STATES OF MATTER -
properties of gases and liquids (fluids) and solids
Introduction to the three states of matter
chemistry revision notes: basic school chemistry science GCSE chemistry, IGCSE chemistry, O level
and ~US grades 8, 9 and 10 school science courses or equivalent for ~14-16 year old
science students for national examinations in chemistry and also helpful for UK
advanced level chemistry students aged ~16-18 and US grades 11-12 K12 honors.
Part 1 Introduction to
the three states of matter
You should know that the three states of matter are solid, liquid and gas.
Melting and freezing take place at the melting point,
boiling and condensing take place at the boiling
point. The three states of matter can be represented by a
simple model in which the particles are
represented by small solid spheres. Particle theory
can help to explain melting, boiling, freezing and
The amount of energy needed to change state from
solid to liquid and from liquid to gas depends on the
strength of the forces between the particles of the
substance and the nature of the particles involved
depends on the type of bonding and the structure of
the substance. The stronger the forces between the
particles the higher the melting point and boiling
point of the substance.
of latent heat changes in physical changes of state for different types of
for more details see
structure and bonding
The strength of the forces between particles
depends on the material (structure and type of bonding), the temperature
(affects the energy of the particles) and pressure (how close the particles are
compressed together e.g. in a gas).
The physical state a material adopts
depends on its structure, temperature and pressure.
State symbols used in equations:
gas (l) liquid
(aq) aqueous solution (s) solid
aqueous solution means something dissolved
a good example of how to use the state
symbols correctly is calcium carbonate dissolving in hydrochloric acid:
2HCl(aq) ====> CaCl2(aq) +
H2O(l) + CO2(g)
diagrams of particles are often 2D representations of their structure
EXAMPLES OF THE THREE PHYSICAL STATES OF
e.g. the air
mixture around us (including the oxygen needed for combustion) and the high
pressure steam in the boiler and cylinders of the steam locomotive. All of
the gases in air are 'invisible', being colourless and transparent. Note that
the 'steam' you see outside of a kettle or steam locomotive is actually fine liquid
droplets of water, formed from the expelled steam gas condensing when it
meets the cold air – the 'state change' of gas to liquid (same effect in
mist and fog formation).
e.g. water is the
most common example, but so are, milk, hot butter, petrol, oil, mercury or
alcohol in a thermometer.
e.g. stone, all metals
at room temperature (except mercury), rubber of walking boots and the majority of physical
objects around you. In fact most objects are useless unless they have a
The basic physical properties of gases,
liquids and solids are described in terms of structure, particle movement
(kinetic particle theory),
effects of temperature and pressure changes, and particle models used to explain these
properties and characteristics. Hopefully, theory and fact will match up to give students a clear
understanding of the material world around them in terms of gases, liquids and
solids – referred to as the three physical states of matter.
The changes of
state known as melting, fusing, boiling, evaporating, condensing, liquefying,
freezing, solidifying, crystallising are described and explained with particle
model pictures to help understanding. There is also a mention of miscible and
immiscible liquids and explaining the terms volatile and volatility when applied
to a liquid.
Some SIMPLE particle
pictures of ELEMENTS, COMPOUNDS and MIXTURES in terms of the three states of
Learning objectives for
particle pictures and
an introduction to the states of matter
Know that matter can exist in a solid, liquid and gaseous state and
recognise the state from a given description or picture of a material.
Be able to recognise from particle pictures whether the substance is a
solid, liquid or gas and also deduce whether it is a particle picture of a pure element,
a pure compound or
a mixture of elements or compounds.
UK GCSE level (~US grade 8-10) school chemistry revision
All my UK advanced level (~US grades 11-12)
pre-university chemistry revision notes
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INDEX of all my notes on the states of matter
(GCSE level and advanced pre-university level
notes on the states of matter and their properties