Fun with the scientific method

Mrs. Kepler, the aquarium is all green again. Every Monday morning this past spring, my third-grade students made this observation. Without the daily scrubbing by the children, the sides of the tank grew a thick covering of algae. But why was this happening, they wanted to know.

Without realizing it, my students had already taken the first two steps on a path of learning known as the scientific method. They had made an observation and asked a question. All I had to do was guide their inquiry along the remaining steps in the path.

Beyond the Question

Preferring to see the fish in the tank and not the algae, my students and I agreed we needed to figure out why it was turning green and what to do about it. We guessed that the tank might be turning green because there was too much sunlight, too many fish, or too high a water temperature.

We weren't ready to give up any fish, so we decided to follow up on the "too much sunlight" idea. After all, the aquarium did sit right on the windowsill and did receive a lot of sunlight. But this was still just a guess, so we needed to develop a hypothesis, a theoretical statement that can be tested.

On the board I wrote the beginning of the hypothesis, "The algae is growing thick in the aquarium because..." and let my students decide how to finish the statement. We ended up with, "The algae is growing so thick in the aquarium because it is in direct sunlight."

The Experiment

With our hypothesis in hand, our next step was to think up an experiment that would allow us to determine if our hypothesis was correct. We decided that we needed to move the aquarium from the windowsill to a location that didn't receive direct sunlight, and to not scrub the walls as usual.

When we had moved the tank to the other side of the room, we were ready to begin observing the results of our investigation, the next step in the scientific method. The children watched for signs of green on the tank walls and recorded their observations daily in the class journal we were already keeping on our fish observations.

By Friday afternoon, our tank was still crystal clear, but we agreed the real test would be to see how it looked after the weekend.

The Conclusion, Please

The next Monday morning, my students' usual quandary over the algae was replaced with squeals of delight as they looked at the aquarium and viewed the final results of our experiment. "Mrs. Kepler, we did it! The green is gone!"

It was now time for the sixth and final step in the scientific method, to make a conclusion of exactly what we thought was happening in the tank. Through a group discussion, we concluded that the greater amount of sunlight in our aquarium's previous location was the most likely reason we had so much algae growth on the glass walls. Less sunlight meant less algae growth.

I pointed out to the children that even though we had guessed this (our hypothesis) before we moved the tank, it was only after we had moved it (our experiment) and saw what happened (our results) that we could be pretty sure what was going on (our conclusion).

I also explained that if our results had indicated that our hypothesis was wrong, we would have figured out a new hypothesis and tested that one.

Reviewing the Process

To help reinforce the children's understanding of the scientific method, we charted our process on the chalk board. First I drew six large columns and asked the children to help me label them with the steps of the scientific method.

In the top half of each column, we listed all the things we had done for that step. In the bottom half, we listed why we had done those things. For example, on the top of the "Experiment" column we wrote, "Moved the fish tank away from the window." On the bottom we wrote, "To see if the sunlight was making the algae grow."

Finally, I divided the class into small groups. There was one group for each step of the scientific method we had followed. On large pieces of white paper, each group illustrated and labeled the step. We placed these out in the hall, so that we could share our discovery with the other students who walked down the hall.

The Scientific Method Is Fun!

Filled with wonder, children are constantly asking questions about the world around them. The scientific method offers them a concrete way to explore their questions. By introducing your students to this way of thinking and showing them that it's a fun and versatile tool, you will provide them with a powerful way to engage in a lifetime of learning.

Lynne Kepler is a third-grade teacher at Clarion Limestone Elementary School in Strattanville, Pennsylvania. She has written a number of books on teaching science, including A Year of Hands-on Science (Scholastic Professional Books, 1996).

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