Scientific Method: Easy Contests to Teach Students About Fair Tests

In my experience, many elementary students struggle to grasp the idea of controlled variables (constants) and why they are important for fair tests.

What have my students always had an understanding of?  Fairness in a game.

I have an easy, fun idea to share with you that may help your students better understand the need to have a fair test and what their variables are.

The Drag Race

Materials: small ramp, 2 different toy cars

1. Divide your class in half, Team 1 and Team 2.

Red Car vs. Black Car

2. Explain that you’re going to have a contest to see which car can roll farther down a ramp. BUT, there’s a catch.  Team 1 can push the red car from the top of the ramp.  Team 2 has to gently release the black car from the middle of the ramp.

3. Hear them grumble about fairness but hold the contest anyway.

4. Discuss.  What wasn’t fair?  Were there too many variables?  What would make it more fair?   Should both teams gently release the car from the same spot at the top of the ramp?

5. Try it again, this time as a fair test controlling for outside variables.

6.  Talk about it.  What was the one thing that was different (independent variable) in this contest? (the car)  What was the same?  (the ramp, where the car was released, the power with which the car was released, the surface at the end of the ramp)

The Chocolate Melt

Materials: 2 white chocolate Kisses or Hugs, 2 milk chocolate Hershey Kisses, 4 plastic cups

1. Stay in your teams, Team 1 and Team 2.

Hug vs. Kiss

2. You’re going to have another contest.  This time you want to know whose Hershey Kiss can stay solid the longest.  Again, there is a catch.  Team 1 keeps their white chocolate or Hugs under a desk lamp.   Team 2 puts their Hershey Kiss in a cup in the shade.

3. More whining, but move forward with the contest.

4. What isn’t fair?  (Too many variables, both should either be in the shade or under the lamp.)  Talk about what would make the contest more fair.  Try putting both candies under the lamp.

5. Follow your new procedures for the contest, controlling for outside variables.

6. Discuss how it went.  What was the independent variable in this contest?  (the type of the candy)  What was controlled?  (the size of the candy, the amount of heat, the plastic cup)

The Bounce

Materials: beach ball, kickball, measuring tape

1. Stay in your teams, Team 1 and Team 2.

Beach Ball vs. Kickball

2. This is the final contest.  You’re going to see which ball will bounce the highest.  Team 1 can drop the beach ball from 5 feet in the air.  Team 2 can drop the kickball from 2 feet in the air.

3. Hold the contest.

4. What was unfair about the contest?  (The balls were dropped from different heights.)  Talk about what would make the test more fair?  Should the ball be dropped from the same height?

5. Follow your procedures for the new contest.

6. Discuss how it went.  What was the independent variable? (type of ball)  What was controlled? (the height the ball was dropped from, the surface it was dropped on)

Follow Up

When we’re doing experiments, we have to make sure our tests are fair.  Otherwise, our results might not be accurate.  Example:

Do marigold seeds that receive sunlight grow taller than marigold seeds that receive no sunlight?  In this situation, it’s sunlight vs. no sunlight.

Let’s say I forgot to bring enough water outside to water all the seeds equally.  Instead I just watered the seeds receiving no sunlight.  Is that fair?  No; the test is sunlight vs. no sunlight.  Water is not part of the test, so I must always water the seeds with same amount of water each time.

 Science Process Skills Resources

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