Rainbow in a Beaker


DESCRIPTION:
Sugar solutions that have different concentrations have different densities; the more sugar in a solution the more dense it is. Therefore less dense solutions can be layered on top of denser ones.

TOPICS COVERED:
- density
- physical change
- miscibility

MATERIALS NEEDED:
- 4 colored sugar solutions (0.974M (red), 1.95M (yellow), 2.92M (green), 3.90M (blue), to make dissolve 15g, 30g, 45g, and 60g in 45mL of water each)
- spoon
- tall skinny beaker

PROCEDURE:
1. Carefully pour the blue solution into the beaker, without spilling any on the sides
2. Holding the spoon so that it is just above the level of liquid in the beaker, carefully pour the green solution down the spoon
3. Repeat step 2 with the yellow and red solutions

ADDITIONAL COMMENTS:
This takes a steady hand and some patience. The sugar solutions shouldn’t be heated to get the sugar to dissolve; they will turn into syrup. The solutions make everything sticky, so have paper damp paper towels on hand. This demo can be turned into a hands-on activity by using small test tubes and disposable pipets. Challenge students to pipet the solutions in without mixing them.

SAFETY:
Safety goggles should be worn at all times.

REFERENCES:
Shakhashiri, Bassam Z. “Layered Liquids.” Science is Fun. Accessed July 7, 2010.
http://scifun.org/HomeExpts/layeredliquids.htm

Handout