Dissolving races:
Objective: Students will demonstrate an understanding that solids dissolve in warm liquids faster than cold liquids. Students will practice making words accurately represent and describe relationships.
Materials:
1. Food colors
2. Gatorade or Kool-aid powdered mix .
3. About 2 gallons of cold water. (Put ice in 2 gallons.)
4. About 2 gallons of hot water.
5. Enough clear plastic cups for everyone in the class.
6. Two clear plastic bottles. (12 oz. or so)
7. Enough sticks for each student to stir.
Your school should already have a source of very hot water to sanitize mops. Bring ice in a cooler if it is not available on your campus.
Focus: Quickly tell the students that we can learn and make predictions if we use what we know and apply it to new situations.
Model: Show how Gatorade dissolves in a cup. It can be declared dissolved when the liquid is rather clear and no more crystals of Gatorade can be seen . Model how the races will be conducted. Create teams of three or four. One team has cups of cold water. The other team has cups of hot water. Fill each cup only half way. Put in only a 1/2 teaspoon of Gatorade in each cup. Who will win the race to dissolve the Gatorade? This race must have impartial judges. The students will quickly recognize the unfair pattern. It may only take a few turns before the class is ready to reach a conclusion. This race is unfair because the team with the hot water always wins. Have the students suggest solutions to make the race fair. Now do the races so that each team has the same temperature water. Change groups and let everyone have a chance to be on a winning team at least once.
Now test their application of what we saw in a new situation: Submerge or otherwise fill the plastic bottles, one hot and the other cold. Have the students take turns comparing and contrasting the two. Allow a few students to hold the two and compare and describe the temperature difference. Do they hold different amounts of water? (No) What is the only difference between these two bottles? (The temperature should be the only difference.) Have the students record predictions into their journals as to what will happen when the color is added to the water. Drop the same number of the same color drops in each bottle and let them stand still. Let the students observe. Have the students suggest what you could write on the chalkboard to summarize what happened and answer the predictions. Keep probing them to state what happened and model how you can write sentences from sentences that are spoken. Show how a writer uses speech to generate ideas for writing. Have them demonstrate that they understand the results in a short quiz:
1. The Gatorade will dissolve in the _______ water faster than the ______water.
Choose: hot ,cold
2. Two men go to a restaurant. One has hot coffee. The other has iced tea. Which man will stir longer and faster to dissolve a teaspoon of sugar? You might choose here to introduce a modest strategy to help solve the question. Draw a picture of the two men. Draw a picture with steam coming out of the coffee cup and condensation on the tea glass. This may help some students to distinguish the parts of the question.
Close: Have the students think and list other ways that we can learn things by making comparisons, making tests and by using language to describe what we experience. At the end let everyone dissolve their own Gatorade or Kool-aid in their own cups and drink it!
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