Objective:
The student will be able to compare and contrast differences in water quality by observing and recording changes to water during an experiment in control and polluted environments.
Materials Needed:
*These materials should be brought in kid-safe containers. The teacher should handle and dispose of all materials when the experiment has concluded.
Activity:
Before beginning this experiment, engage students in a discussion of the importance of water quality for humans. Using the chalkboard, make a list of the many ways we use water and then make a list of the pollutants that would poison our water supply.
Then, ask the students to consider why water quality is so important to fish—not only those in the classroom aquarium, but also for fish in lakes, ponds, rivers and oceans. Ask students to make predictions about what happens to water that is polluted by chemicals or that is stagnant.
Divide the class into several small groups. Have labels ready to put on cups as they are filled with different ingredients.
First, prepare a “control” cup by placing the crushed charcoal as a filter on the bottom, pressing the roots of an aquatic plant into the charcoal, filling the cup with clean tap water and positioning this cup away from immediate sunlight. At least once a day, a student should insert a straw about 1/8 inch into the water and blow a few gentle puffs of air into the water. (Teachers should supervise to ensure that students blow out, not suck in.) This will simulate the filtration and exchange of gases that must take place within a healthy aquarium.
For the remaining cups, first place the aquatic plant on the bottom (with no charcoal), fill with clean tap water and…
1. Put two teaspoons of motor oil in one cup.
2. Put a teaspoon of dishwashing detergent in one cup.
3. Put a teaspoon of clothes detergent in one cup.
4. Put some non-water-soluble paint in one cup.
5. Put two teaspoons of sugar in one cup.
All cups (except for the control cup) can be placed in a windowsill, which will enable students to easily measure the effect of evaporation in addition to the impact that the “pollutant” has on the water quality inside the cup.
Ask students to make predictions about what will happen to the water quality in their cup.
Result:
Each day, students can observe the change in water quality of the cups in the windowsill compared to the control cup. Different groups of students can be responsible for observing and recording data on different cups. At the end of a specific time period, groups can report their findings to the class. Ask students to comment on what their findings mean to the fish and plants that must have clean water to survive in their underwater habitat.
