Physics OCR A A Level - Thermal

describe the solid state of matter

fixed lattice of particles close together, performing simple harmonic motion about fixed points, vibrating with increased amplitude when temperature increases

describe the liquid state of matter

no regular structure, particles can move around each other

describe the gas state of matter

random speed and direction

with an ideal gas internal energy = ? energy

? = kinetic

What are all of the assumption made for an ideal gas (modelled by the kinetic theory of gases)

1. perfectly elastic collisions

2. particles occupy negligible volume compared to the container

3. electrostatic forces between particles outside of collisions are negligible

4. no KE transferred to the container

5. large number of particles in random motion

define the specific heat capacity

energy required per unit mass to change the temperature by 1degrees Celsius/ Kelvin

define internal energy

sum of the kinetic and potential energy of all the atoms of a substance

define absolute zero

minimum temperature where KE is zero (0K or -273.15 Celsius)

if the gradient of a temperature against time graph for substance A is steeper than substance B then what can be said about the specific heat capacity of it

A has a smaller specific heat capacity than B

c = specific heat capacity = ?

? = ΔE/mΔθ

what is the shape of a pressure against 1/volume graph (assuming a constant temperature)

straight line through the origin

state Boyle's Law

pressure is inversely proportional to volume at a fixed temperature and fixed amount of gas

how to demonstrate Boyles law

connect a pressure gauge and gas syringe slowly lower a gas syringe to reduce friction

PV = n?

n = number of moles

? =RT

T= absolute temperature (Kelvin)

R = molar constant = 8.31 (Jmol-1K-1)

PV = N?

N = number of particles

? = kT

k = Boltzmann constant = 1.38*10^(-23) (JK^-1)

T = absolute temperature

what are on the axes of the Boltzmann-Maxwell distribution graph

the number of particles against molecular velocity

if the temperature increases, what happens to the shape of the Boltzmann-Maxwell distribution

1. peak at a larger speed

2. broader distribution

3. shorter peak

define the specific latent heat

energy required per unit mass to change the state of a substance at a constant temperature

what states are involved in specific latent heat of fusion

solid, liquid

what states are involved in specific latent heat of vaporisation

liquid, gas

mass / molar mass = ?

? = number of moles

mass/ (nucleon number *AMU) = ?

? = number of particles

Boltzmann constant/ molar constant = k/R = ?

? = 1/avogadro's constant = 1/(6.023*10^23)

PV = (1/3)?

? = Nm(mean speed squared)

m = mass of a single particle

N = number of particles

square all individual molecular speeds, calculate their average (mean)

E = (3/2)?

E = average kinetic energy

? = kT

k = Boltzmann constant = 1.38*10^(-23)

molar mass/ avogadro's constant = ?

? = m

m = mass of a particle

P = (1/3) ? (mean speed squared)

? = density

average kinetic energy is proportional to ?

absolute temperature

how to increase the accuracy of thermal physics experiments

1. higher resolution thermometer

2. stir water bath

3. leave thermometer to reach thermal equilibrium

4. calculate average

5. insulation

6. control experiment with no heater

State Charles' Law

volume is directly proportional to absolute temperature at a fixed pressure and a fixed amount of gas

Method to estimate absolute zero

1. sealed container of air

2. placed in a water bath with a thermometer

3. heat water

4. plot pressure against temperature

5. extrapolate to x intercept

how to determine a specific heat capacity of a substance using method of mixtures

1. two different temperature, different substance with known masses

2. one of the substances must have a known specific heat capacity

3. mix the two substances and wait until thermal equilibrium

4. if no heat lost to surroundings then energy lost from hotter substance = energy gained by colder substance = ΔE

5. calculate ΔE by using known specific heat capacity

6. unknown c =ΔE/mΔθ

equation for combined gas law

P1V1/T1 = P2V2/T2

how to determine specific heat capacity of a substance using an immersion heater and what uncertainties can occur

1. place the material in the immersion heater surrounded by insulation

2. place the thermometer in the immersion heater

3. ammeter in series to heater

4. voltmeter in parallel to heater

5. E = Pt = IVt

6. c = E/mΔT

UNCERTAINTIES

1. heat loss to the surroundings

2. if liquid material, stir so temperature varies less

3. some energy increases temperature of the container

4. temperature will continue to rise after heater is turned off

what causes pressure in a container filled with gas

collision of gas particles with the container

E = (1/2)?

E = average kinetic energy

? = m(mean speed squared)

what do the following symbols stand for

M = ?

m = ?

M = molar mass

m = mass

what can be said about the kinetic energy and potential energy of gases, liquids and solids when the same temperature

kinetic energy is the same

gases have higher potential energy than liquids which have higher potential energy than solids