Thermal Physics Flashcards
What is absolute zero
Lowest theretically possible temperature which is zero kelvin or -273 degrees
What is usual room temperature and atmospheric pressure at sea level
Room temperature : 20 degrees, 293 Kelvin
Atmospheric pressure (at sea level) : 101 kPa
What is boyles law
Pressure of gas is inversely proportional to volume
At a fixed mass of gas and at a constant temperature
For boyles law, draw a graph of pressure against volume. Draw two graphs with one v having a higher temperature
State Charles law
A fixed mass of gas at a constant pressure, has volume of gas directly proportional to temperature
Draw a graph to represent Charles’ law and draw two graphs with one having a higher pressure
State the pressure law (Gay-Lussacs law)
A fixed mass of gas at a constant volume, pressure is proportional to temperature
Derive Boltzmann equation from ideal gas equation
Define pressure and state equation linked
Pressure is normal force per unit surface area over which the force acts
Pressure = force / area
State use of equation that links work done, pressure and volume
Energy needed/ released is area under graph
In molecular kinetic theory, state what happens when molecules hits wall of container
What are the 5 ideal gas laws in molecular kinetic theory
- Total volume of each molecule is negligible compared to the total volume of the gas
- The intermolecular forces between molecules are negligible
- Time between collisions with container walls and other molecules is much greater than the duration of collisions
- Collisions between container walls and other molecules are considered elastic
- There are a large number of molecules who’s motion is random
What is Brownian motion
When particles are inserted into something, particles are moving randomly
E.g if you have dust particles suspended in a gas, gas molecules collide with dust particles and gas particles start moving randoml
What does average velocity equal to
Crms
Start with square, then mean, then square root
How do you calculate total kinetic energy of a gas
Number of molecules x average kinetic energy of a molecule
What is internal energy
Define specific heat capacity
Specific heat capacity is energy needed to raise temperature of 1kg of a substance by 1 Kelvin
Define thermal equilbrium
Two objects are in thermal equilbrium if there is no net energy transfer between them when they are placed in contact
When two objects off current temperatures are placed into contact, how do they reach thermal equilbrium
How else can you write Q=mc x delta t, get rid of Q
P is power not pressure
Define specific latent heat of fusion
Energy required to change 1kg of a substance from a solid to a liquid at its melting point
Define specific latent heat of vaporization
Energy required to change 1kg of a substance from a liquid to a gas at its boiling point
Define the Avogadro constant
Number of atoms in 12 grams of carbon-12
State units of mean square speed
m^2 s^-2
Outline what is meant by an ideal gas
Must use 3RT/2Na as they contain all constants apart from temperature
Temperature = 320 Kelvin
B
A
I = p/v gives 19.6 A
Current required for 4.5 kW would exceed fuse rating
Kinetic energy is exchanged in molecular collisions
Until average kinetic energy of all molecules is the same
Curve A below original
Curve B above original
An assumption is that molecules are in a state of random motion. What is meant by random motion
Molecules have a range of speeds
They have no preferred direction of movement
Skip calculation part, as long as you get equation needed correct
Just do biii) using the table
Temperature is proportional to kinetic energy
At 0 Kelvin, kinetic energy would be zero
As there would be a straight line through the origin
Assumptions made when estimating time it takes for water to turn into ice
Constant rate of heat loss
Ice remains at zero degrees
Ice requires energy to melt
Stays at zero degrees for longer and cools for longer
Two cylinders require exact amount of energy to raise the temperature but one has molecules with greater mass. Explain why they require exact amount of energy
As they have same number of molecules and same increase in average kinetic energy
Explain why average velocity of gas molecules in a container is zero
Velocity is a vector
Random velocity means no preferred direction of movement
Velocities cancel out
Gas undergoes a change from A to B. Volume at A is 0.7 x 10^-3 m^3 and pressure at A is 10^5 Pa and temperature at A is 27 degrees. Volume at B is 0.5 x 10^-3 m^3 and pressure at A is 10^5 Pa. Calculate change in temperature from A to B
Use VA/TA = VB/TB
However you got it wrong Because you need to say MINUS 86, remember final temp is lower so must be a minus
Compare work done on gas during change of A to B with that of B to C
