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Project: Which Dissolves Faster?
Materials: cornstarch packing peanuts, five cups/bowls, water, vinegar, baking soda, salt, cabbage pH indicator because we had it
Explanatory details: We compared the dissolution of cornstarch packing peanuts in five conditions: cold water, hot water, vinegar, baking soda solution, salt solution.
How did it go: Good! The set-up was half of the fun, labeling our containers, stirring the salt and the baking soda, and adding a little purple cabbage juice to the vinegar and to the baking soda to see the color change (and help us remember what was special about those dishes). The packing peanuts started to dissolve promptly enough for the scientist's attention span and we did some more stirring to help them come all the way apart. Hot water was faster than cold water, vinegar was faster than baking soda, and salt water was the slowest of all (hot, vinegar, cold, baking soda, salt, I think, although see below for further comments).
Things we talked about: These special packing peanuts are made to come apart in the water into tiny bits, which is called dissolving. Changing the water can make it go faster or slower.
What Junie got out of it: They float! And then they come apart!
Ideas for older scientists: We did not control for the temperature of our vinegar (room temp) vs our baking soda solution (tap water temp, thus colder, which we know makes a difference), and we dropped our peanuts in one by one rather than simultaneously so some of the dishes had a little jump on others. A more careful scientist would want to pay attention to these things. It's also possible that by a casual eyeball the peanut in the salt water was floating slightly higher than the peanut in the plain water due to the greater buoyancy of salt water, reducing the surface area exposed to the water and slowing the process of dissolving. It might be a good followup experiment to try trapping the peanuts fully under the water with a spoon or something to see whether this affects the result.
Materials: cornstarch packing peanuts, five cups/bowls, water, vinegar, baking soda, salt, cabbage pH indicator because we had it
Explanatory details: We compared the dissolution of cornstarch packing peanuts in five conditions: cold water, hot water, vinegar, baking soda solution, salt solution.
How did it go: Good! The set-up was half of the fun, labeling our containers, stirring the salt and the baking soda, and adding a little purple cabbage juice to the vinegar and to the baking soda to see the color change (and help us remember what was special about those dishes). The packing peanuts started to dissolve promptly enough for the scientist's attention span and we did some more stirring to help them come all the way apart. Hot water was faster than cold water, vinegar was faster than baking soda, and salt water was the slowest of all (hot, vinegar, cold, baking soda, salt, I think, although see below for further comments).
Things we talked about: These special packing peanuts are made to come apart in the water into tiny bits, which is called dissolving. Changing the water can make it go faster or slower.
What Junie got out of it: They float! And then they come apart!
Ideas for older scientists: We did not control for the temperature of our vinegar (room temp) vs our baking soda solution (tap water temp, thus colder, which we know makes a difference), and we dropped our peanuts in one by one rather than simultaneously so some of the dishes had a little jump on others. A more careful scientist would want to pay attention to these things. It's also possible that by a casual eyeball the peanut in the salt water was floating slightly higher than the peanut in the plain water due to the greater buoyancy of salt water, reducing the surface area exposed to the water and slowing the process of dissolving. It might be a good followup experiment to try trapping the peanuts fully under the water with a spoon or something to see whether this affects the result.
