1. S.7 Dissolving
and Crystalizing
Solutions.
How solids become liquids
and solids again……….
Surf Coast Secondary College

2. What is a Solid?
A solid is a substance that is
considered to be structurally
rigid and resistant to changes
in shape and volume.
However there are some
exceptions. Sand for example
is considered a solid but can
be poured like a liquid.
 A solid substance contains Particles
particles that are closely
packed together.

3. What is a liquid?
A liquid is a substance that
has a definite volume that
has no fixed shape.
 A liquid is made up of tiny
particles that are able to
freely move. Unlike gas they
do not inhabit the whole
space it is in as it has a Particles
relatively fixed volume.

4. Combining Solids and Liquids
 Liquids and solids can be combined and
depending on the substance the solid may
dissolve into the liquid forming a solution.
 A solvent is a substance, usually a liquid, that
will dissolve another substance.
 The substance that dissolves in a solvent is
called the ‘solute’.
 Together, the solvent and the solute make up
a mixture called a ‘solution’.

5. Heating Salt water
 Heating salt water reveals the solute in sea water.
 Watch the following video and answer the
questions.
 Where does the water go and why?
 What is left?
 Note the size of the crystals.

6. Salt water and liquid copper
sulphate are solutions!
Solute Solvent Solution
Water (H2O) Salt (+ some other Salt water (Sea
elements) water)
Water (H2O) Copper Sulphate Liquid Copper
(CuSO4) Sulphate
Complete the following in your lab
books and post to Posterous when
complete.

7. Procedure (READ before
completing the task)
 You are to take 1 x petri dish (top
& bottom). Write your name on
the side in permanent marker.
 On the other side write the name
of the solution, i.e. salt water &
copper sulphate.
 Pour 15ml of each solution into
the corresponding dish.
 Take a photo of each dish and
place the dishes into the tub to
be put into the store room over
the weekend.

8. Think about it. Predicting.
 What do you think will happen to the
solutions?
 What will the differences be between the
two solutions after 3 days?
 Write
a hypothesis (educated prediction
to describe what you think is going to
happen.

9. Observation.
 Once you have your petri dishes back
describe what they look like.
 Take a picture of each dish, and describe
each one.
 Is there any significant
differences/similarities between the two
dishes?
 Was your hypothesis proven? Discuss.
 Post to Posterous.