SKILL BUILDER - Separating and Controlling Variables

Scientist pay close attention to controls, dependent variables, and independent variables when they design experiments. Do the Chaper 3 Skill Activity on page 844 to learn how to identify controls and variables. How to identify control and variables.

Procedure

1. Pour the same amount of water into two beakers.

2. Take the temperature of the water in each beaker to make sure the temperature are the same.

3. Add salt to one beaker and stir the water in both beakers until all the salt has dissolved.

4. Take the temperature of the water and of the salt solution.

5. How did dissolving salt in one beaker affect th water temperature?

6. What were the controls? Variables?

The scientist take great care to make sure only one factor in the experiment, the independent variable. The independent variable is the "cause" factor.

The factor that changes as a result of the independent variable is called the dependent variable. The dependent variable is what is measured or observed. It is the "effect".

The controls are factors that are kept the same, providing a basis for comparison . In order for the test to be fair, other factors that could affect the outcome of the experiment should be kept the same, or controlled.

The salt is the independent variable.

The temperature of water is the dependent variable.

The volumen of water is the control in the experiment.

Practicing the Skill

1. Ten grams of sugar dissolves more quickly in a liter of pure, hot, tap water than it does in a liter of pure, cold, tap water. List the controls, the indepent variable and the dependent variable.

The control is the volume of water.

The temperature and the sugar is the independent variable. 

The velocity of dissolves the sugar in the water is the dependent variable .

2. Identify the dependent variable from testing the following hypothesis: If premium gasoline is more efficient, then it should increase the fuel mileage of our family car.

The control is the volumen of gasoline.

The type of gasoline is the independent variable.

The distance traveled is the dependent variable.