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13 Matter: very simple



Revision Guide for Chapter 13
Contents
Student's Checklist

Revision Notes
Ideal gas .................................................................................................................................... 4
Ideal gas laws ............................................................................................................................ 4
Assumptions of kinetic theory of gases ..................................................................................... 5
Internal energy........................................................................................................................... 6
Specific thermal capacity........................................................................................................... 6
Conservation of energy ............................................................................................................. 7
Absolute temperature ................................................................................................................ 7
Root mean square…

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13 Matter: very simple



Student's Checklist
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I can show my understanding of effects, ideas and
relationships by describing and explaining cases involving:

the behaviour of ideal gases

Revision Notes: Ideal gas; Ideal gas laws;
Summary Diagrams: Boyle's law, density and number of molecules; Change of…

Page 3

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13 Matter: very simple


I can sketch, plot and interpret:

graphs showing relationships between p, V and T for an ideal gas

Revision Notes: Ideal gas laws;
Summary Diagrams: Change of pressure and volume with temperature; Ideal gas laws in
pictures


I can make calculations and estimates involving:

the universal…

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13 Matter: very simple




Revision Notes
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Ideal gas
An ideal gas is an abstraction from the fact that many real gases have closely similar
behaviour, in particular that the ratio p V / n T is very nearly the same for all of them at…

Page 5

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13 Matter: very simple

V

P1>P2


P2




O T
Charles' law

The pressure law: p / T = constant for constant n and V.

P
V1>V2


V2




O T
The pressure law

These laws can be combined into the general ideal gas law
pV =NkT where N is the number…

Page 6

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13 Matter: very simple

The kinetic theory gives, for the pressure p of volume V of an ideal gas:
pV = 1
3
Nm c 2 .
where:
N is the number of molecules
m is the mass of a molecule
c 2 is the mean of the squares of…

Page 7

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13 Matter: very simple


Conservation of energy
Imagine a closed boundary drawn around any set of objects, large or small. In a given time,
energy may enter across the boundary and energy may leave across the boundary. The
Principle of Conservation of Energy states that the change in energy within…

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13 Matter: very simple


Root mean square speed
The speeds of molecules in a gas vary around an average value. The distribution of speeds of
molecules in nitrogen at 300 K is shown below.

mean speed
most probable root mean
speed square speed
0.10


0.08


0.06


0.04


0.02


0.00




speed…

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13 Matter: very simple



Summary Diagrams (OHTs)
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Boyle's law, density and number of molecules

Boyle's law and gas density
1 2 pressure p
4 3




volume V
mass m
density d




Boyle's law:
compress gas to half volume: half as much gas in half volume:…

Page 10

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13 Matter: very simple


Boyle's law and number of molecules


Two ways to double gas
pressure



molecules in box:
pressure due to impacts
N molecules in volume V of molecules with walls
of box
squash the gas cram in more molecules
decrease V increase N


piston squashes up same molecules…

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