# Thermal physics notes - PHYA5

Summarised notes of chapter 11.

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• Created by: glow.
• Created on: 02-03-13 11:09

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Thermal physics
Energy transfer happens when:
One object does work on the other one
Energy transfer due to a temperature difference
Internal energy of object changes as result of:
Work done by force or electricity on/ by object
If internal energy constant, either:
No heat/ energy transfer by radiation and no work done
Heat/ energy transfer by radiation and work done BALANCE each other out
Heat: solids ­ molecules vibrate
forces. May break with enough KE
supplied which raises PE of
molecules.
Liquids ­ forces not strong enough
to hold molecules in fixed
positions. More energy supplied
to raise temp = increase KE
molecules = vaporisation
Gas ­ almost no forces of
attraction between moleucles ­
high speeds ­ collisions with
container responsible for pressure
which gas exerts on container.

## Other pages in this set

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Fixed points: standard
degrees of hotness which
can be accurately
produced:
Celsius scale
ICE POINT ­ 0' ­ pure melting ice
STEAM POINT ­ 100' ­ steam at standard atmospheric pressure
Absolute scale
ABSOLUTE ZERO ­ 0K ­lowest possible temp.
TRIPLE POINT OF WATER ­ 273.16K - temp which ice water and water vapour are in thermal
equilibrium
An object at absolute zero has minimum internal energy.…read more

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The temperature rise of an object when it's heated depends on:
Mass
Amount of energy supplied to it
Q = M C T
Inversion tube experiment
GPE internal energy when it hits bottom. Little spheres in tube carry

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Metal
Electrical energy supplied: IVt
M C T = I V T
Liquid:
known mass in insulated calorimeter.…read more

### Page 5

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The three physical states of a substance have different physical properties:
Density of gas much less than liquid or solid because liquid/solid molecules compact and in
contact with each other. Molecules of gas separated by large distances.
Solids cant flow because there atoms are locked together by strong force bonds which
atoms unable to break from. Liquids/ gases have too much KE and bonds can't keep

### Page 6

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Q = ml
Where l is latent hear of fusion/ vaporisation ( Jkg^-1)…read more