Thermal Flashcards
What is meant by absolute 0 or 0K (Kelvin)
The minimum internal energy of a system
What is Kelvin
- Unit of (Thermo-Dynamic) Temperature
- Absolute Scale of temperature
What is the conversion from Kelvin to Celsius
+273.15
Define the internal energy of a gas.
The sum of the randomly distributed kinetic and potential energies of the molecules within the system
How can the internal energy of a gas be changed, and explain how it changes.
Heating -> Provides more Ke to the molecules
Doing work (e.g. Compressing) -> Increases potential energy (Electrostatic repulsion) between particles
Define sensible heat
Heat or energy which changes the temperature of the substance (Affects the kinetic energies of the molecules), Hardly affects potential energies at all
Define Latent Heat
Heat or energy which changes the state of a substance, not the temperature (Affects potential energies of the molecules)
What is specific heat capacity of an object, and of a material.
The EXACT amount of energy needed to raise the temperature of 1Kg of a material by 1 degree (Either Celsius or Kelvin, equivalent by adding a constant)
What happens to the internal energy of a material during latent heating.
Potential energy will change (Increase as molecules get closer together), Kinetic energy will be largely unaffected.
Define specific latent heat of vaporisation
The exact amount of energy to change 1Kg of a substance from a liquid to a gas At Constant Temperature
(Or Gas to Liquid)
Define specific latent heat of fusion
The exact amount of energy to change 1Kg of a substance from a liquid to a solid At Constant Temperature
(Or Solid to Liquid)
What happens to the internal energy of a material upon sensible heating
Kinetic energy is affected (Increases), potential energies are almost entirely unaffected
Describe the temperature time graph for a block of ice turning to a gas through heating.
Temperature increases with constant gradient up to melting point (273.15K).
gradient decreases to 0 as energy is provided to break intermolecular bonds. (Latent heating)
gradient increases again as sensible heating is done to increase temperature to 373.15K
gradient decreases to 0 again as energy is provided to change state (Latent heating)
What quantity is the gradient of a temperature / time graph equal to and how is it derieved.
Using Q = mc(Delta)T which is on the data sheet
we can divide by (delta)time in both
giving us Power = mc(Delta)Temp/(Delta)Time
dividing by mc where m = mass and c = specific heat capacity
we get Gradient = Power / (Mass X Specific Heat Capacity)
