Thermal Flashcards
(43 cards)
What is the kelvin?
Base unit of temperature starting at the lowest possible temperature absolute zero
What is the internal energy of a system?
Energy of molecules due to their individual movements and positions.
Only changes that can cause a change if internal energy of a system are work done or heating.
What can change the internal energy of a system?
Only changes that can cause a change if internal energy of a system are work done or heating.
What is sensible heat?
Energy required to change the temperature of the substance without changing its state.
What is the specific heat capacity of an object?
The energy required to raise 1kg of a substance by 1 kelvin
What happens to the kinetic and potential energies of the molecules upon sensible heating?
The bonds holding the molecules together are broken down decreasing the potential energy as they gain kinetic energy increasing their freedom of movement.
What is latent heat?
Energy required to change the state of a 1kg of a substance
What is the specific latent heat of vaporisation of a material?
Energy required too vaporise 1kg of a liquid at its vaporisation point.
What is the specific latent heat of fusion of a material?
Energy required to melt 1kg of a solid at its melting point.
What is thermal equilibrium?
Any two objects that are at the same temperature, no overall energy transfer
What is the equation relating specific heat capacity (c), Change in energy (ΔQ), mass and Change in temperature (Δθ)?
ΔQ = mcΔθ
What energy changes occur during fusion?
Latent heat is released as a substance solidifies as the molecules slow down (Ep increases and Ek decreases)
What is the equation latent heat (l), Change in energy (ΔQ) and mass?
ΔQ = ml
What energy changes occur during vaporisation?
As a result of an increase in temperature, the kinetic energy of the molecules increases. Due to the increase in kinetic energy, the force of attraction between the molecules reduces as well as the potential energy.
What is sublimation?
Solid that vaporises directly when heated
On a temperature time graph, how can you calculate power?
P = mcΔT / Δt
On a temperature time graph, why does a solid with a larger specific heat capacity have a higher gradient?
The liquid heats up ‘faster’
What is pressure?
Force per unit area exerted normally on a surface in Pascals, Pa
What is Boyle’s law?
For a fixed mass of gas at constant temperature, pressure is inversely proportional too the volume.
What is Charles’ law?
For a fixed mass of gas at a constant pressure, Volume is directly proportional too the temperature.
What is change called if it is made at a constant temperature?
Isothermal
As stated by Charles’ law, Why is the volume directly proportional too the temperature?
When work is done too change the volume of the gas, energy must be transferred as heating in order to remain at a constant pressure.
How do you calculate the work done (ideal gases)?
w = p. ΔV
Why do molecules exert a force o the walls of their container?
Their momenta change as they change direction, N2 a force is exerted on the particles by the wall, N3 the particles exert a force on the wall.
