Hobbies And Interests
The Experiment
To conduct the simplest version of this experiment, you will need a drinking glass, an egg, tap water, salt and a spoon. Fill the glass with tap water at room temperature and place the egg (also room temperature) in it. The egg will sink. Take the egg out and stir in salt water one tablespoon at a time. See how many tablespoons of salt you must add before the egg floats. This experiment alone, however, is probably not complex enough for a fifth grade project. You should also explore the science behind the experiment and consider some implications of it.
The Science
For a fifth grade project, you should be able to explain mathematically why your experiment works the way it does. This experiments deals with volume and density. Density is equal to mass divided by volume. If an object's density is less than that of the medium that surrounds it, the object will rise. This is why a balloon filled with helium floats: because the helium is less dense than air. This is also why the egg floats in salt water, because adding salt to the water increases its density. You can test this premise with another experiment. Pour one cup of salt into one cup of water and mix it (although it will not all dissolve). The volume of the mixture will be less than two cups, because the two masses when combined take up less volume than separately.
Variations
You can also try some variations on the original experiment. Try mixing a salt water solution dense enough to float the egg in the bottom half of your glass. Carefully pour regular tap water in the top half, do not stir and add the egg. If you do it correctly, the egg will drop through the tap water and float in the middle of the glass. Also, change some of the elements of the experiment. Does adding sugar to the water make the egg float? What about sand? If you use juice or soda or another beverage instead of water, does it make a difference? Does hard-boiling the egg change the results of your experiment (use the same egg before and after boiling)? Form hypotheses on these or other questions and test your hypothesis.
Conclusions
This experiment can be a starting point for you to explore questions about the ocean and about determining the relative density of objects. Do some research about the ocean. What is the concentration of salt in the ocean? Would an egg float in it? Compare the density of other small household objects to that of the egg. How much salt is needed to make different objects float? What about boats? Wood floats on water because it is less dense than water, but iron is not. What is the science behind an iron ship? For a fifth grade project, consider implications beyond the obvious conclusions from your experiment.