Good Science Victorian Curriculum Year 7

CHAPTER 5: MIXTURES
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Solutions are solutes in solvent
A solution is a mixture made up one or more solutes dissolved in
a solvent. A cup of black coffee, for example, is a solution made up of:
• solutes – powdered coffee and perhaps sugar
• a solvent – water.
Any solution that has water as a solvent is called an aqueous solution.
What is a solution made up of?
Solutions, suspensions and colloids
Not all solutions are the same. Different solutes make different solutions.
Also, the amount of solute affects the solution.
• Concentrated solution: a solution with a lot of solute. Putting
20 tablespoons of cordial in one glass of water gives you a
concentrated (and unpleasantly sweet) solution.
• Dilute solution: a solution with a very small amount of solute.
Putting a quarter of a teaspoon of cordial in a large glass of water
makes a dilute (and not sweet enough) solution.
Suspensions and colloids contain particles that behave differently
to those in solutions.
• Suspension: a mixture with large, insoluble particles that are spread
out evenly at first and eventually settle to the bottom. A snow globe,
with a mixture of plastic ‘snow’ particles and water, is a suspension.
• Colloid: a mixture with tiny particles spread out evenly that never
settle to the bottom. Milk is a colloid because it contains tiny droplets
of fat in water.
How do particles in a suspension
behave differently to those
in a colloid?
Figure 5.4
The liquid in a snow
globe is a suspension of
plastic particles in water.
INVESTIGATION 5.2
The Tyndall effect
KEY SKILL
Identifying the
variables and
formulating a hypothesis
Go to page 154
CHECKPOINT 5.2
1 Name three solutes.
2 For each of the three solutes
above, identify a possible
solvent.
3 Describe the difference
between a solution and a
solvent.
4 Copy and complete this
sentence. A solution is a
dissolved in a .
5 What is the difference between
a concentrated solution and a
dilute solution?
6 In each of these aqueous
solutions, identify the solute
and the solvent.
a A cup of sweet, black tea
b A glass of orange juice made
from powdered concentrate
c Sea water
7 A substance is added to
a beaker of water. Initially
the substance makes the
water blue and cloudy. The
substance then settles at the
bottom of the glass. What type
of mixture is described here?
CONNECTING IDEAS
8 Do you think that fog is
an example of a colloid?
Justify your answer.
SUCCESS CRITERIA
I can describe solutes,
solvents and solutions in
my own words.
I can give an example of a
solute, solvent and solution.
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