Science Buddies: "Ask an Expert"

Question Re: Solar powered water desalination -- from Graciela 4th grader
Project: https://www.sciencebuddies.org/science- ... p022.shtml

Since the Science Buddies' idea to change the color of the device bottom to test already tells us the findings, I thought I could test different factors. I have two ideas and am hoping you can pick which one makes more sense.

Idea 1#
When water becomes the "new oil"/scarce, I think there will be companies that will desalinate water for consumption but what if people want tastier water? In this experiment, I will desalinate two different salt water devices; one device will have 3 tablespoons of cherry flavored syrup salt water and other device will have salt water only. Test the rate of evaporation during process and I will compare the water after the process, the purity, the yield and the taste.

Idea #2
Is there a faster way of desalinating water? In this experiment, I will place a solar panel (what kind...tbd) over one of the white colored bottom devices so the sun will hit the panel and heat the device underneath, testing if this will heat up faster and create more water. The other white colored bottom device will be opened to normal sun light. I will compare the two devices.

Hello!

Here are some opinions on your two proposals:
1. You are assuming that the cherry flavoring will evaporate with the water and move into the collection device. This may not be a good assumption. How can you know? You will need to know something about the vapor pressure and boiling point of the flavoring. Also, how will you test the "purity" of the collected solution? If you can test the purity of the collected water, I would suggest just doing that for the 2 options in the original experiment. If one of the colored papers gives you more yield, does the higher yielding device also deliver the same purity? Another simple thing to try would be to add some food coloring and see whether it makes it through the process.
2. I'm not sure what you're planning to do here? Put a solar panel over and completely covering the box? Since heat usually rises, how will this heat the water beneath it? While the panel may collect power, how does it affect the desalination process? This seems like it might be too many variables in one experiment.

I've seen SF projects where the student attempted to make a lens out of plastic wrap and water. What would happen if you poured some water over the top of the plastic wrap? Would it act like a lens? Would it cause the water to heat up more and evaporate faster? Something to think about.

Best, Keith