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Science Fair Projects on Measuring Variables

Experiments are methodical procedures that aim to establish cause and effect relationships between two factors, and thereby help validate a theory by observing how changes in one factor alter the other factor. These changing quantities are knows as variables. A good science fair project on measuring variables consists of variables that can be measured and quantified accurately using calibrated devices. The project should also have an independent variable that can be altered by the researcher or the student, and can cause changes in the other variable, known as the dependent variable. All the other factors, or controlled variables, involved in the procedure should remain constant.

Sugar and Water
- A simple experiment that involves heating a cup of water to determine if it will dissolve more sugar can help demonstrate the concept of measuring variables. The temperature of the water is the independent variable, and is measured in degrees Celsius or Fahrenheit. The dependent variable is the amount of sugar that can be dissolved in the hot water and measured in grams. The amount of water, the type of sugar and stirring are the controlled variables and should remain stable throughout the experiment.
Electric Motor and Voltage
- Set up this experiment by attaching an electric motor to a wheel. Vary the voltage of the motor and observe the changes in the motor's output. The voltage is measured in volts and is the independent variable. The output is indicated by the movement of the wheel, and measured in revolutions per minute. The controlled variables, including the motor and the wheel, remain same through the experiment.
Balloon and Vinyl Tubes
- Insert pieces of vinyl tubing, available at most hardware stores, into the mouth of the balloon and then, blow it. Measure the diameter of the balloon before releasing it, and measure the distance travelled by the vinyl tubing as it flies out of the balloon. The diameter of the balloon is the independent variable while the distance travelled is the dependent one. Both can be measured in centimeters or meters. The type of balloon and the pumping device should remain constant as they are the controlled variables.
Household Cleaners and Bacteria
- Inoculate a sterile petri-dish containing nutrient agar with a strain of common bacteria such as Escherichia coli or Staphylococcus species. Use a sterile cotton swab to distribute the bacteria uniformly across the petri-dish. Take two small squares of blotting paper with exactly same dimensions. Soak one of them in the cleaning agent of your choice and the other one in sterile water. Place both the squares on the petri-dish and incubate overnight at 37 degrees Celsius in an incubator. If the bacteria are killed by the cleaning agent, they will not grow around the square with cleaning agent but grow everywhere else. Measuring the area of clearing around the sensitivity square in millimeters indicates the effectiveness of the cleaning agent. Repeat the experiment using other agents. The concentration and type of clearing agents used are the independent variables while the area of clearing is the dependent variable. Controlled variables such as type of bacteria, time and temperature of incubation, and type of agar should remain constant.

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