Thermal Physics Flashcards
Thermal Energy
- transfer + store of energy
- transferred via conduction, convection, radiation
- increase in temperature = increase in thermal energy
States of matter
- solid
- liquid
- gas
- plasma
Plasma
- 4th state of matter
- formed when a gas becomes so hot the electrons leave the atom → form ions
Solid
- regular lattic structure
- particles vibrate around a fixed position
- closely packed
Liquid
- particles can move past each other
- still touching
- move randomly
Gas
- particles are spread out
- arranged randomly
- in a constant state of random motion
Bonds
Forces acting between particles. Forces in solids are stronger than in liquids + gases
Change of State
- solid → liquid = melting
- solid → gas = sublimation
- liquid → solid = freezing
- liquid → gas = evaporation / vaporisation
- gas → solid = deposition
- gas → liquid = condensation
Vaporisation + Evaporation
vaporisation → takes place above/at the boiling point
evaporation → takes place below the boiling point
Temperature stays the same during a change of state
energy is used to break bonds
Pressure unit
measured in Pascals (Pa)
1Pa = 1N/m2
Fluid Pressure Equation
Pressure = density x depth x gravity
P = ρ g h
General Pressure Equation
Pressure = Force / Area
P = F / A
Fluid Pressure
- exerted on the walls of a container at 90°
- acts in all directions
Why is pressure exerted by a gas on the walls of its container?
- gases are in a constant state of random motion
- the particles collide with the walls
- collisions cause a change in direction + a change in momentum
- force is exerted on the molecule → F = (mv-mu) / t
- force is exerted on the wall (Newton’s 3rd Law)
- P = F/A → pressure is exerted on the wall
Specific Heat Capacity
J/kg/°C
The energy required to increase 1kg of a substance by 1°C
ΔQ = mcΔθ
Specific Latent Heat
J/kg
Energy required to change the state of 1kg of a substance without changing its temperature
Q = mL
Breaking Bonds
Endothermic → absorbs energy
Forming Bonds
Exothermic → releases energy to the surroundings
Pressure + Temperature
If the volume of a gas is kept constant and the temperature increases:
* thermal energy increases kinetic energy of particles
* particles move more with increased velocity
* rate of collisions increases
* change in momentum per second increases
* force exerted on wall increases
* pressure increases
Absolute Zero
0K = -273°C
* particles have no kinetic energy
* no pressure is exerted
* the substance has no volume
Pressure Law
For a fixed mass of gas at a constant volume, pressure is proportional to temperature in Kelvin
Pressure + Volume
If the temperature of a gas is kept constant and the volume of gas in increased:
* rate of collisions increases
* increases change in momentum per second
* exerts a greate force on the walls
* pressure increases
Boyle’s Law
For a fixed mass of gas at a constant temperature, pressure is inversely proportional to volume
P = kV
As volume increases, pressure decreases
Plot Pressure over 1/vol to get straight lune graph
