I really like this demonstration too because it's easy to set up and you don't need a lot of equipment. All you need is salt water, 2 eggs and 2 containers. Here is what you do: One container is filled with fresh water. The other other container is filled with super saturated salt water (I overdo the salt to ensure I get the proper results). I do not tell my students that the water content is different. I want them to figure it out. Before you place the eggs into the water, have your students make a hypothesis as to what they think will happen. After your class discussion, drop the eggs into the water and make your observations. You will get very different results based on the water content. Check out the video below to see what it will look like. Have fun with this as your students will be amazed!