Good Science Victorian Curriculum Year 7

INVESTIGATIONS
Investigation 5.6B
Growing crystals
KEY SKILL
IDENTIFYING THE VARIABLES AND
FORMULATING A HYPOTHESIS
Before you formulate a hypothesis, identify your
independent, dependent and controlled variables.
The independent variable is the one thing that you
purposefully want to change in an investigation.
The dependent variable is what you will be measuring.
The controlled variables are all the things you need
to keep the same throughout the investigation.
To formulate your hypothesis use the following
sentence stem: It can be hypothesised that if (something
to do with your independent variable), then (something to
do with your dependent variable).
Hint #1: If you get stuck, use the prompts in Lesson 1.4
to help you.
AIM
To investigate growing crystals at different
temperatures
MATERIALS
• electronic balance
• 30 g of copper sulfate (solid)
• 2 × 100 mL beakers
• hot water from tap
• 2 stirring rods
• cotton
• 2 paperclips
30 min
METHOD
1 Add 30 g of copper sulfate to a beaker containing
40 mL of hot water. Stir with a stirring rod until the
solid dissolves.
2 Pour half of the volume into another beaker. Cool this
beaker by running cold water on the outside.
3 Tie a piece of cotton to each stirring rod and attach
a paperclip at the other end. Hang the strings with
paperclips inside each beaker.
4 Leave the beakers for several days to allow crystals
to grow.
5 Describe what you can see inside each beaker.
QUESTIONS
1 Compare the sizes of the crystals in the two beakers.
How could you make the crystals bigger?
2 Identify the independent, dependent and controlled
variables.
3 Use the variables identified above to write a
hypothesis.
4 Was your hypothesis supported (correct) or rejected
(incorrect)?
CONCLUSION
Copy and complete:
‘The results show that: (respond to the aim)’.
Level 1
160 GOOD SCIENCE VICTORIAN CURRICULUM 7