GCSE: Physics, module P1
Topic One:
P1.1.2 The Kinetic Theory
How are solids, liquids and gases different?
How are the particles in a solid, a liquid and a gas arranged?
Why is gas much less dense than a solid or a liquid?
The three states of matter
Solid
Liquid
Gas
Flow
Shape
Volume
Density
No
Fixed
Fixed
High
Yes
Fits container
Fixed
Medium
Can be changed
Low
Yes
Fits container shape
melting
freezing
Liquid
evaporation
Materials can change from one state to another when the temperature changes:
condensation
Solid
Gas
actual water vapour is colourless
This cloud is made up of tiny droplets of liquid water which form when the steam/water vapour condenses
Colourless, transparent water vapour condenses back into liquid water on chilly surfaces
States of matter practical
Hazard:
Boiling water
notice what happens to the test tube
ev
condensation
ap
melting
ora
tio
n
boiling water
What is heat?
Heat is the vibration of the atoms of a substance.
The hotter the material, the more the atoms vibrate.
Notice that the material expands, but the atoms stay the same size.
The atoms gain kinetic (movement) energy
The three states of matter
o
• Atoms are always vibrating, even at absolute zero (­273 C)
• increasing the temperature makes the atoms vibrate more
• but the bonds between them always stay the same strength
solid
The bonds hold the atoms in a fixed shape
liquid
The atoms are still held
­but not in a fixed arrangement
gas
The bonds can no longer hold the atoms
Methane can be a gas, a liquid
or a solid.
In the diagram below, arrows
P, Q, R and S represent
changes of state.
The boxes on the right show
the arrangement of particles
of methane in the three
different physical states.
Each circle represents a
particle of methane
(i)
Draw a line from each
physical state of methane to
the arrangement of particles
in that physical state.
Draw only three lines.
1 mark
(ii) Arrows P, Q, R and S represent changes of
state.
Which arrow represents:
P
evaporation? ............................................................
R
melting? ...................................................................
2 marks
Key Points
Flow, shape, volume and density are the properties used to describe each state of matter
The particles in a solid are held next to each other in fixed positions
The particles in a liquid move about at random and are in contact with each other The particles in a gas move about randomly and are much further apart than particles in a solid or in a liquid