Is the Water Safe?
- Grade Level:
- Upper Elementary: Third Grade through Fifth Grade
- State Standards:
- ESS2.C, ESS3.C, PS1.B
- 2 gallons distilled water
- 1 empty and washed gallon milk jug
- Salt or sugar
- Dry Erase Marker
- Cups so that each student has 2, these can be 4oz. bathroom dixie cups
Key Vocabulary: odor and flavor threshold
Background: Flavorless water is not always safe. Most pollutants are tasteless at dangerous levels. The level at which we begin to detect a flavor or odor is the odor and flavor threshold.
1. Before class, add salt or sugar to one of the gallons of distilled water and make sure that you can taste it, but that it is all dissolved and not visible.
2. Fill the other jug with tap water. Label the jugs A and B
3. Ask one of the students to read Part I of the attached story.
4. Pass out 2 cups to each student and have them label the cups A and B. Have the students pour a small amount of the A jug into their A cup and a small amount of the B jug into their B cup. They should have enough to swallow.
5. Have the students inspect the water and see if they can tell any difference. Have them smell it. Look at it. Let them know that they are going to taste the water but it will not be harmful (VERY IMPORTANT! Tell them NEVER to test something they don’t know what it is. You have set up the experiment and have prepared the test so you know exactly what is in the jugs. Repeat this information!!!!!)
6. Have them predict what they think each will taste like. Which is the normal water?
7. Have them sip from both of the glasses. Did their guesses match what they tasted? Was there a taste to either glass of water? Did it look like there would be?
8. Discuss the following questions:
- What does this experiment tell you about our drinking water?
- What do treatment facilities have to do to water to make it safe and look clean? How would this apply to noticing if there were harmful pollutants in the water?
- Is pollution always murky and brown? Will taste always reveal pollution as it did in this experiment?
- What might happen to a person who consumes drinking water over a long time that contains contaminants they are unaware of? Has this ever happened?
- How do you know your drinking water is safe?
Extension: You can include both sugar and salt waters and have each student have 3 cups.
You can also create differing concentrations of salt and sugar water similar to the previous lesson, “Parts Per Million.” Start with a solution of 10 grams of salt or sugar to 100 milliliters of water. This is 1 part salt (or sugar) to 10 parts water. Create solutions of 1 to 100 and 1 to 500 and 1 to 1000. Students will take turns trying either a distilled water sample or one of the concentrations. They will then try to identify which is the solution. Discuss whether some people have a lower or higher flavor threshold. Relate this to the dangers of water pollution.