Thermodynamics Flashcards
Define Heat
The transfer of energy from one object to another.
Define Temperature
Measurement of how much heat is present in an object.
What is absolute zero?
Molecules will not be moving, therefore have no kinetic energy. 0°C = 273.15K
Kinetic Theory
Consideration of the microscopic movement of particles will predict the macroscopic behaviour of a substance.
What is potential energy?
PE is due to the binding energy in bonds between molecules.
Define internal energy.
The sum of the kinetic and potential energies of all the molecules within a given mass of a substance.
What does Maxwell-Boltzmann distribution show?
There are no molecules with zero energy.
There are only a few molecules with high energy.
There is no maximum value for the energy a molecule can have.
What happens Maxwell-Boltzmann distribution if temp increases?
The peak on the graph moves towards higher energies - higher speeds.
Zeroth Law of Thermodynamics.
Objects in thermal contact are at the same temperature.
First Law of Thermodynamics.
Energy is conserved. Change in internal energy = heat transferred + work done.
μ = Q + W
How do you calculate the root mean square.
rms = the sum of the square of individual speed of molecules divided by number of molecules, then taking the square root of that mean.
Average molecular ke
average ke is proportional to the absolute temp of the gas
1/2m = 3/2kT
Define Specific Heat Capacity.
The amount of energy required to raise the temperature of 1kg of substance by 1 Kelvin.
ΔE = mcΔθ
Define Specific Latent Heat
The energy required to change the state of a substance of 1kg at a constant temperature.
ΔE = LΔm
Black Body Radiator
Theoretical object, that absorbs and emits EM radiation at all wavelengths.
Boyles Law
For constant mass, at a constant temp, pressure is inversely proportional to volume.
Charles Law
For constant mass, at constant pressure, volume is proportional to absolute temperature.
Gay Lussacs/ Pressure Law
For constant mass, at const volume, pressure is proportional to absolute temperature.
Ideal Gas Assumptions
- Molecules have negligible size and are identical.
- Collisions are perfectly elastic.
- Molecules exert no forces on each other, except during collisions - no PE
- Motion is random
Ideal Gas Equation
pV = NkT - N is number of molecules pV = nRT - n is number of moles. R = 8.31 Jmol^-1kg^-1
Explain why the internal energy of an ideal gas is only kinetic.
as ideal gases do not have forces between molecules so no potential energy
Describe how the concept of an absolute zero of temperature arises from ideal gas laws
pV = nRT. At absolute zero, pV = zero
Describe how the concept of an absolute zero of temperature arises the kinetic model of an ideal gas
at absolute zero the molecules have
no kinetic energy, so molecules stationary
The article also states that the internal energy of the air in the balloon could become
zero if the temperature of the gas became low enough.
Explain what is meant by the internal energy of the air and discuss whether the
statement is correct.
Internal energy is the sum of the potential and kinetic energies. In an ideal gas the molecules only have kinetic energy. KE=3/2kT. Above 0K air molecules are in continual random motion. If gas reached absolute zero, KE of molecules would be zero so statement correct. If not ideal gas, molecules would have potential energy at 0K, so statement incorrect.
