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Objective

Students will learn about density.

Class Arrangement

Arrange the class into small cooperative group.  A good size is four.  One member of the group should be assigned the role of foreman or leader, and be responsible for coordinating the group’s effort.  The next member should be responsible for gathering and care of equipment.  The third member is the recorder who will write, record, and keep all written material organized.  Another member is the reporter, who is responsible for giving the oral report and presentation.

Materials

Per group of three or four students:
2 glass beakers, hot plate, water, paper towel, and food coloring

Procedure

1. Gather equipment.
2. Place cold water in a clear beaker.
3. Place several drops of food coloring into the beaker. (Note how the color spreads in the cold water.)
4. Place the other beaker with water on the hot plate.
5. Heat the water until it almost boils (if it boils let it cool enough so that it is not bubbling.
6. Place several drops of food coloring into this beaker. (Note how the color spreads in the hot water.)
7. Record findings on lab report sheet (one per group).
8. Report findings to class.

Students will report their findings to the class.
Students will complete one lab report sheet per group.

Conclusion

Teacher will explain that air and water react in the same way when heated because they are both fluids.  When air is heated the molecules travel around rapidly, causing fewer molecules to occupy the same space.  If there are fewer molecules in the space, the density will be less and this is what causes a hot air balloon to rise.