# Thermal Physics

• Created by: dkoning00
• Created on: 01-06-18 11:49
Define internal energy
The sum of the random potential and kinetic energies of the molecules in a system
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What causes potential energy?
The forces acting between molecules
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What causes kinetic energy?
Molecular motion
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Define specific heat capacity
The amount of energy needed to raise the temperature of 1kg of a substance by 1K without changing its state
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What type of energy flows into or out of the system when temperature changes?
Kinetic energy
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Define the specific latent heat of fusion
The energy require to change 1kg of a substance from solid to liquid without changing its temperature
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Define the specific latent heat of vapourisation
The energy required to change 1kg of a substance from liquid to gas without changing its temperature
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What type of energy is changing during change of state and why?
Potential energy from bonds forming or breaking between the molecules
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State Boyle's Law
For a fixed mass of an ideal gas at a constant temperature the volume of a gas is inversely proportional to the pressure
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Describe an experiment to show Boyle's Law
Using a tube of constant cross-sectional area partially filled with oil, increase pressure using a pump and take periodic measurements of the height of the oil. From this plot a graph of P against 1/L, should be a straight line through origin
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Describe how a syringe draws liquid
Pulling the plunger increases volume in the chamber, this decreases pressure in it and so the pressure on the liquid from the air outside is greater than in the syringe so liquid is driven into the chamber
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State Charles' Law
For a fixed mass of an ideal gas at constant pressure, the volume of a gas is directly proportional to the absolute temperature
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Describe how you would show Charles' Law
By heating a column of water with constant cross-sectional area at constant pressure and taking periodic measurements of the height of the water at certain temperatures and plotting V against T, will show a straight line passing thru. absolute 0
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State the Pressure Law (Gay-Lussac Law)
For a fixed mass of an ideal gas at constant volume the pressure of a gas is directly proportional to the absolute temperature
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Describe the apparatus needed to demonstrate the Gay-Lussac Law
A sealed vessel of a known volume of air attached to a pressure gauge sitting in a heated water bath with a thermometer
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Combining the three laws, give an equation linking the pressures, volumes and temperatures of two ideal gases
(p1V1)/T1 = (p2V2)/T2
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State the ideal gas equation and meaning of each part with units
pV=NkT p-pressure in Pascals V-volume in m^3 N-number of molecules of gas k-Boltzmann constant T-absolute temp in Kelvin
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State the five assumptions we make about the molecules when relating the microscopic behaviour of gas particles
1.Continuous state of random motion 2.exert no forces on each other 3.collisions between molecules and container are elastic 4.duration of collisions is negligible compared to time between them 5.vol. of molecules is negligible compared to container
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Using kinetic theory describe how an air hockey table works
Air molecules moving up have elastic collisions with puck causing downwards impulse. Newton 2 states there is a downwards force on the molecules, therefore there is an equal upwards force on the puck (Newton 3). Net upward force balances weight
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How can it be shown that the kinetic energy of molecules of gas depend solely on the termperature
pV=(3/2)kT pV=1/3)Nm two equations for pressure times volume
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What two measurements need to be taken to find the root mean square speed of a molecule of a given gas?
pressure and density
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## Other cards in this set

### Card 2

#### Front

What causes potential energy?

#### Back

The forces acting between molecules

### Card 3

#### Front

What causes kinetic energy?

### Card 4

#### Front

Define specific heat capacity

### Card 5

#### Front

What type of energy flows into or out of the system when temperature changes?