Good Science Victorian Curriculum Year 7

CHEMICAL SCIENCES
5.1
MIXTURES
AND PURE
SUBSTANCES
LEARNING INTENTION
At the end of this lesson I will be
able to explain what a mixture is
and why it is important to be able
to separate mixtures.
KEY TERMS
mixture
a substance that is composed
of different types of particles,
all mixed together
ore
a rock found in nature that
contains metal
pure substance
a substance that is composed
of only one type of particle
1
A pizza is a combination of different things. There’s the crust,
the meat (or other toppings) and the cheese. Each of these
ingredients is a mixture as well: the crust is made of flour,
yeast and water; the meat is made of protein, fat and water;
and the cheese is made of protein and fat. All substances
can be classified according to what they are made up of –
a substance such as water that contains only one type of
particle is called a pure substance. Other substances that
contain combinations of other things are called mixtures.
To tell the difference, we need to know what a substance is
made up of at the particle level.
Pure substances contain only one type
of particle
All substances are made up of particles. Some substances, such as
sand, are made of particles that are easy to see. Some, such as water,
are made of particles that are far too small to see with the naked eye.
In a pure substance, all of the particles it contains are exactly the
same. If you took a very powerful microscope and looked at pure water,
you would see that every particle in the water is identical.
Other examples of pure substances are oil, salt, iron and diamond.
Combining two or more pure substances will usually create a mixture.
What is a pure substance?
LITERACY LINK
SPEAKING
Think of a mixture. A partner then
has to try and guess what your
mixture is by asking a maximum
of 20 ‘yes’ or ‘no’ questions.
NUMERACY LINK
CALCULATION
A bottle of cordial suggests
adding one part cordial to five
parts water. How much cordial
would you need to make 2.4 litres
of cordial solution?
pure pure substance substance pure pure substance substance mixture
mixture
Figure 5.1 The particles in a pure substance are all the
same. Combining two pure substances will form a
mixture, where the particles are no longer all identical.
68 GOOD SCIENCE VICTORIAN CURRICULUM 7