Thermal
Define 'Temperature'
The average KE of particles in a substance
What is thermal energy equal to?
Total KE
Define 'Heat'
The total KE of particles, it's thermal energy that is transmitted from one object to another
Define 'Absolute Zero'
The temperature which a substance has minimun internal energy (lowest limit for temperature)
Define 'Internal Energy'
The sum of the randomly distributed kinetic & potential energies of all atoms and molecules within a system
What's the principle of thermal equilibrium
Two systems are in equilibrium if there's no net flow of thermal energy between them when connected by a path permeable to heat
How do you convert from °Celsius to °Kelvin
°K = °C + 273
Describe the model of a Solid
- Particles vibrate in a fixed ordered lattice
- Held by strong intermolecular forces
- Have low energies compared to liquids and gases
Describe the model of a Liquid
- Held by weak intermolecular forces
- Can flow past each other
- Closely packed
Describe the model of a Gas
- Particles are spread out
- Particles only exert a force on each other when they collide
- Particles move in a random linear motion with random speeds
Define 'Brownian Motion'
The erratic movement of small particles when observed through a small microscope
Define 'Specific Heat Capacity'
The energy needed to raise the temperature of 1kg by 1°K(Units JKg^-1K^-1)
Give a formula that links Energy & SHC
E = mcΔθ
E = Energy
m = Mass
c = SHC
Δθ = Change in temperature
What happens when substances change from either solid to liquid or liquid to gas
- EPE of molecules increase
- Bonds between molecules break & molecules move further apart
- KE remains the same, so temperature remains the same
What happens when substances change from either gas to liquid or liquid to solid
- EPE of molecules decrease
- Bonds between molecules form and they move closer together
- KE remains the same, so temperature remains the same
Define 'Specific Latent Heat of Fusion
The energy needed to change the state of 1kg from a solid to a liquid
Define 'Specific Latent Heat of Vaporisation'
The energy needed to change the state of 1kg from a liquid to a gas
Give a formula that links SLH and Energy
E = mL
E = Energy
m = Mass
L = Specific Latent Heat
Give the formula for number of moles
n = m/M
n = no of moles
m = mass
M = molar mass
Give the formula for no of particles in a substance
p = n*(6.02×10^23)
p = no of particles
n = no of moles
(6.02×10^23) = Avogadro's Constant
Give 4 assumptions that are used to model an ideal gas
- Gas contains a large no of particles
- Particles move rapidly and randomly
- All collisions are elastic(KE is conserved)
- There are negligible attractive forces between particles except during collisions
- Particles have a negligible volume compared with the volume of gas in a container
- The time for a collision to happen is negligible to the time taken between collisions
Collisions between atoms and the walls of containers are elastic, what does this tell you about the speed of the atom before and after the collision
It is the exact same
What does Newtons 3rd law suggest about the pressure of a container
The total pressure is equal to the sum of the force of each collision on the wall divided by the area of the wall
State 'Boyle's Law'
If the temperature of an ideal gas and mass is constant, pressure is inversely proportional to volume
State 'Charles Law'
If the pressure of an ideal gas and mass is constant, Volume is proportional to temperature
Give the ideal gas equation (FOR THE NO OF MOLES)
pV = nRT
p = pressure
V = Volume
n = no of moles
R = molar gas constant
T = Temperature(°K)
Give the ideal gas equation (FOR THE NO OF MOLECULES)
pV = NkT
p = pressure
V = Volume
N = no of molecules
k = boltzmann constant
T = Temperature(°K)
Define 'Mean square speed'
The mean value of the square of velocity for a large no of gas particles
Give the mean square speed equation
pV = 1/3Nmc̅²
p = Pressure
V = Volume
N = No of molecules
m = Mass(of single molecule)
c̅² = Mean square speed
What does the area under the Maxwell Boltzmann distribution graph show us
The total number of molecules
Give one other feature that the Boltzmann distribution shows us
The greater the temperature of gas, the peak of the graph has a higher speed, so the distribution is more spread out
Give an equation linking the two equations for pressure
kt = 1/3Nmc̅²
Give the formula for the mean KE of gas molecules
KE = 3/2kt
Give an equation linking KE and pressure
3/2kt = 1/3Nmc̅²
Why is KE equal to the total internal energy of an ideal gas and what does this show
Thers's no electrostatic forces between atoms in ideal gases, so there's no potential energy, so the internal energy would only consist of KE.
- Shows temperature is proportional to internal energy
Describe an experiment to prove boyle's law
- Using a clamp stand to hold a syringe
- Measure the internal diameter of the syringe using vernier callipers
- Place a nozzle over the syringe
- Place the pinch clip over the nozzle
- Attach a string to the end of the syringe & place a 100g mass on it (Wait a bit for temp to be constant as work is done)
- Take the volume reading and find pressure by (mg/A)
- Add another 100g mass
- Repeat the last 2 steps 8 times
- Plot a graph 1/v against P
- If the graph is straight, then the relationship is correct
Describe an experiment to prove Charles Law
- Measure internal diameter of capillary tube with callipers to get area
- Make sure a capillary tube is closed on one end and open on the other (Keeps pressure at atmospheric pressure)
- Add a drop of sulphuric acid halfway in the capillary tube
- Place tube in a beaker with a thermometer
- Use two rubberbands to hold ruler next to tube
- Boil water and let it cool a bit before pouring in beaker
- Find the volume of the gas by doing Area x height & find temp using thermometer
- Repeat the last step 8 times each time letting the temp decrease by 5
- Plot a graph volume against temp
- If relationship is right, the graph will be a straight line graph
*EXTRAPOLATE TO FIND ABSOLUTE ZERO*