Summary

In this lab, students will create a solution to observe a chemical change between food coloring in water and bleach. They will also develop the process skills of predicting, observing, and measuring temperature.

Grade Level

Elementary School

NGSS Alignment

This lab will help prepare your students to meet the following scientific and engineering practices:

• 3-5-ETS1-1: Define a simple design problem reflecting a need or want that includes specified criteria for success and constraints on materials, time, or cost.
• Scientific and Engineering Practices:
  • Asking Questions and Defining Problems
  • Analyzing and Interpreting Data

Objectives

By the end of this lab, students should be able to

• Create a solution of water, food coloring and bleach.
• Predict and observe a chemical change.
• Measure and record temperature change.

Chemistry Topics

This lab supports the students’ understanding of:

• Chemical Reactions
• Chemical Change
• Solutions
• Mixtures
• Kinetics
• Reaction Rate
• Data collection
• The Scientific Method

Time

Teacher Preparation: 10 minutes

Lesson: 30-40 minutes

Materials

Per Group:

• 1 bottle of food coloring
• 100 ml of Bleach (place in container to start. Refill as needed.)
• Water
• 1 Eyedropper
• 1 Small jar (The size of a baby food jar)
• Thermometer
• Metal spoon
• Timer
• Other:
  • Disposable gloves
  • Optional: swatches of dark fabric

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
• Do not consume lab solutions, even if they’re otherwise edible products.

Teacher Notes

• Prior to the demonstration students should have had instruction and experience with solutions.
• Understanding the reaction: When the bleach mixes with the colored water the food coloring becomes colorless. This occurs because a chemical in the bleach contains oxygen. The oxygen combines with the chemicals in the dye to form a colorless compound. When you add more drops of food coloring the color seems to disappear because it is surrounded by bleach which reacts with it immediate, causing it to change to a colorless solution.
• To add diversity to the investigation, give each group a different food color. Students will see that different colors will react with the bleach at different rates.
• Students should determine if the rate to react and become colorless in the bleach solution will differ depending on the color.
• This lab was inspired by the resource: “Chemistry for Every Kid: 101 Easy Experiments That Really Work”, written by Janice VanCleave (1989)
• Helpful tips:
  • Prepare materials for pairs of students ahead of time.
  • Don’t assume students know how to operate an eye dropper. Take a moment to demonstrate and have the students practice with plain water.
  • Groups of 2-4 work best in my experience.

• Optional extension, or for those who finish early: Bring in swatches of dark colored fabric. Create a mixture of water and bleach. Using an eyedropper add drops of the solution onto the swatch and observe any changes.
• The photograph shows the water and food coloring solution on the left, and the same solution on the right with added bleach.