Ice is unusual, from a chemist's perspective, in that its solid form is less dense than its liquid form and so it "floats in itself". This behavior is contrasted with t-butanol, which "sinks in itself". In this demo, ice is put into water and observed to float. But frozen t-butanol sinks when it is placed in liquid t-butanol.
Curriculum Notes
This demo can be used when states of matter or density are introduced. It can also be used as a demonstration of the strength of hydrogen bonding in water or anytime the peculiar properties of water are being discussed. Allow about 10 minutes for this demo.
One day of lead time is required for this project.
Discussion
Ice is unusual, from a chemist's perspective, in that its solid form is less dense than its liquid form and so it "floats in itself". This behavior is contrasted with t-butanol, which "sinks in itself". In this demo, ice is put into water and observed to float. But frozen t-butanol sinks when it is placed in liquid t-butanol.
Materials
- 2 glass cylinders
- water
- t-butanol
- ice bucket containing ice and a small plastic container of frozen t-butanol
- small ice scoop
- scoopula
- background box
Procedure
Set the two cylinders in front of the background box. The black background works best. Fill one cylinder about two-thirds full of water and the other about two-thirds full of t-butanol. Add a scoop of ice to the cylinder containing water and add the frozen t-butanol to the cylinder containing t-butanol. The ice should float and the solid t-butanol should sink.
Safety Precautions
Wear goggles. t-Butanol can be an irritant to the skin and eyes. Vapor can irritate the upper respiratory tract, but this is rarely a problem due to its low volatility. t-Butanol is flammable, however, so do not perform this demo near a source of open flame and have a fire extinguisher at hand.