Control & Variable Notes

Where do I start?

• After you have a question that you want to answer using the scientific method, there are a few important things you need to think about while setting up your experiment.

Example Question #1:

• Does heating a cup of water allow it to dissolve sugar faster?

THE CONTROL

• A control is the part of the experiment that remains the same.

• It may also be called the constant.

How to Remember:

• WHAT I KEEP THE SAME

Back to the Example

• Question #1: Does heating a cup of water allow it to dissolve sugar faster?

• Control #1: Type of water, Type of sugar, amount of water…

CONTROL GROUP

• The control group provides a baseline for comparison.

HOW TO REMEMBER:

• LEAVE OUT WHAT YOU ARE TESTING

Back to the Example:

• Question #1: Does heating a cup of water allow it to dissolve sugar faster?

• Control #1: Type of water, Type of sugar, amount of water…

• Control Group #1: Room temperature water

What is a Variable?

• A variable is the part of the experiment that changes. An experiment usually has two kinds of variables: independent and dependent.

INDEPENDENT VARIABLE

• The variable that is changed by the scientist.

• To insure a fair test, a good experiment has only ONE independent variable. As the scientist changes the independent variable, he or she observes what happens.

HOW TO REMEMBER:

• WHAT I CHANGE

Back to the Example

• Question #1: Does heating a cup of water allow it to dissolve sugar faster?

• Control #1: Type of water, Type of sugar, amount of water…

• Control Group #1: Room temperature water

• I.V. #1 : Temperature of the water

DEPENDENT VARIABLE

• The variable that is caused by the change the scientist made.

• The scientist focuses his or her observations on the dependent variable to see how it responds to the change made to the independent variable.

HOW TO REMEMBER:

• WHAT I OBSERVE

Back to the Example

• Question #1: Does heating a cup of water allow it to dissolve sugar faster?

• Control #1: Type of water, Type of sugar, amount of water…

• Control Group #1: Room temperature water

• I.V. #1 : Temperature of the water• D.V. #1: How fast sugar dissolves

Example #2:

• Question #2: Does fertilizer make a plant grow bigger?

Example #2:

• Control(s): size of plant size of pot amount of soil type of soil amount of water

Example #2:

• Control Group:

A plant with no fertilizer

Example #2:

• Independent Variable (What I Change):

Amount of fertilizer

Example #2:

• Dependent Variable (What I Observe):

Height of plant

Example #3:

• Question #3: What type of dish soap best removes spaghetti sauce stains from plates?

Example #3:

• Control(s):

amount of sauce

type of plate

amount of dish soap

Example #3:

• Control Group:

Using just water to wash

Example #3:

• Independent Variable (What I Change):

type of dish soap

Example #3:

• Dependent Variable (What I Observe):

Amount of sauce stain leftover.