Water Evaporation

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Water Evaporation

Postby Jencathen » Sat Feb 27, 2010 6:38 pm

Hi, My name is Jenny and I am helping my 11 year old (learning disabled) child with a project.

His project problem is "Does adding salt or sugar to water affect the rate of evaporation?" We have conducted the experiment 5 times.

He added 100 mL each of water, salt water, and sugar water to graduated cylinders and then measured every day at the same time for 24 days.

His conclusion was that tap water evaporated the quickest.

I am stumped on how to help him come up with the answer of what they are calling the extension section. There are two questions that have to be included on his display board.

1. What did you learn from your experiment? To me this sounds like the same thing as the conclusion, but there already is a conclusion section for the board.

2. How could you use what you learned from your experiment in real life? This one really stumps me because I haven't a clue how he could use this information in real life.

Any pointers to help me answer those two questions would be greatly appreciated.
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Re: Water Evaporation

Postby agm » Sat Feb 27, 2010 7:06 pm

Hi Jenny,

Welcome to the forum, and congratulations to your and your child on finishing the project.

Your two 'extension' questions aren't really standard parts of the scientific method, but they are both things I've asked students while judging science fairs. :) You could ask a teacher for clarification, but I bet this is what they're getting at:

What did you learn from your experiment? Did you learn how to use new tools (e.g. a graduated cylinder or balance)? Did you learn a new technique or theory, like how to calculate concentrations of solutions? What did you learn about how to approach questions or problems scientifically? Did something go wrong that you hadn't planned for? You said that you repeated the experiment five times -- how much variation was there between trials? If you'd only done one, might you have drawn different conclusions?

How could you use what you learned from your experiment in real life? Well, what principles did you use to develop your hypothesis and explain your results? The first thing that comes to my mind is that salt and sugar are both hygroscopic, meaning that they can absorb water from the atmosphere, and that attraction to water could also explain why they 'held on' to the water in the solutions you made. Did you understand before why brown sugar gets hard after it's been open for a while, why there are packets of silica gel in pill bottles, or why people sometimes add rice to salt shakers?

http://en.wikipedia.org/wiki/Hygroscopy

Hope that helps! Let us know if you have any more questions.

Amanda
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Re: Water Evaporation

Postby Jencathen » Sun Feb 28, 2010 8:28 am

Thanks Amanda that was a huge help!
Jencathen
 
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