Density of Ice in Water vs. Rubbing Alcohol(Allison Shiff)

Questioning Script

Prior knowledge & experience:

Students already know from experience that ice floats on liquids such as water, soda, juice.

Root question:

“Predict where the ice will go when I put it into the liquids.”

Target response:

"Its going to float on the top of the liquid!"

MOVIE:

What is the correct answer

The ideal response would be that it depends on the density of the liquid it is put into.

Common Misconceptions:

Common misconceptions are that ice ALWAYS floats to the top of liquids. Students at this point do not realize that liquids are not all the same density. So an object may be less dense than the fluid it is in and therefore float on top of one liquid but be denser than a different fluid and sink in another.

SUNKEN ICE CUBES

Kids tend to jump to conclusions when things appear to be identical. Fill one beaker with plain water. In another beaker, place alcohol (rubbing alcohol from the drug store is fine but any other alcohol will work). The beakers will look essentially identical. Place an ice cube in the beaker with water. The ice cube floats. Put an ice cube in the beaker of alcohol. The ice cube sinks. The ice floats in the water because the density of the ice is.9000 g/ml and the density of the water is 1.000 g/ml while the density of the rubbing alcohol is .800 g/ml

Photographs

References

Reference 1 NSTA Pathways to learning - How to teach the lesson

Reference 2 Everyday Chemistry - Why does ice float?