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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:.
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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.