1. Natural Sciences Grade 7
Term 3: Energy and Change
Heat transfer

2. Natural Sciences - Grade 7
Topic 3 Heat transfer
Variables
Natural Sciences - Grade 7

3. Natural Sciences - Grade 7
What are variables
Things that change in an investigation, are called variables.
It is measurable.
It can be seen / observed.
During an investigation you only select one variable to change, while the other variables are all kept the same.
Examples: time; amount of substance that is used; temperature; type of material used and mass.
Natural Sciences - Grade 7

4. Natural Sciences - Grade 7
Two types of variables
Dependent variable
It is also called the output variable.
It is the variable that changes in response to the independent variable that is being changed.
It is also the thing that you observe or measure and the experiment’s result.
Natural Sciences - Grade 7

5. Natural Sciences - Grade 7
Two types of variables
Independent variable
It is also called the input variable.
It is the variable that you change when you conduct an investigation [e.g. using 2 cups of water, instead of 1 cup].
Natural Sciences - Grade 7

6. Natural Sciences - Grade 7
Variables continued
Example: How long does it take to boil one cup of
water? (see picture on next slide)
the independent variable is the cup of water.
the dependent variable is the time that we measure.
a fixed / controlled variable can be keeping the stove on high; medium and low.
Natural Sciences - Grade 7

7. Example: boiling 1 cup of water
independent variable
= cup of water in kettle
dependent variable
= time that we measure
controlled variable
= heat of the stove:
low, medium or high
Natural Sciences - Grade 7

8. Natural Sciences - Grade 7
Variables continued
The independent variable can be changed by using two cups of water and we can now again measure the independent variable by using two cups of water to boil.
The stove setting is still on high, therefore the controlled variable stays the same.
Natural Sciences - Grade 7