Explanation of the activity:

This demonstration helps to show that our bodies lose water while doing everyday activities and how it is important to drink water to stay hydrated.


Take a 4” x 6” sponge and draw a man on it, like the outline of a gingerbread man. Cut the sponge-man out using scissors. Sit the sponge out for four days before using it in the lesson, so that it is dried out and stiff to begin the lesson.

Note: This demonstration can conclude after several hours or several days, depending on how long it takes the sponge to completely dry out. Therefore, it is important that enough water is added to the sponge so that information can be collected at two time periods. Students should observe Sponge-Bobby in the wet stage and in the dry stage.


  1. Gather students around a table with a sponge, cup of water and plate.
  2. Introduce them to Sponge-Bobby and explain that Sponge-Bobby is like us, because he is healthiest and feels his best when his body is full of water.
  3. Pass the dry sponge around the class and discuss the texture of Sponge-Bobby. Emphasize that in this state, Sponge-Bobby is dehydrated and doesn’t have any water.
  4. Add water to Sponge-Bobby until he is full of water.
  5. Have students write a hypothesis (guess) about what will happen to Sponge-Bobby. Have students keep observations in their journals.
  6. Let Sponge Bobby sit until he is once again dry.

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