Learning about water density might seem like a relatively boring subject, but it doesn't have to be. You can make water density exciting to your second-graders by incorporating a variety of projects and activities into your lesson plans. After doing the projects, the kids will have had fun and learned something at the same time.
A fun project to introduce water density to your second-grade class is how to float an egg in water. Put a half a cup of water in a clear measuring cup. Carefully place a fresh egg in it. The egg will sink to the bottom of the measuring cup. Start to add one teaspoon of salt at a time and stir. As salt is added and mixed in the water, the egg will rise to the surface. Tell the class how salt in water increases water density, allowing the egg to float.
Ribbons of Water
In the ribbons of water project you will see how different water densities react to one another as well as make a cool effect. In three separate cups of water add three drops of different-colored food coloring. Add 4 tbsp. of salt to one cup and 6 tsp. to another. Leave the last cup fresh water. Fill 1/3 of a beaker with the heavily salted water. Then add the medium salted water and finish with the non-salted water. Show the class that the three colors are floating on top of each other. Explain to them that each color had a different level of density, and those with less density are lighter and sit on top.
Guess the Density
This fun game project can be done in groups or as a class. Fill three or four containers with water and different levels of salt for each container, leave one container with no salt, just water. Show the class different objects like eggs, grapes and pingpong balls. Ask the class to guess which object will float and which will not in each container. Have the class or groups submit their guesses. Add the objects to the containers. Did the class get it correct? Explain to them how salt affects the water's density and weight, and how the weight of the water affects the objects.
Levels of Density
This is a quick way to show pure density to your second-grade class. Talk to the class about density and how it works, how lower density liquids and solids will float but something denser will sink. Pour water into a clear beaker, filling it a third of the way. Slowly pour in vegetable oil, adding another third to the beaker. Before the oil and water can completely separate add honey, filling it the rest of the way. Allow the three liquids to separate completely. Explain to the class why this is and how each substance's weight affects the outcome
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