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Postby evianna » Wed Dec 05, 2007 7:43 pm

HI, my daughter is almost completed with her project. She is in third grade and her hypothesis is that an egg will float in the ocean waters of the Gulf of Mexico. Now, she also tested tap and pool water. The pool uses a salt generator. She is using the other water to test how much table salt is needed to float the egg. We used intervals of 30 milliliters in each of the three glass containers until the egg floated. I could use the water as variables, controlled or uncontrolled? The temp was different in each glass. I looked up the temp of the ocean by logging onto NOAA. What else should she include?
Also, for some reason, the catagories are Earth, LIfe, or Physical Science.
Which cat. does this experiment fall under? thanks for all your help.
Sarasota girl
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Postby EmilyDolson » Thu Dec 06, 2007 12:06 am


Great project idea! I wish I could have thought of something that interesting in third grade! It sounds like the salinity of the water is her independent variable, because it is the variable that she changed to produce each result. Temperature will definetly have an effect on the buoyancy of the egg and the salt-holding capacity of the water, so, in an ideal world, it would have been held constant, making it a controlled variable. Preferably, it would have been at the temperature of the water in the Gulf of Mexico (looking it up on NOAA was a great idea, by the way). However, if it is too late to change this, it will probably be okay, especially for a third grade project. Unless the temperature difference was extreme, the effect of it is likely to be fairly negligeble. If she recorded the temperatures, she should note them in the write-up, as well as the temperatures in the Gulf of Mexico. Otherwise, she can just note that there was a difference, and mention the effects this could have had.

As for the catagory, that depends a lot on the exact description of each one. Without being able to read them, I would suspect that it belongs in earth science, because the intention is to explore a non-living aspect of a natural ecosystem. It would also be possible to make a case for putting it under physical sciences, especially if there is a strong focus on the physics behind density and why the egg floats, but it sounds like that would be missing the main point, which seems to be to model the Gulf of Mexico.

I hope that helps! If you have more questions, feel free to ask.

Good luck with the project!

- Emily
Reach for the stars and, if you miss, grab the moon!
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Postby Craig_Bridge » Thu Dec 06, 2007 5:58 am

Try a search on this site for previous investigations using "floating egg" and "bouyancy egg" and you should find a few threads that might help explain some potential issues.
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Postby evianna » Thu Dec 06, 2007 12:56 pm

Thanks Emily for your reply. I can still use the temperature for the pool and tap water.
Because my daughter is in 3rd grade, we aren't focusing on buoyancy. She is not studying buoyant force at this time. She was curious to see if the egg would float in the ocean and then she wanted to test pool and tap water. I'm just trying to help her get this together without becoming too complicated.

Thanks for all your help!!!!
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