Sinking and Floating Soda Cans

Materials: ★☆☆ Easy to get from supermarket or hardware store
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required

Categories: Density and Buoyancy, Food Science and Nutrition

Alternative titles: Regular and Diet Coke Cans in Water, Density Demonstration with Soda

Summary

This demonstration compares the buoyancy of regular and diet soda cans. Regular soda sinks in water because dissolved sugar makes it slightly denser than water, while diet soda floats because it uses a much smaller mass of artificial sweetener. Adding salt to the water increases its density so that even the regular soda can floats.

Procedure

Fill a clear container (at least 4 liters) with tap water.
Gently place a 12-oz can of regular soda and a 12-oz can of diet soda into the water.
Observe that the regular soda sinks while the diet soda floats.
To extend the demonstration, gradually add salt to the water while stirring.
As the water becomes denser, the regular soda can will eventually float, while the diet soda can rises higher and tips onto its side.

Links

Why Do Some Pop Can Float and Others Sink? - Cool Science Experiments Headquarters:

Sink of Float Coke and Diet Coke Experiment - Kids Fun Science:

📄 Regular and Diet Coke Cans in Water - UPenn: https://www.physics.upenn.edu/demolab/manumech/ms9.html

Variations

Try other soft drinks to confirm that brand does not affect the result.
Test plastic bottles, which will sink regardless of sugar content.

Safety Precautions

Handle the large container carefully to avoid spills.
Stir gently to prevent splashing.
Clean up any spilled salt water promptly, as it can be corrosive to metal surfaces.

Questions to Consider

Why does regular soda sink while diet soda floats? (Regular soda contains about 39 g of sugar, making it denser than water, while diet soda contains only a small mass of artificial sweetener, leaving it less dense than water.)
What role does the air space in the can play? (It slightly decreases the overall density of the can but not enough to offset the sugar in regular soda.)
Why does adding salt change the outcome? (Dissolving salt increases the density of the water, eventually making it greater than that of the regular soda can.)
How does this demonstration relate to swimming in very salty bodies of water like the Dead Sea? (High water density increases buoyancy, allowing people and objects to float more easily.)