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Investigation Question 3:
How does water move through soil?
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What To Do
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Setting the
Scene
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Tell the students that they will test four materials for how much water they hold and how much water they allow to drain away in a set amount of time.
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© Michael Collier |
Excess water drains from this field near Hollister, California. |
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Presenting the Investigation
Question
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After the scene is set, introduce your students to the investigation question: “How does water move through soil?”
Tell your students that they will be investigating this question and that at the end of their investigations, they will be able to provide reliable answers.
Have your students brainstorm ideas about how this investigation question could be investigated.
- Design an experiment that could be used to test the investigation question.
- What materials would be needed?
- What would you have to do?
- What would be measured?
- How long would the experiment take?
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Assessing What Your Students Already Know
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If you have a potted plant growing in the classroom, show it to the class. Pick up the pot, and have the students notice that there is a hole in the bottom of the pot. Ask why the hole is there, and why they think you put a saucer under the plant. (Students will probably know that the hole allows water to drain.) Ask the students what would happen if you watered the plant and there was no drainage hole in the pot. (They will say that the soil gets “soggy”, “too wet”, “full of water”. They may even say that this would not be good for the plant.)
Ask a student to water the plant as you hold it above the saucer. Let everyone observe water dripping from the drainage hole. Ask “Did as much water drip out of the plant as we put in the top?” Students will begin to think about soil’s ability to hold water as they watch this occur.
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Exploring the Concept
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- Show students that the 5 smaller containers, just like the flower pot in the classroom, have holes in the bottom through which water can drip. Demonstrate how the large cup can be inserted into the smaller cup so that water can be collected below. You might want to pour water in an empty setup so that they see how water passes through the hole to collect in the smaller cup below.
- If your students are experienced investigators, you can challenge each group to design a fair test of the four materials (soil, sand, gravel and clay) using the materials you provide. You will need to approve the procedure before they begin their tests. As you review each plan, check that they have controlled the variables—volume of material, volume of water, time interval (if they ask, suggest they start with 15 seconds for all of the samples and adjust the time if that seems to be too long or too short for seeing results in the majority of the samples.)
- Be sure that the students have set up a table for recording the results of the experiment. There are several ways that the students can collect their data. They can simply mark the cup with a line showing the amount of water drained in the given time period. (They can measure the height of this line using length units.) Or, they can actually measure the drained amount using the measuring cup or cylinder.
- Have the students perform their experiment, record their data, and, finally, display their data on a bar graph (histogram). Give them time to share their fair tests and their results.
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