Ask your audience the question: “Will this can of regular soda float or sink in the bucket of water?” After gathering everyone’s answer, place the can of regular soda in the water and notice that it sinks to the bottom.
Pick up a can of diet soda and pose the same question. Be sure to point out the fact that the cans are exactly the same size and shape and contain the same amount of liquid (compare the number of milliliters—probably 355 mL). Place the can of diet soda in the water. It floats! Wobble the can from side to side to show your audience that there are no bubbles trapped under the bottom. It still floats. Why?