1. Variables in Science

2. Objectives: Students will be able to identify:
The independent variable
The dependent variable
The controlled variable or constants in an experiment

3. Variables are things that vary and change.
What are variables?
Variables are things that vary and change.

4. 3 Types of Variables In an experiment there are 3 variables:
An independent variable
A dependent variable
Controlled variables that are sometimes called constants
Let’s look at each type.

5. I change Independent Variable Think Independent = I change
The independent variable is the part of the experiment that you decide to change.
Think Independent = I change
I change

6. For example:
An experiment testing to see if temperature of water effects the amount of sugar that will dissolve
Ask - what am I changing?
You would change the temperature of the water
Water temperature is the independent variable

7. Another example:
An experiment testing the effect of different amounts of fertilizer on plant height
Ask - what am I changing?
You would change the amount of fertilizer
The amount of fertilizer is the independent variable

8. Dependent Variable
The dependent variable changes because of the independent variable.
The dependent variable is what is measured in the experiment.
Think Dependent Variable = Data
What is the data you are collecting in the experiment? What is being measured?

9. For example:
An experiment testing to see if temperature of water effects the amount of sugar that will dissolve
Ask – what is the data?
You would collect data on the amount of sugar that dissolves
The amount of sugar is the dependent variable

10. Another example:
An experiment testing the effect of different amounts of fertilizer on plant height
Ask - what is the data?
You would collect data about the height of the plant
The plant height is the dependent variable

11. Controlled Variables or Constants
Controlled variables or constants are the parts of the experiment that must stay the same.
The controlled variables make the experiment a fair test.
Think of controlled variables as the unchanging parts of the experiment.
Think constant = No Change
change

12. For example:
An experiment testing to see if temperature of water effects the amount of sugar that will dissolve
Ask – what must stay the same to be fair?
Same container, same amount of water, same type of sugar

13. Another example:
An experiment testing the effect of different amounts of fertilizer on plant height
Ask – what must stay the same to be fair?
Same fertilizer brand, same type of plant, same measurement standard, same amount of water and light

14. Your turn:
A test to determine which type of ball (golf, basketball, ping pong, or tennis) bounces the highest when dropped
What is the independent variable?
What is the dependent variable?
What are some of the controlled variables or constants?
Discuss your answer with your shoulder partner.

15. Answers Independent variable = I change The type of ball
Dependent variable = data
The height of the bounce
Controlled variable or constants = no change for a fair test
All balls must be dropped from the same height in the same way

16. Graphing When graphing the data, think -
DRY MIX – the Dependent variable goes on the Y axis and the Independent variable goes on the X axis
Dry -
dependent
Mix - independent

17. No monkey-ing around!
You are ready to identify variables.