Thermal Physics Flashcards
What is the triple point of a substance
One specific temperature and pressure where the three phases of matter can exist in thermal equilbrium
Define Thermal Equilibrium
No net transfer of thermal energy between the phases
What happens when objects are in thermal equilibrium
There is no net flow of thermal energy between them
What happens when Object A is warmer than Object B
Net flow of thermal energy is from Object A to Object B
Object A gets warmer
Object B gets colder
What is the 0th Law of Thermodynamics
If 2 objects are each in thermal equilibrium with a third, then all three are in thermal equilibrium with each other
What forms the basis of temperature
0th Law of Thermodynamics
What is needed in order to measure temperature
A scale is needed with 2 fixed points at defined temperatures
Describe the Celsius Scale
Freezing + Boiling Points as the 2 fixed points
There are 100 increments between 0 and 100 degrees celsius
Why is the Celsius scale not perfect
Freezing and Boiling Points vary at different atmospheric temperatures
What is the Absolute Temperature Scale also known as
Thermodynamic Temperature Scale
Describe the Absolute Temperature Scale
Uses triple point of pure water and absolute zero
What must any object at 100 degrees celsius be
In thermal equilibrium with boiling water
SI Base Unit for Temperature
Kelvin (K)
Kelvin Formula
Degrees Celsius + 273
What is Kelvin always
Positive
Describe Electrostatic Forces for different phases of matter
Solid - Strong
Gas - Negligible
What does the Kinetic Model describe
How all substances are made up of atoms or molecules - which are all arranged differently depending on the phases of the substance
Density in Water
Less dense in solid than in liquid
One of the rare substances to do this
What is Brownian Motion
The haphazard movement of particles of a substance caused by the transfer of momentum through elastic collisions with particles of a surrounding medium
How Brownian Motion observed
Robert Brown looked through a microscope and recorded his observations of the random arrangement of fine pollen grains floating on water
How did Einstein explain Brownian Motion
In terms of collisions between the pollen grains and millions of tiny water molecules
These collisions were elastic and resulted in a transfer of momentum from water molecules to the pollen grains which made them move in haphazard ways
How can Brownian Motion be observed
Using a smoke cell - particles of smoke are large enough to be seen under a microscope
They move in a random way and are surrounded by air molecules
Air molecules are constantly striking the smoke particles
Air molecules are in random motion
Mean KE of Smoke = Mean KE of air molecules
Air molecules of 500 ms^-1 - Smoke molecules are more massive and move much more slowly
Density for most substances between phases of matter
Most dense in solids
Lease dense in gases
Define Internal Energy
The sum of randomly distributed kinetic and potential energies of atoms or molecules within the substance
