Going for Water – Session 2
Conduct this session in the schoolyard.
- Give each student the "Going for Water" Lab Sheet PDF • Word and a clipboard (if available). The class will also need one calculator and all the other listed materials except dictionaries.
- Explain that in this experiment, the students will determine how much time it would take to haul all the water needed for a day's use. To begin, students must weigh different volumes of water in order to choose the optimal sized container in which to carry their water.
- Show students an empty quart container, and have them predict how much that volume of water will weigh. Choose three volunteers. Have the first volunteer fill the quart container with water. Have the second stand on the bathroom scale—first holding the quart of water, then without the water. (When standing on the scale with the water, one must hold the container close to the body to get an accurate measurement.) Have the third volunteer find the difference between the two weights; the answer will be the weight of the water. Students can record the actual weight of a quart of water.
- Repeat step 3 with the other volume containers in the order they are listed on the lab sheet: 5 gallons, cup, gallon, half gallon, and pint. (Let the students use the bathroom scale when weighing the cup of water; they should discover that the balance is needed to weigh such a light container.) As the students proceed through the list, encourage them to use the data they have gathered so far to try to make increasingly accurate predictions.
- Have students list the volumes in order from least to greatest on their lab sheets and look for patterns to reinforce knowledge of measurement. (Weights should double from each of the first five volumes to the next.)
- Discuss which would be the best volume of water to haul (i.e., one that is large enough to be a significant portion of a day's worth of water but not too heavy to carry 50 yards.) Hopefully students will choose the gallon!
- Position the 30-gallon trashcan, fill it with water, and place a traffic cone beside it. Choose six students to help measure the 50 yards from the trashcan. Hand out the five yardsticks to the first five students. Instruct them to begin at the traffic cone and lay their yardsticks end-to-end in a straight line. Ask the rest of the class to call out the number of yards measured with each laying of a yardstick ("Three yards!"). Direct the sixth helper to put a finger down at the end of the fifth yardstick to mark the spot while the yardsticks are moved. Then have the five pick up their yardsticks and put them down again, this time starting from where the sixth helper has his or her finger (and the class called out "Five yards!"). Continue until 25 yards have been measured, and place the other traffic cone there to mark it. Ask students how many yards there are in a path beginning at the first cone proceeding to the second cone and back to the first (25 + 25 = 50 yards).
- Organize the students into the same groups from Session 1, and give each group a stopwatch and a gallon bucket. Direct students within each group to take turns timing each other as they carry containers of water from the trashcan to the traffic cone and back. Explain to students that in order to achieve a realistic sample, they must walk—not run—because running would not be practical when making several trips to haul a day's worth of water. Remind them to record their time to the nearest minute on their lab sheets.