Chapter 14 - Thermal Physics Flashcards
The kinetic model
Describes all substances as made up of atoms, ions or molecules, arranged differently depending on the phase.
Brownian motion
Continuous random motion of small particles suspended in a fluid, visible under a microscope.
Observing Brownian motion
Use a smoke cell and observe through a microscope.
Random motion of smoke particles caused by collisions with smaller air particles.
Internal energy
Sum of the randomly distributed kinetic and potential energies of the atoms, ions or molecules within a substance.
Changing phase
Temperature does not change, but internal energy increases as electrostatic potential energy increases (i.e. becomes less negative).
Specific heat capacity
Energy required to change the temperature of 1 kg of a substance by 1 K/1 degree Celsius.
Specific latent heat
Energy required to change the phase of 1 kg of a substance while at constant temperature.
SLH of fusion: solid to liquid
SLH of vaporisation: liquid to gas
What is absolute zero (0K)?
The lowest limit for temperature; the temperature at which a substance has minimum internal energy.
How do you determine the SHC of a substance?
Solid: use a heater with insulation.
Liquid: use calorimeter with insulation.
Thermometer - measure change in temperature.
Ammeter in series and voltmeter across heater to measure I and V.
Stopwatch
c = IVt/mΔθ OR plot θ against t, gradient is IV/mc.
Outline the method of mixtures
Mix known masses of 2 substances (at different initial temperatures).
Record final temperature at thermal equilibrium.
mcΔθ of substance 1 = mcΔθ of substance 2
Experiment to find SLH of fusion
Use thermometer to ensure ice is at melting point. Immerse heater in ice for a period of time and record I and V.
L (fusion) = IVT/m
Experiment to find SLH of vaporisation
Electric heater used with condenser to collect liquid.
Measure mass of liquid that has changed phase (i.e. from solid to liquid).
L (vaporisation) = IVT/m
Thermal equilibrium
When two or more objects in contact have the same temperature so there is no net flow of energy between them.
