Lab Exercise: Density Rainbow

Joyce Gridley

Bill Davis

Bruce Dillon

7/5/02

Objective:

Construct and calibrate a hydrometer.

Measure the density of an unknown liquid.

Equipment:

  • 100ml Graduated Cylinder
  • Scale
  • Drinking Straw
  • Modeling Clay
  • Steel shot
  • Sharpie pen with fine point
  • Corn Syrup
  • Food Coloring
  • Unknown liquid

Procedure:

Determine Density of Liquid:

Obtain 5-6 solutions that have different concentrations of corn syrup.

Measure the volume and mass of each solution.

Determine the density of each solution.

Construct Hydrometer:

Obtain a straw, bb’s and gum.

Chew gum and cover one end of the straw.

Place 8-10 bb’s into the straw.

Put the straw hydrometer into each liquid.

Allow the straw to come to equilibrium.

Mark the straw the level at which it reaches equilibrium.

Repeat for the other liquids.

Make a Rainbow:

Add food coloring to each liquid. The color frequency of the liquid should increase as the density of the liquid increases. When adding each color be careful to add the colors very slowly and carefully. Otherwise, the colors/solutions will mix.

Determine the density of an unknown:

Determine the mass and volume of the unknown.

Mathematically determine the density of the unknown.

Using the hydrometer measure the density of the unknown.

Predict where the unknown will come to rest in your rainbow.

Drip some of the unknown solution into the rainbow

Liquid / Mass / Volume / Density / Rank / Color
1 / 98 g / 99 ml / 1 / 1 / blue
2 / 127 / 84.5 / 1.5 / 4 / Red
3 / 100.7 / 81.5 / 1.24 / 3 / Yellow
4 / 109.9 / 94 / 1.17 / 2 / Green
5 / 89.1 / 86 / 1.04 / unknown
6
7
8 / Milk
9 / Kool-Aid
10 / Coke Classic

UnknownPredicted location in rainbowLocation in Rainbow

Milk

Kool-Aid

Coke Classic

Questions:

  • Should the viscosity of the colored liquid be considered to be a factor in the determination of the density?
  • Does the temperature of the liquids affect their density? Should all the liquids have the same temperature?
  • Did the unknowns come to rest at the predicted position? Explain.
  • Can your Rainbow tube be used to determine the density of a solid? Explain.
  • List at least one source of possible error in the execution of this exercise.
  • List at least one way you would improve upon this exercise.