¨ Must have ONE manipulated variable (the variable that is changed in the experiment)

¨ Must have a high degree of control, either in the form of a control group or controlled conditions

¨ Must be able to use the scientific method

Sample Questions

How is magnet strength affected by temperature?
What effect do preservatives have on the growth of bread mold?
What fabrics make good insulators?
What materials are the best conductors of electricity?
What effect does the height of a swinging mass have on its energy?
What effect does temperature change in water have on a fish’s rate of breathing?
How does heating water affect the rate at which materials dissolve?
What effect does size of particles have on how fast a solute dissolves?
What is the effect of different kinds of physical activity on pulse rates?
What is the effect of different types of practice on learning rates?

Examples with the scientific method

Example 1:
Question:  How does temperature affect the life of a battery?
Hypothesis: Batteries stored in cool temperature will last longer; the colder the storage, the longer the life. The differences remain to be measured.
Manipulated variable: Temperature
Responding variable: Life of battery
Controls: Kind, size and age of battery
Measurement of responding variable: Length of time the battery will operate the same item.

Example 2:

Question: What effect does the shape of a hole in a parachute have on its falling speed?
Hypothesis: Shapes that interfere with the passage of air should cause a slower fall if the chute remains stable. The differences remain to be measured.
Manipulated variable: Shape of hole
Responding variable: Speed at which parachute falls
Controls: Area of hole, size and shape of parachute, length of fall
Measurement of responding variable: Length of time for parachute to fall

The scientific method is the “tool” that scientists use to find the answers to questions. It is the process of thinking through the possible solutions to a problem and testing each possibility to find the best solution. The scientific method involves the steps outlined below:

1. Select a question

• Use books from the library or the Internet for ideas and information
• Be sure your question can be answered by conducting an experiment
• Open-ended questions work best. For example: “How does light affect the growth of mold?” instead of “Does light affect mold growth? “ Try to avoid yes or no questions.
• Be careful! Many resources suggest science fair experiments that are not true experiments. In a true experiment, you will be able to identify the manipulated, responding, and controlled variables (see below).

2. Research

• Process of collecting information from personal experiences, knowledgeable sources, printed sources (books, journals, magazines, newspapers), as well as electronic sources (computer software and Internet sites).
• Research or background information should help in determining the hypothesis (see below).

3. Form a hypothesis

• Prediction about what you think will happen as a result of your experiment
• Often referred to as an “educated guess”
• Should guide you in designing the procedure for the experiment that will prove or disprove the hypothesis

4. Perform the experiment

A. Plan the experiment

• Identify the manipulated, responding, and controlled variables

• Manipulated Variable: This variable (sometimes called the independent variable) is the one you will change in your experiment. For example, if you wanted to know how temperature affects the life of batteries, the temperature of the batteries being tested is the only variable that you would change.
• Responding Variable: This variable (sometimes called the dependent or outcome variable) is the thing that changes as a result of the changes in the manipulated variable. If you were testing the batteries in a flashlight, the responding variable would be the length of time the flashlight would work with batteries that had been kept at different temperatures.
• Controlled Variables: Sometimes called controls, these are all the things that you keep the same in your experiment. Controls in the battery example would be the brand, size of battery, the shelf-life date, kind of flashlight, and length of time each battery had been held at each temperature, and anything else that might affect the results.

B. Select the materials to form the test equipment. Plan how the tests will be done. Keep the

following questions in mind:

• What tests will you do first?
• How many tests will you do?
• How will the data (results) be recorded?
• How many times will each test be repeated?

C. Assemble equipment and prepare data sheets for recording measurements and comments.

D. Conduct the experiment

• Be sure to make careful observations and record all information gathered.
• Repeat each test several times to be sure results are valid.

5. Prepare the results

• Organize the data you collected. Make charts, graphs and/or tables to show what happened.
• Whenever possible, use numbers to show your results.
• If something happened that you could not explain, you may choose to do more tests or make different measurements to help answer your question.
• If one measurement is very different from the others, check your comments from your observations to be sure nothing unusual happened to that test. For example: If you were testing the effect of temperature change on batteries and you dropped the flashlight, your results from that test might not be accurate. Try to understand the problem so that you can explain unusual results.

6. Explain the results

• Study your results and begin thinking about what your charts, graphs, and tables tell you.
• Pay close attention to patterns in your data.
• Try to explain how or why the results came out the way they did. What was the cause?
• Do your results agree with your hypothesis?
• You are encouraged to do additional research to help explain your results.

7. Draw conclusions

• What can you say about your experiment in general?
• What do you think would happen if someone did a similar experiment?
• Comment on any patterns and amounts in your conclusion.
• If possible, describe how your results might apply to everyday experiences.

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