Divide the class into pairs or groups of three. Give each group two different types of "fun size" candy bars. Each group must measure the mass and volume of both candy bars, then calculate the density of each. As a class, compare the calculated densities of each candy bar. Students may eat the candy bars after the experiment; however, be sure to check with those who might be allergic to chocolate, nuts or other ingredients in the candy.
Prepare 25 mL of water, rubbing alcohol and oil in separate 50 mL beakers. Each liquid has a different density, so when they are poured into one container they will separate. Add food coloring to the liquids so that they can be seen easily. Do not label the containers with the name of the substance. Pour all of the water into a large beaker, followed by the rubbing alcohol and finally the oil. Ask students to observe the liquid's behavior.
Obtain a large glass aquarium and fill it three-fourths to the top with water. Show students unopened cans of Coke and Diet Coke. Ask the students what they think will happen if you place both in the water-filled aquarium, and write their predictions on the board. Place each can in the water. The Diet Coke should float to the top because of the artificial sugars, while the regular Coke should sink to the bottom.
Show students a metal boccie ball and a tennis ball and ask them which they think is denser. The two sports balls look about the same size, and students who have never seen a boccie ball will give mixed responses. Give the objects to one students to hold and ask him which he thinks is denser. The tennis ball is less dense because it is hollow and therefore is not as tightly packed as a boccie ball.