Control Variables A control variable in an experiment

Control Variables

• A control variable in an experiment is something that stays the same through out the experiment while the other variables change. • Changing Variables- what changes in the experiment.

For example: In Mobey and Tim’s experiment. They used the same type of fig plant while only changing the amount of water they gave each plant. What was the control and what was the changing variable being tested?

The control variable: The type of plant (stayed the same). Variable that changed: The amount of water they added to each plant.

Identify the control variable Tim wants to know if sugar dissolves better in warm water. He puts the same amount of sugar in three different glasses. One has cold water, one has room temperature water, and one has hot water. Cold Water Room Temperature Hot Water

• The amount of sugar added to each glass was the same and therefore the amount of sugar is a control variable. • The temperature of water in each glass was different and therefore the temperature of water was a changing variable or manipulated variable.

• If you do not have a controlled experiment (one that contains control variables), then your results will be inaccurate!

Why couldn’t Mobey and Tim have set up their experiment like this to test if watering a plant too much would cause it to die? A Flower Plant A Never watered A Cactus Plant B Watered everyday A Tree Plant C Watered 3 times/week A weed Plant D Watered once/week

Designing an Experiment using the Steps of the Scientific Method 1. State the Problem 5. Analyze Results 2. Form a Hypothesis 6. Draw a Conclusion 3. Set Up a Controlled Experiment 7. Publish Results 4. Record Results 8. THEN REPEAT!!! (if repeated experiments give the same results then your conclusion becomes a _______!