1. Lessons 2 & 3: variables, tables and graphs
How science works
Lessons 2 & 3: variables, tables and graphs

2. Learning objectives
We are learning to:- Identify variables and use them to make a table and plot a graph What I’m looking for:- You must be able to draw a simple table to record the results of an experiment (grade E) You should be able to identify the control, independent and dependent variables in an experiment (grade C) You could be able to plot a line graph of your results (grade B)

3. variables
Variables – these are all the factors that could have an effect on the investigation Control variables – these are the most important variables that should be considered, they usually need to be controlled (kept constant) to have fair test Independent variable – this the ‘input factor’ you will be changing and testing Dependant variable – this is the variable you measure that depends on the independent variable.

4. Check your learning: 1
Complete Task 1 on your worksheet: Using 2 different colours, highlight the independent and the dependent variables in the 9 investigation aims listed.

5. basic theory of hooke’s law
When a force is exerted on a spring it will either compress (push the spring together) or stretch the spring if the weight is hung on it.

6. investigation
An investigation into how the amount of mass affects the extension of a spring
In this experiment the extension of the spring is measured with increasing weights being added 1N, 2N, 3N to 5N.
The extension is a measure of how much the spring stretched. (Not the total length of the spring)

7. Independent variable Dependent variable Control variable
Mass (g) going up in 100 grams
Dependent variable
Extension (cm)
Control variable
Forcemeter, spring, same set of masses.

8. Always use squared or ruled paper Always use a ruler
How to draw a good table
Always use squared or ruled paper
Always use a ruler
The independent variable goes in the first column
The dependent variable goes in the next column
Always have 3 repeat columns or tables
Always have an average
Always round up your results (more on this soon!)

9. Results of Experiments
Mass in g
extension of spring (cm)
Try 1
Try 2
Average extension of spring (cm)
100
200
300
400
500

10. Results of Experiments
Mass in g
extension of spring (cm)
Try 1
Try 2
Average extension of spring (cm)
100 4 5 3
200 8 7 9
300 12
400 16 15 17
500 20 19 22

11. How to plot a good graph Always use graph paper
Always use a sharp pencil
Make certain that the independent variable is on the x axis and the dependent variable is on the y axis
Have a suitable scale that fills the whole paper
Plot carefully putting an ‘x’ at each point
Join the points together using a ruler or a smooth curve. DO NOT DO DOT TO DOT!!!