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3
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The degree to which the particles move is
determined by the amount of energy they have and their relationship to other particles
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Use of the general term 'particle' means the
precise nature of the particles does not have to be specified
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As a model it is useful because it appears to explain many phenomena but as with all models it does have limitations
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2) The number of molecules is very large but their separation is large compared to their molecule size
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4) Molecules undergo elastic collisions with each other and the walls of the container but otherwise exert no forces on each other
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Kinetic theory is based on four key

Thermal energy is the net disordered kinetic energy possessed by the group of particles that constitute a sample of bulk matter
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) to directly impart thermal energy to a
thermometer, or any other object
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Temperature = Internal
energy/number of particles
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A body contains or stores thermal energy not heat
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Temperature and absolute temperature
Since the addition of thermal energy (heat) causes materials to expand, a thermometer can
be used to measure temperature
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The lowest pressure p that can exist is zero
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This temperature is called absolute zero
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To convert between
Celsius and Kelvin, add 273 to a Celsius temperature
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When a substance is heated up there is an increase in the potential energy and kinetic energy of the substance
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The amount of thermal energy required to change the temperature of water is proportional to the total temperature change
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Specific heat capacity
Heat energy is normally measured in calories:
1 calorie is the amount of heat needed for 1 gram of water to be increased by 1 C°
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186 kJ (mechanical equivalent of heat)

Specific heat capacity definition:
The specific heat capacity is the amount of heat per unit mass needed to raise the
temperature by one degree Celsius
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The higher the specific heat capacity, the longer it takes to heat something up
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The intermolecular forces between the ______ molecules are decreasing/increasing
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Solid > Liquid > Gas
Decreasing intermolecular forces

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Interpreting phase change graphs
A phase diagram summarises the relationships between the solid, liquid and gaseous states of a substance
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The triple point is when a substance is at the pressure and temperature where all three phases of the
substance coexist within thermodynamic equilibrium
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Latent heat means hidden heat
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(When changing from solid to liquid or vice versa)
is the latent heat of vaporization
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2 - Modelling a gas

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Pressure
The molecule is accelerating
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The walls of the box feel a pressure
Pressure is in the units pascal (Pa)
Pressure is force divided by area

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Kinetic model of an ideal gas
• An ideal gas is an imaginary gas that is used to model real gases, and has the following
properties:

• If the temperature of a gas increases, so does the average speed (and hence kinetic
energy) of the molecules
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• In a smaller volume the molecules have less distance to travel to hit a wall
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Thus the pressure will be bigger if the volume is smaller
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Real gases are not identical perfect spheres
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They do
not lose energy when they collide with
each other
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Ideal gases have no intermolecular forces
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Ideal gases are small
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Gas Laws
Work = pressure times change in volume

Boyles Law
Constant Temperature
Charles Law
Constant Pressure
GayLussac Law
Constant Volume

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The Avogadro constant
The Avogadro's constant is:
the number of molecules in one mole of a substance
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The molar mass is the mass of a given chemical element or chemical compound (g) divided
by the amount of substance (mol)
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31 J/Mol K (Universal gas constant)
If there are two valves:

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Questions

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