Serial Dilution of CuSO4 and Changing the Value of Paint
Teacher: Christine Smith
School: Hubbard High School
Suggested Grade Level: High School
Title: Serial Dilution of CuSO4 and Changing the Value of Paint
Subject: Chemistry
Time: 30 minutes
Index:
Background
Objectives
Materials
Procedure
Assessment
State Goals and Chicago Academic Standards
Background
CuSO4 (copper sulfate) makes a blue solution in water. As the concentration of dissolved particles decreases, the value of the color becomes lighter because there are fewer particles to reflect the light. When working with paint, artists may change the value of a particular color by adding white to make it lighter or black to make it darker. Since black absorbs all wavelengths and white reflects all wavelengths, the value of color perceived by the eye varies according to the amount of light waves it receives.
Objectives
- Relate solution concentration and saturation to color
- Compare methods of changing value and color intensity with paint solutions
Materials
Poster paint, brushes, paper
CuSO4 5H2O
Balance
Graduated cylinder
Test tubes
Pipettes
Stirring rods
Volumetric flask
Procedure
Part I – Ask students to
1. Make 100.0 mL of a 0.5 CuSO4 molar solution in a volumetric flask.
2. Using a pipette, transfer 1.0 mL of this solution to a 10.0 mL graduated cylinder and add distilled water up to 10.0 mL. Put into test tube.
3. Now take 1.0 mL of this second solution and transfer it to another 10.0 mL graduated cylinder and add water to make a 10.0 mL solution.
4. Continue transferring 1.0 mL of each solution and diluting it four more times or until the solution is colorless. This is called serial dilution.
5. Show calculations for making the original solution, and calculate the molarity of each of the other six solutions.
Part II – Have students
1. Using poster paints, paint a square in the same hue as the CuSO4 solution.
2. Make seven squares of paint successively lighter by adding small increments of white paint to the blue paint.
3. Make seven squares of paint successively darker by adding small increments of black paint to the blue paint.
Assessment
Evaluate students on how they use equipment to make serial dilutions and on their calculations in determining molarity. Ask students to compare changing the concentration of a solution with changing the value of a hue.
State Goals and Chicago Academic Standards
Chemistry
State Goal 12/Chicago Academic Standard C
Chicago Framework Statements 1, 2, 4
Conceptual Statement–Chicago Program of Study
The most commonly used unit of measurement of concentration is molarity (moles/liter). Molarity is used to express the degree of acidity/basicity of an aqueous solution in terms of hydronium ion concentration.
Supporting Ideas
A solution is a homogeneous mixture of a solvent and a solute. It is described in terms of molarity (the number of moles of solute per liter of solution).
