Temperature
Measure of how hot or cold something is and the average kinetic energy of particles in a sample of substance
Temperature scales
Also known as absolute temperature scales
Celsius, Fahrenheit, Kelvin
Thermal equilibrium
Two objects in contact long enough will reach thermal equilibrium and attain the same temperature
Physical properties that depend on temperature
Thermometric properties:
- Volume of a liquid
- Electrical resistance
- Colour of a filament
- Length of a rod
Absolute Zero in Temperature
0 K
-273,15°C
Average temperature of universe
2,73K
Internal Energy (U)
The sum of potential and kinetic energies of the particles in a substance
Thermal energy transfer
Thermal energy will always be transferred from a region of higher temperature to region of lower temperature
If temperature rises
Internal energy of a substance also rises
Temperature change (rate of increase/decrease) will only be the same if
It is the exact same material and mass
Kinetic energy
Energy due to motion
Potential energy
Energy due to position, arrangement and intermolecular forces
Thermal expansion explanation
An increase in temperature causes an increase in average kinetic energy of particles and particles move faster. This results in more energetic collisions which push neighbouring molecules further apart (causing expansion)
Thermal expansion
A fractional change in size of a material in response to a change in temperature
Anomalous behaviour of water
- Water particles have strong forces (intermolecular forces) between them, hydrogen bonding
- Liquid water, particles have a lot of average kinetic energy, so forces cannot hold it in rigid structure
- Particles slip and slide past each other quite closely, forces in between constantly break and re-form (spaces are small, liquid quite dense)
- Water becoming solid, forces rearrange particles in rigid hexagonal structure (big spaces)
- Spaces are bigger than in water in liquid phase, so ice is less dense and floats
Specific Heat Capacity
Of a substance is the amount of heat energy required to raise the temperature of 1 kg of the substance by 1 K
Relationships in Q formula
ΔT VS Q Directly proportional
ΔT VS m Inversely proportional
Formula for amount of heat energy added or removed
Q = cmΔT
Important formulas to know
W = F.Δx
V = W/q
W = V.q
P = W/t
q = I.t
Unit of c
J.kg-1.K-1
During a phase change
Energy is added from an outside source and this energy is used to break the attractive force between particles and increase the potential energy of particles
Evaporation
The vaporisation of liquid particles from the surface of the liquid usually accompanied by a decrease in temperature
Boiling
Vaporisation of the liquid particles from the bulk liquid, occurring only through the addition of heat and with no change in temperature
Specific Latent heat fusion
The amount of heat energy required to convert 1 kg of a substance from a solid to a liquid at the melting point (constant temperature)
