Thermal Physics

Question 1

What is Heat?

Answer 1

The spontaneous transfer of thermal energy, between two object caused by a difference in temperature.

Question 2

What is the Symbol and Units of Heat?

Answer 2

Symbol: Q
Units: Joules

Question 3

Why is heat transfered from one object to another?

Answer 3

because energy want sto be spread evenly and thus have energy spread equally between them

Question 4

What is Temperature?

Answer 4

A measure of the average kinetic enrgy of the particles

Question 5

What is the Symbol and Units of Temperature?

Answer 5

Symbol: θ or T
Units: K (for T) °C or K (for θ)

Question 6

What is 0K in °C?

Answer 6

-273°C

Question 7

What is Specific Heat Capacity?

Answer 7

The amount of energy required to change 1kg of material by 1K

Question 8

What is the equation that links Heat and Specific Heat Capacity?

Answer 8

Q = mcΔθ
Q = Thermal energy (heat)
m = Mass
c = Specific Heat Capacity
Δθ = Change in temperature (K or °C)

Question 9

What is the Units and Symbol for Specific Heat Capacity?

Answer 9

Symbol: c
Units: J/(kg x K)

Question 10

What is Specific Latent Heat?

Answer 10

The amount of energy required to change the state of 1kg of a material, without changeing its temperature

Question 11

What is the equation that links Specific Latent Heat and Heat?

Answer 11

Q = mL
Q = Thermal Energy (heat)
m = Mass
L = Specific Latent Heat

Question 12

What are the two types of Specific Latent Heat?

Answer 12

Specific Latent Heat of Fusion:
Solid ⇌ Liquid
Specific Latent Heat of Vaporisation:
Liquid ⇌ Gas

Question 13

What is the Units and Symbol for Specific Latent Heat?

Answer 13

Symbol: L
Units: J/kg

Question 14

What assumptions are made about ideal gasses?

Answer 14

Molecules are point masses.
Molecules move in random directions.
Collisions are elastic.
Time taken for collisions is negligable compared to time inbetween.

Question 15

When does a real gas behave like an ideal gas?

Answer 15

When temperatures are high (incomparison to bp)

When pressure is low

Question 16

What is an Ideal Gas?

Answer 16

A model used to explain the behavior of a gas

Question 17

What is the equation for Pressure?

Answer 17

P = F/A
P = Pressure
F = Force
A = Area

Question 18

What is the Symbol and Units of Pressure?

Answer 18

Symbol: P
Units: N/m²

Question 19

What affects the Pressure of a Gas?

Answer 19

Volume
Kinetic energy
Amount of Gas
Temperature

Question 20

What are the Gas Laws?

Answer 20

They describe how Pressure, Temperature and Volume are related

Question 21

What is Boyle’s Law?

Answer 21

pV = Constant
p ∝ 1/V
At a Constant Temperature

Question 22

What is Charles’ Law?

Answer 22

V/T = Constant
V ∝ T
At a Constant Pressure

Question 23

What is the Pressure Law?

Answer 23

p/T = Constant
p ∝ T
At a Constant Volume

Question 24

What is the equation, when the three gas laws are combined?

Answer 24

pV/T = Constant

Question 25

What are the two Ideal Gas Equations?

Answer 25

``` pV = nRT = NkT p = Pressure V = Volume n = number of moles R = gas constant N = Number of molecules k = Boltzmann constant T = Temperature ```

Question 26

What is the Area of a Pressure-Volume graph?

Answer 26

Work Done

Question 27

If a gas is compressed quickly what will happen?

Answer 27

It will increase in temperature to increase causing pressure to increase. Thermal energy cannot be lost to the surroundings fast enough ∴ both pressure and temp increase

Question 28

If a gas a gas is compressed slowly what will happen?

Answer 28

It will increase in pressure. | It won't increase in temperature as thermal energy is able to be lost to the surroundings

Question 29

What assumptions are made by the Kinetic Theory of an Ideal Gas.

Answer 29

Molecules are point masses Molecules have continuous random motion No intermolecular forces Collisions are elastic

Question 30

What is the equation for the Kinetic Theory of an Ideal Gas?

Answer 30

``` pV = (1/3)Nm(Crms)² p = Pressure V = Volume N = Number of Molecules m = Mass of Molecule Crms = Root mean square speed of the molecules ```

Question 31

How is an rms calculated?

Answer 31

Square all the values in the data set Take a Mean of the square values Root the Mean

Question 32

What is the equation for the Average Molecular Kinetic Energy?

Answer 32

``` E = 0.5m(Crms)² = 1.5kT = 3RT/2N E = Energy m = Mass Crms Root mean square speed k = Boltzmann Constant T = Temperature R = Gas Constant N = Number of Molecules ```