Thermal ⛆ Flashcards
Internal energy
Sum of all kinetic energies and potential energies of all its particles. The kinetic and potential energies of a body are randomly distributed
How is internal energy increased
- Increase temperature of the system
- Do work on the system to transfer energy to it
What happens when state of substance changes
Internal energy also changes due to potential energy of the system changing while the kinetic energy is kept constant
Amount of energy required to change temp of substance EQ
Q = mc△θ
Specific heat capacity of a substance
Amount of energy required to increase the temperature of a substance by 1 Celsius, without changing its state
Amount of energy required to change state of substance EQ
Q = ml
Specific latent heat of a substance
Amount of energy required to change the state of 1 kg of material without changing its temperature
1. SLH of fusion (solid to liquid)
2. SLH of vaporisation (liquid to gas)
Gas law experimental relationship
Describes the experimental relationship between pressure, volume and temperature for a fixed gas. Arose from observation and experimental in nature
- Boyles law
When temperature is constant, pressure and volume are inversely proportional
pV = k
- Charles’ law
When pressure is constant, volume is directly proportional to absolute temperature
V/T = k
- The pressure law
When volume is constant, pressure is directly proportional to absolute temperature
Kelvin scale
K = C + 273
Absolute zero (-273)
Lowest possible temperature and the temperature at which particles have no kinetic energy and the volume and pressure of a gas are zero
Ideal gas EQ (for n moles)
pV = nRT
Ideal gas EQ (for N molecules)
pV = NkT
1 mole of a substance
6.02 x 10^23 atoms/molecules
Avogadro EQ
n = N/NA
Molar mass
One mole of a substance found by finding the relative molecular mass, which is approx equal to the sum of nucleons in a molecule of the substance
Work done = p△V
Work is done on a gas to change its volume when it is at a constant temperature, the value can be found using this equation
Brownian motion
Random motion of larger particles in a fluid caused by collisions surrounding particles, and can be observed through looking at smoke particles under a microscope
- Boyle’s law kinetic theory
If you increase the volume of a fixed mass of gas, its molecules will move further apart so collisions will be less frequent therefore the pressure decreases
- Charles’ law kinetic theory
When the temperature of a gas increased, its molecules gain energy meaning they will move more quickly and because pressure is constant, the molecules move further apart and volume is increased
- Pressure law kinetic theory
When the temperature of a gas is increased its molecules gain kinetic energy meaning they will move more quickly, as volume is constant the frequency of collisions between molecules ad their container increases and they collide at higher speeds therefore pressure is increased
Assumptions of kinetic theory model
- No intermolecular forces act on the molecules
- The duration of collisions is negligible in comparison to time between collisions
- The motion of molecules is random and experience perfect elastic collisions
- The motion of the molecules follows Newton’s law
- The molecules move in straight lines between collisions
Kinetic energy of a single gas molecule
1/2m(Crms)^2 = 3/2kT = 3RT/2NA
Behaviour of gas over time
Gas laws discovered and later explained by the development of kinetic theory which was not initially accepted. Knowledge and understanding of any scientific concept changes over time in accordance to the experimental evidence gathered by scientific community
