sciencepalooza! 2017 – Experimenting
A science procedure needs to be as specific as a cooking recipe. Any high school student should be able to pick up your procedure, follow it, and get very similar results.
- Use numbered steps.
- Write your procedure in paragraph form.
- Include your safety precautions. For example, using acids requires gloves and goggles.
- Think about controlled variables. One of the most common mistakes students make is proposing the testing of a group of plants inside and trying to compare the results to a group of plants outside. The 2 groups of plants will experience differences in light, temperature, humidity, wind, and insect exposure. Even when all the plants are inside, they must be in the same part of the room to be compared fairly.
- Include concentrations, molarity, and amounts of chemicals.
- Specify the units—the labels we use to tell us what a number means. When a recipe tells you to use “5” of sugar, it specifies what the 5 refers to—teaspoons, tablespoons, cups, etc. It makes a difference!
- Use metric units—grams, liters, Newtons, and degrees Celsius, rather than pounds, inches, and degrees Fahrenheit.
- Begin your procedure with “Gather materials.”
Here is an example of a well-written procedure, based on studying triclosan, the active ingredient in antibacterial soap:
- Prepare a brine shrimp hatchery according to the directions on “wikihow.com.”
- Add 800 eggs to the hatchery.
- After 4 weeks divide the shrimp into 4 groups.
- Make salt-water solution using 35 grams of sea salt to every liter of water.
- Fill each of 4 tanks with 4 liters of salt water, adding a bubble aerator to each tank.
- Place 200 brine shrimp in the “control” tank.
- Place 200 brine shrimp in each of 3 other tanks.
- Add 1 gram of triclosan to a liter of salt water. Label “Stock A”.
- Pour 10 ml of the Stock A triclosan solution into the first tank. Label the tank “250 ppb”.
- Pour 10 ml of the Stock A triclosan solution into 90 ml of salt water. Label “Stock B”.
- Pour 10 ml of the Stock B solution into the second tank. Label the tank “25 ppb”.
- Pour 10 ml of the Stock B solution into 90 ml of salt water. Label “Stock C”.
- Pour 10 ml of Stock C into the third tank. Label the tank “2.5 ppb”.
- Add 10 mg of yeast to each of the 4 tanks.
- Position the tanks so that each has a day-and-night cycle of light. Do not place any tank in direct sunlight. After the first 7 days scoop 250 ml out of the control tank and count the brine shrimp in the sample.
- Repeat with 2 more 250-ml samples of water and record and average findings. Return samples to tank.
- Repeat steps 14 and 15 with Tanks A, B, and C.
- Add 10 ml of Stocks A, B, and C to the appropriate tanks.
- Add 10 mg of yeast to each tank.
- Replace any evaporated water.
- Repeat steps 15-20 after 14, 21, and 28 days.