What are Variables?
These factors that change in a scientific experiment are variables.
What is an Independent Variable?
The independent variable(s) is the one that is changed by the scientist. Why just one? Well, if you changed more than one variable it would be hard to figure out which change is causing what you observe.
What is an Dependent Variable?
The dependent variables are the things that the scientist focuses his or her observations on to see how they respond to the change made to the independent variable.
What is an Controlled Variable?
Experiments also have controlled variables. Controlled variables are quantities and factors that a scientist wants to remain constant in order to make the experiment fair, and she or he must observe them as carefully as the dependent variables.
| Question | Independent Variable (What I change) | Dependent Variables (What I observe) | Controlled Variables (What I keep the same) | |
|---|---|---|---|---|
| Does heating water allow it to dissolve more sugar? | Temperature of the water measured in degrees Celsius | Amount of sugar that dissolves completely, measured in grams | - Stirring - Type of sugar | |
| How fast does a candle burn? | Time measured, in minutes | Height of candle, measured in centimeters, at regular intervals of time (for example, every 5 minutes) | - Use same type of candle for every test - Make sure there isn’t any wind | |
| Does an electric motor turn faster if you increase the voltage? | Voltage of the electricity, measured in volts | Speed of rotation, measured in revolutions per minute (RPMs) | - Same motor for every test - The motor should be doing the same work for each test (turning the same wheel, propeller, or whatever) |
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