As an adult and a scientist, I can’t tell you how humbling it is to need to be reminded what the difference is between “Independent and Dependent” variables, and yet each year during science fair preparation, I have to remind myself so that I can best help my child understand. At its very core, a science fair project is testing “cause and effect”. It is common for children to want to “demonstrate” something, like the ever popular baking soda volcano. This however is not a science fair project on its own but needs to answer some question related to the volcano. For example, what would happen to the volcano if you alter the amount of baking soda you use, will the explosion be bigger or smaller. What if you change the vinegar to lemon juice or water?
This type of questioning introduces variables. A variable is any factor, trait, or condition that can exist in differing amounts or types. An experiment usually has three kinds of variables: independent, dependent, and controlled. The independent variable is the one that you change. It is best to change only one thing as you conduct your experiment. In the volcano example, the liquid you change to initiate the reaction is the independent variable. Keeping the amount of baking soda, temperature of the room and volcano structure exactly the same, allows the changing observations to be tied directly to the liquid being tested.
The dependent variable is the change that you observe in response to the independent variable. In our example, the dependent variable is the change in the “lava” created in the experiment. The key to a good experiment is being able to measure the change. This might not be easy in our volcano experiment. So when helping your child design their experiment, help them think through how to measure results. Could you use a scale, thermometer, count the result in some way? Observations are also ways to document a change, but ensure that you document the observation in some way, such as photographs.
Lastly, the controlled variables are the things that do not change in the experiment such as the amount of baking soda, the rooms temperature or the use of the same volcano for all experimental runs.
The Crofton Elementary School Science Fair will be held February 21, 2013. Check out our Science Fair page for more information and the link to our online sign up form. Sign up for your science fair project by February 8, 2013.