MAKE A Plan! – planning an experiment

MAKE A Plan! – planning an experiment – Brief Article

Nicole Dyer

Here’s a science project to drool over. But first you need to …

A gob of spit may be the perfect gross-out, but saliva’s real job is to soften and partially digest the food you eat. Spit contains a special enzyme (protein) designed to break down large sugar molecules–called starches–into small (simple) sugar molecules. Bread contains mostly starches, for example, so it turns to mush when it remains unchewed in your mouth. But just how fast does saliva work to dissolve starchy foods, like bread and bananas? How about foods made of simple sugars like chocolate? Or sugarless foods? Try out this mouth-watering science project!

Your first task is to brainstorm and formulate a research question. For instance: How long does it take saliva to dissolve four different foods? The best way to find the answer is to make a step-by-step procedure, or plan. At first, your procedure might look like this:

Initial Procedure

1. Place 1 piece of bread in your mouth.

2. Record the time it takes for the bread to dissolve.

3. Repeat steps 1 and 2 with a piece of banana, chocolate, and spinach.

Seems simple, right? But if this is truly a science project to drool over, your friends should be able to repeat the experiment exactly as you did. But they can’t without better instructions. The initial procedure lacks important details, like what size should the pieces of food be? Should you chew the food, or just let it sit on your tongue?

With a well-detailed procedure, anyone can repeat the experiment exactly the way you did it. Rewrite your procedure using these tips:

* What materials will you need? Make a list, including amounts and measurements.

* Test one independent variable (the change you are testing) at a time. In this experiment, your independent variable is the amount of time it takes to dissolve different foods in your mouth.

* For reliable results, keep all other variables, like the size of the food pieces, constant (unchanged).

* Be sure to include a control, or standard, with which to compare your results. That’s where spinach comes in; it serves as your control because the leafy veggie is starch-free.

* To verify your results, repeat the experiment. Possible glitches in the first trial can skew your results.

Armed with that advice, spit-shine your initial plan. Your newly polished procedure should be clearer and easier to duplicate.

Finally, check your procedure for accuracy, completeness, and safety. Are your instructions clear? Can they be easily followed? Have you left out any steps? It helps to have someone else like a friend or family member review the experiment to see if she or he can follow the steps. Depending on the feedback you get, you may have to revise steps or add new ones.

For example, instead of using a 2 cm (0.8 in.) cube of bread, you may want to use a 1 cm (0.4 in.) cube. Or you may want to try chewing food pieces twice to see what effect this has on the dissolving time. When you think your plan is drool-worthy, conduct a trial run. Are there ways to improve your experiment?

Polished Procedure


* 1 slice of white bread * 1 banana * spinach * 1 plain chocolate bar * paper cup * ruler * knife * paper * pencil * stopwatch

1. Using a ruler and knife, chop the bread and banana into 2 cm (0.8 in.) cubes. Cut the chocolate and spinach into pieces that are 2 cm (0.8 in.) long.

2. Place the cube of bread in your mouth. Close your mouth. Do not chew or move the bread around.

3. Record the amount of time it takes for the piece of bread to dissolve (until it becomes liquid). Spit the bread “juice” into a paper cup.

4. Repeat steps 2 and 3, this time chewing the bread twice before you let it sit in your mouth.

5. Repeat steps 2 to 4, using the piece of banana.

6. Repeat steps 2 to 4, using the piece of chocolate.

7. Repeat steps 2 to 4, using the spinach (spit the spinach into a cup after one minute).

8. Repeat the experiment 3 to 6 times. Calculate and record the average time it takes to dissolve each type of food. Compare your results with your classmates’ results.

Make a Plan!

Directions: After reading “Make A Plan”, fill in the blanks.

1. The best way to find an answer to a research question is to make a step-by-step –.

2. In an experiment, the variable being changed is called the — variable.

3. Your experiment should include a –, or standard, with which to compare your results.

4. Variables that remain unchanged are held –.

5. Spit contains a special — designed to break down large sugar molecules.


1. procedure 2. independent 3. control 4. constant 5. enzyme

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