TAC Experiment - Lesson Plan

Lesson Plan
Brainstorming, researching and proposing an experiment

  1. Have your students take out a sheet of paper and fold it in half vertically.
  2. Title one half “Things that might help the mini-ecosystem in my terraqua column”. Title the other half “Things that might hurt the mini-ecosystem in my terraqua column”. Divide the board into two columns as well.
  3. Give students 3-5 minutes to come up with ideas for each side of their paper. For now, allow students to interpret “help” and “hurt” in any way they want. If students are having difficulty thinking of ideas, ask questions like:
    • What do people do that is good for the environment in general?
    • What do people do that is bad for the environment in general?
  4. When 5 minutes have passed, ask students to share their ideas with you. Write their ideas up on the board as they are suggested. One effective way to do this is to go around the room and have each student share one idea before opening it up to anyone to share a second or third idea. It is likely that different students interpreted the question differently – some might think about re-engineering the terraqua column while others might think about ways to help the plants grow better. This is GREAT! You can draw attention to these different interpretations as they appear.
  5. Tell students that they will now have a chance to change one thing about their terraqua column and compare the changed column to one without the change. Using the ideas on the board, go through a couple examples of things that they might want to change.
  6. Emphasize the importance of having two columns, one to make a change in and one without the change to compare the other one to. For instance, consider an imaginary student Bill who wants to know how adding fertilizer might affect the plants. He builds a terraqua column and adds fertilizer. The plants grow to be 20 centimeters tall. Can Bill conclude that the fertilizer made the plants grow taller? No! Taller than what? Without a column that was the same in every way except that it didn’t get fertilizer, Bill doesn’t have anything to compare the 20 centimeter plants against. If you want to introduce the associated vocabulary (experimental group, control group) then do so here.
  7. Emphasize the importance of changing only one thing. Lead students through several example experiments where several variables were altered simultaneously. For instance, think about Bill and his fertilizer experiment. Bill also thinks that garden soil is probably better for plants than school yard soil. So, in one column he plants seeds in garden soil and uses fertilizer. In the other column he plants seeds in school year soil and no fertilizer. In the end, the plants in garden soil and fertilizer grew taller. Can Bill conclude that the fertilizer made the plants grow taller? No! Maybe the garden soil made them grow taller. You can’t tell which variable caused the plants to grow taller if you change more than one variable at a time! If you want to introduce the associated vocabulary (independent variable, dependent variable, and controlled variable) then do so here.
  8. Divide the kids into their teams. Tell them to design an experiment with their terraqua columns. In their lab notebooks, have them write out their idea in words and also draw a picture of the two columns illustrating what they plan to do. Circulate around the room to help groups who are having trouble settling on a single thing to change.
  9. Once most groups have an idea of what they want to do, ask students to predict the differences between the plants, water and soil in the two columns. These predictions should be as specific as possible. “The plants will grow better” is not enough. Aim for details such as “the plants in the column with fertilizer will sprout earlier, will be taller, and will have more leaves than the plants without fertilizer.” The end goal is for students to choose 3-4 things they can measure over the next month. Again, circulate around the room to help groups make predictions and choose 3-4 dependent variables to measure.
  10. Before students turn in their experiment designs, make sure they all have the following 4 things written down:
    • The idea behind the experiment in words
    • A labeled picture of the two columns they plan to build
    • Predictions of the differences between the plants, water and soil in the two columns
    • A list of 3-4 measurements they plan to make 2-3 times a week for the next month
  11. When they are finished, have them turn in the experiment design to you for approval before they can actually do it. Depending on your students, you may need to go through several rounds of revisions before they have an acceptable experiment designed.

Setting up the experiments

  1. Make sure that all teams have a well designed experiment and have all the materials they need.
  2. Give students at least 20 minutes to build their columns and make their initial observations.

Making observations and recording results

  1. 2-3 times a week for the next month, students need an opportunity to make observations of their columns. Each time, they should make the same set of 3-4 measurements in both columns. You may wish to conduct periodic checks of their lab notebooks to ensure that the date of each observation and all the data is being recorded.

Organizing and presenting the results

  1. At this point, students should have 8-12 observations for each of the dependent variables the students chose. There should be a lot of data. The first task is for each group to go through their lab notebooks to organize the data and look for patterns. The best way is generally to create a table like the one below for each type of measurement that was made:
    pH of the water     
     Date Column with fertilizer Column without fertilizer  

    I showed students 2 examples of how to create tables of their data (picking the types of measurements most common within the class – height of any plants and water pH) then let them get started.

  2. Next, students should look for patterns in each table. Often, graphing the data (if it is numerical) helps. The younger students may have difficulty graphing and may need more instruction about how to set up the axes of the graph and how to plot the data.
  3. Finally, have students summarize any other observations that weren’t on the original list of planned dependent variables. For example, “On 11/18/04 the column with fertilizer tipped over and all the soil and water spilled out.” Or “On 11/30/04 fuzzy white mold appeared on the surface of the soil in the column without fertilizer.”
  4. Have students draw conclusions. The questions I asked my students were:
    • Go back and read the idea behind your experiment. Then look at the patterns you observed. What did you discover? Use your measurements and observations to describe how the terraqua columns were affected by the change you made.
    • Go back to your predictions. Use your measurements and observations to explain why your hypothesis was right, wrong, or why you cannot tell.
    • What you would do differently if you were to do this experiment again?

    Naturally, you can create different questions or reword them to suit your own classroom.

  5. Finally, have students share their experiments with the class. This may be done orally or through a “poster session”. If you wish to have your students create posters, it is helpful to create one of your own with fake data so that they have an idea of what is expected. Once the posters are made, they can present their posters to the class.