The students in my Science classes have been learning about density. Density is defined as the amount of mass in a given volume.Objects that feel heavier tend to have a higher density. So far we discovered that the density of water is greater than the density of wood, but less than the density of a rock. If we know an object's density, we can determine whether it will float or sink when it is put in water. If an object's density is greater than the density of water, it will sink. If its density is less than the density of water, it will float. Therefore, a block of wood will float on top of water, while a rock will sink.
To apply their new found knowledge, the students participated in a fun activity called the "Floating Eggs Challenge". Each pair of students were given 2 beakers half filled with water, 2 eggs and some salt. They put one egg in one of the beakers half filled with water and observed what happened. The egg sank to the bottom of the beaker. Why? The egg's density is greater than the water's density. Next they added 4 to 5 tablespoons of salt to the other beaker filled with water. After they mixed the salt and water, they added the second egg to the salt water solution. What did they observe? The egg floated on top of the water. Why? Adding salt to the water made the water's density greater than the egg's density.
The last challenge of this activity was to figure out how to get the egg floating on top of the salt water to float in the middle of the beaker of salt water. Several students figured out that they would have to add more water to the salt water to make it less dense. Pictured are Oliver Healey and Zach Munro.