Skill Builder

Homework Science

Separating and Controlling Variables 

Scientists pay close attention to controls, dependent variables, and indedependent variablesn when tey desingn experiments. 
How to identify controls and variables?


See if you can identify the controls and variables in the following Skill Activity:


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 untill all the salt has disolved.
4. Take the temperature of the water and of the salt solution.
5. How did dissolving salt in one beaker affect the water temperature?
6. What were the controls? Variables?

The indepent variable, also know as manipulated variable, is at the center of any quantitative experimental desing.

In any real experiment, an investigator manipulates an indepent variables to influence one or several dependent variables

The controls are factor that are kept the same, provinding a basis for comparison.

In the previous experiment the controls and the dependent and dependent variables are the following:

Independent variables:

- The amount of water

- The amount of salt in the water.

Dependent Variables:

- The rate of dissolution of the salt depends on the temperature of the water

The controls of the experiment are:

- The shape and size of beakers

- The amount of water


In Practicing the Skill
1) The Controls
- Ten grams of sugar
- The amount of water
-

The Independent Variables
-  The temperatura of water
-  The quality of water

The dependent variables.
- The rate of dissolution of sugar

2) The dependent variable is the increase the fuel mileage of our family car