Teach Density with Kitchen Science

Author: Joe Rhatigan and Veronika Alice Gunter
Categories: 4th Grade, Science
The simplest concoction is all you need to think twice about what floats and what doesn't. This experiment shows that the simplest ingredients - salt and water - can make for an enlightening chemistry lesson, and will teach your child that science is all around her, all the time!


What You Need
2 clear glasses
Water
2 eggs
Table salt
Measuring spoon



What You Do
Fill one glass halfway with water and carefully place one egg in it. The egg will rest on the bottom of the glass. (Of course it does! An egg is heavy!)
Fill the other glass halfway with water, add 10 tablespoons of salt, and then carefully place the egg in the concoction. The egg will float.
If you add more salt, does the egg float higher?


Why it Works


You can change the density of a substance by heating it, cooling it, or adding something to it. You can test a substance's density by putting something in it and noting how much buoyancy (upward lift) the test item has. Here you test the density of water as a liquid. The density of plain drinking water is low. Salt is a desiccant, which means it absorbs water. So, when you put it in the water, its molecules become bloated with water molecules and sink, creating a highly dense layer of saltwater. The egg floats! This experiment also works with people, but you'll need a lot of salt. (Try the ocean!)

Key Terms for Curious Kids

Density: A measure of how much matter a unit of a substance contains, relative to the volume of the substance.

Salt: A crystalline compound formed by neutralizing an acid with certain bases. Table salt - sodium chloride - is an edible salt with a tangy taste.

Desiccant: A substance that absorbs water and can be used to remove moisture.