The Difference Between a Science Demonstration and a Science Experiment

For our mummification experiment, the apples are waiting for the different substances we will add.

For this week, I thought I would show you the experiment we are currently working on, and to talk a little about one of my biggest pet peeves...the difference between a science demonstration and a science experiment.

Student wrapping his mummified orange/potato in gauze.

While studying Ancient Egypt a few years ago, we mummified oranges and potatoes. Although my youngest participated in that, he wants to do it again since he was so young when we did it before, so we will be mummifying oranges and potatoes using table salt and baking soda for the natron the Ancient Egyptians used.

But this year, I thought I would add an science experiment in addition to the the mummification project.

I have seen this done many times on various blogs. We took six plastic disposable cups and put an apple slice in each one. 

In one we added 1/4 cup Epsom Salt.

In one we added 1/4 cup Baking Soda.

In another, 1/4 cup table salt.

In two cups we added a combination of two substances; one we added a mixture of a 1/8 cup Epsom salt and 1/8 cup Baking Soda...

and in the other a combination of Table Salt and Baking Soda.

In the last cup, we left the apple alone, and labeled it "Control."

A control is part of a scientific experiment. It is a portion of the experiment that is separated from the rest of the experiment. This isolates the independent variable's effects on the experiment and can help rule out alternate explanations of the experimental results.

source: Science Fair Coach

I call a science activity that complies with the scientific method, "an experiment." If the activity does not comply with the scientific method, then I call it "a science demonstration." I have seen lots of science books that do not use this rule, and call demonstrations, "experiments."

Although technically an experiment can include personal and informal demonstrations, such as a cola taste test in

order to determine what tastes the kids like best, I think it is important to begin early establishing the difference between the orderly proving of a scientific conclusion and an observation. Both are important to do, but they are quite different and talking about the difference from the beginning is a simple and important way to teach the scientific method.

An easy way to tell the difference is to ask yourself, does what we are doing prove a scientific principle or does it just show one?

For example, the process of Extracting DNA from Strawberries is a great, fun demonstration, but it does not prove that what you see is DNA. You have to take our word for it.

This experiment, on the other hand, complies with the scientific method, and is, therefore an experiment.

Step 1: Ask a Question: What substance dries up an apple slice quicker and more thoroughly? This is not the greatest question because qualitative in nature. A better question would include some method of measuring the moisture left inside the apple slices.

Step 2: Make Observations and Conduct Background Research: We have learned that the Ancient Egyptians used Natron to dry out their mummies. We have also learned that Natron was mostly sodium carbonate. What do we have on hand that we can use to dry out an apple slice and simulate Natron?

Step 3: Propose a Hypothesis: We got together Epsom Salt, Table Salt and Baking Soda and we made our educated guesses about which would work the best.

Step 4: Design an Experiment to Test the Hypothesis: We tried to make the slices the same size and we tried to make everything except the substances added to the cups exactly the same. It would have been better if we weighed the slices and made them exactly the same, but I let that go.

Step 5: Test the Hypothesis: Since some of us hypothesized that a combination of substances would do the best, as Natron really is a combination of ingredients, we had to include combinations of the substances as well. We made sure that we have the same amount of the ingredients; the all equaled 1/4 cup.

Step 6: Accept or Reject the Hypothesis: We haven't arrived to this step yet, but we are prepared for it!

Step 7: Revise a Rejected Hypothesis (return to step 3) or Draw Conclusions (Accepted): We are all anxiously waiting to come to this step.

This all is not to say that demonstrations are not as good. In fact, most of the science explorations we do, especially in the pre-high school grades are demonstrations. I just think it is important to know the difference.