

Answer 8

Larger surface area to volume ratio means it will conduct heat quicker making it a better conductor.

Vice versa, a smaller surface area to volume ratio means the rate of conduction will be lower.

Question 9

How does a larger mass affect insulation?

Answer 9

More mass means a smaller surface area to volume ratio, therefore the heat is insulated more and the rate of conduction is lower.

Question 10

How does the difference in room temperature and water temperature affect rate of conduction?

Answer 10

The higher the difference between room and water temperature, the higher the rate of conduction.

Question 11

What is important to remember about change in temperature and difference in temperature?

Answer 11

Rate of Change of Temperature is proportional to the Difference in Temperature

Question 12

What is thermal conductivity?

Answer 12

Thermal conductivity is the energy transferred per second through an insulating material

Question 13

What is the relation between thermal conductivity and energy transfer?

Answer 13

The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material.

Question 14

What does the thickness of an insulating material do?

Answer 14

The thicker the insulating layer, the lower the rate of energy transfer through it.

Question 15

What are the 3 types of energy transfer?

Answer 15

• Conduction
• Convection
• Radiation

Question 16

What are some examples of insulation in buildings?

Answer 16

• Loft Insulation
• Cavity Wall Insulation
• Double-Glazed Windows
• Aluminium Foil behind Radiators
• External Walls with Thicker Bricks

Question 17

What are physical changes?

Answer 17

Physical Changes are change which are REVERSIBLE and include changing state

Question 18

What are chemical changes?

Answer 18

Chemical changes are when a chemical reaction occurs, and involve the formation of new chemical elements or compounds

Question 19

What can happen if one heats something up?

Answer 19

If one transfers thermal energy to something, it can either INCREASE IN TEMPERATURE or CHANGE STATE

Question 20

Note

Answer 20

Really need to understand the Temp / Time graph in book

Question 21

What is the specific heat capacity?

Answer 21

The energy required to increase the temperature of 1kg of a substance by 1°C

Question 22

What is the specific latent heat?

Answer 22

The energy required to change the state of 1kg of a substance WITHOUT A CHANGE IN TEMPERATURE.

Question 23

What are the two different phases of specific latent heat?

Answer 23

Fusion - From solid to liquid

Vaporisation - From liquid to gas

Question 24

What is the formula for the Specific Heat Capacity?

Answer 24

Energy / Mass Change x Change in Temperature

ΔE / mΔθ

Question 25

What is the unit for specific heat capacity?

Answer 25

J / Kg°C

Question 26

What is the formula for Specific Latent Heat?

Answer 26

Energy / Mass

E / M

Question 27

What are the implications of water having a high specific heat capacity?

Answer 27

Water can absorb a large amount of heat, meaning there will not be a significant rise in temperature despite the large amount of energy.

Water can MINIMISE CHANGES in TEMPERATURE.

Eg. Specific Heat Capacity of water is 5X greater than that of the land, (sand), so the land cools down far faster than the sea once the sun goes down

Question 28

What is the internal energy of an object?

Answer 28

The sum of the KINETIC and POTENTIAL energies of all its particles.

Question 29

What is the kinetic energy when measuring an energy transfer?

Answer 29

It is to do with the speed of the particles, eg. Increase in temperature means particles move faster.

Question 30

What is the Potential Energy when measuring an energy transfer?

Answer 30

Potential energy is to do with the separation of the particles, eg. Changing state when a liquid vaporises to a gas means the particles will expand which increases its potential energy.

Question 31

What is important to remember when considering potential and kinetic energy during an energy transfer?

Answer 31

Potential energy can stay the same while kinetic energy can stay the same, vice versa. This can be seen in the Temp / Time Graph!!! (When the line levels out there is an increase in potential energy (when changing state) and when the gradient of the line increases the kinetic energy is increasing.)

Question 32

What is the specific heat capacity of Water?

Answer 32

4,200 J/Kg°C

Question 33

Required Practicals -

Answer 33

• Measuring Specific Heat Capacity

- Thermal Insulation

Question 34

How to answer a 6 marker -

Answer 34

TALK ABOUT EQUATION!!!

Eg.

1. Equation
2. Measurements
   
   • Current with Ammeter
   • Voltage with Voltmeter
   • Calculation (ΔE = IVT)
   • Measuring Mass with balance
   • Talk about initial temp and final temp (with thermometer)
   • Calculate Δθ

ETC.

Question 35

How are the following measured?

P.D. 
Ɪ
T
θ
M

Answer 35

P.D. = Voltage (voltmeter)

Ɪ = Current (ammeter)

T = Time (stopwatch)

θ = Temperature (thermometer)

M = Mass (balance / scales)