Physics thermodynamics

0th Law of Thermodynamics

If C is initially in thermal equilibrium with both A and B then A and B are also in thermal equilibrium with eachother

Ideal Insulater

Idealized material that prevents systems from attaining thermal equilibrium

Conducting material

Permits two objects to come to thermal equilibrium

Gay-Lussac's Law

P1/T1=P2/T2, for a fixed amount of gas and at constant volume, the pressure (P) of the gas is directly proportional to its absolute temperature (T).

Thermal Expansion

ΔL = αL₀ΔT (length), ΔV= βV₀ΔT (volume)

ΔT causes linear change in L₀ in solids from which ΔL is roughly proportional to L₀ and ΔT. (Same for volume).

Tensile Stress

When a heated or cooled material is held preventing contraction and expansion

Heat energy transferred (Specific heat capacity)

Q = mcΔT

c = specific heat capacity

m = mass of substance

ΔT = temp change

Heat energy transferred (molar heat capacity)

Q = nCΔT

C = molar heat capacity

n = number of moles

ΔT = temp change

Heat absorbed/released during phase change

Q=±mL

m = mass

L = latent heat of substance

• is for when heat is absorbed

• is for when heat is released

Conduction

Convection

Radiation

Conduction: Transfer of heat through a material

Convection: Transfer of heat through a fluid

Radiation: Transfer of heat through EM radiation

Formula for rate of heat transfer by conduction

Formula for rate of heat transfer by convection

Stefan - Boltzmann Law --> Rate of heat transfer by thermal radiation

H = AeσT⁴

OR

H = AeσT(T⁴ - s⁴) --> Rate of NET heat transfer

A = Surface Area

e - emissivity of object

σ = Stefan Boltzmann constant

T = absolute temp

Tripple point of water

Specific and unique temperature and pressure at which all three phases of water (solid ice, liquid water, water vapour) can coexist in stable equilibrium.

Temperature: 0.01 °C

Pressure: 611.657 Pascals (0.006037 atmospheres)

Heat

Energy in transit from one object or system to another due to a temperature difference

Ideal Gas law

pV = nRT --> R = 8.314 J/mol x K

Mole terms: pV = mtotal/M x RT

Describes relationship between pressure, volume, moles, gas constant and temperature

Behaviour of gas

1. Volume is proportional to No. of moles

2. Volume is inversely proportional to absolute pressure

3. Pressure is proportional to absolute temperature

Ideal gas

Gas which holds ideal gas law for all pressure and temperatures (is purely theoretical)

Van Der Waals Equation

Improved ideal gas law

a = constant account for attractive forces

b = constant accounting for volume occupied by gas molecules

Isotherm

Means constant temperature

In reference to a "pV - isotherm" it means a pressure - volume graph across a constant temperature

Potential well

Region in space where the potential energy is lower than surrounding regions

Mole

The amount of substance that contains 6.022 x 10^23 'elementary entities' (molecules)

Mole equations

mtotal = nM

Total mass = number of moles x Molar mass

M = Nam

Molar mass = Avogadro's number x mass of singe atom/molecule

Kinetic - molecular mode equations

Total translational kinetic energy of an ideal gas:

Ktr = 3/2xnRT

Average translational kinetic energy of a single molecule:

1/2m(v²)av = 3/2kT

Root means squared speed of an ideal gas: (typical molecular speed)

vrms = √(v²)av = √(3kT/m)

Mean free path of a molecule in a gas: (avg distance travelled between collisions)

λ = vtmean = V/(4π√(2)r²N)

Heat Capacity

Amount of heat required to raise the temperature of a substance by 1°C

Molar heat capacity is the same but for 1 mole of a substance.

Thermodynamic system

any collection of objects that is convenient to regard as a unit, and that may have the potential to exchange energy with its surroundings.

Positive and negative work

Positive work: Work done by system against surroundings

Negative work: Work done on the gas by its surroundings (energy entering the system)

Work done by molecules

When molecules collide with stationary surfaces, it exerts a momentary force on the wall but DOES NO WORK as the wall doesn't move.

A molecule striking a piston does positive work if the piston is moving away but negative work if piston is moving towards it.

Molecule

Smallest of a substance

Work done during volume changes

W = ∫pdv (from V1 to V2)

Expansion = positive work

Compression = negative work