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Observing a Chemical Reaction Mark as Favorite (23 Favorites)

LAB in Observations, Physical Properties, Chemical Change, Physical Change, Chemical Change, Temperature, Exothermic & Endothermic. Last updated July 14, 2024.


In this lab, students will practice making careful observations and measurements while witnessing a chemical change.

Grade Level

Middle and High School

NGSS Alignment

This lab will help prepare your students to meet the performance expectations in the following standards:

  • MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
  • Scientific and Engineering Practices:
    • Developing and Using Models
    • Analyzing and Interpreting Data


By the end of this lab, students will be able to:

  • Differentiate between a chemical change and a physical change.
  • Identify when a chemical change takes place with supporting evidence.

Chemistry Topics

This lab supports students’ understanding of

  • Chemical changes
  • Observations
  • Physical changes


Teacher Preparation: 10 minutes

Lesson: 20 minutes


For each group:

  • Beaker
  • CuCl2
  • Aluminum foil
  • Thermometer
  • Water
  • Stirring rod


  • Safety goggles should always be worn when working in a lab.
  • Copper(II) chloride is a skin irritant. Avoid skin contact with this chemical.
  • Use caution when working with the thermometer.
  • 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.

Teacher Notes

  • Students practice some of the skills learned in a typical first chemistry unit—new vocabulary, scientific thinking, submicroscopic interpretation of macroscopic events, making observations.
  • This simple experiment sparks an interest in what students will study in the course.
  • If time allows, cut the aluminum foil into 3 inch by 3 inch squares in advance.
  • Students will often confidently declare that “rust is forming”. To help them answer the post-lab questions correctly, refer back to the original chemical reaction. Ask them if they think the color comes from copper, aluminum, or chlorine.

For the Student


A chemical reaction or chemical change happens when substances combine to form new substances. Four signals of a chemical change include the release of a gas, the formation of a solid, an energy change (usually in the form of heat or light), or a color change. When several of these signs are present, a chemical reaction has probably taken place.

In this experiment, you will see physical and chemical changes. A solution of copper(II) chloride will be mixed with a ball of aluminum foil. Throughout the experiment, you will be asked to record observations. Remember that observations are statements of fact, things that can be detected with your senses. For example, “Steam is released” might be better stated as “a gas is released” unless you know for certain that water is formed in a chemical process.


  • Wear an apron and goggles when performing this experiment.
  • Copper(II) chloride is a skin irritant. Avoid skin contact with this chemical.
  • Use caution when working with the thermometer.


  1. Obtain a spoonful of copper(II) chloride and a small piece of aluminum foil. Record your observations.
  2. Measure 25 mL of water and pour into a beaker. Without stirring, add the copper(II) chloride to the water in the beaker. Record your observations.
  3. Use the glass stirring rod to stir the mixture until the crystals are completely dissolved. Record the temperature of the mixture. Record any other observations.
  4. Loosely crumple the aluminum foil and place it into the solution. Use the stirring rod to stir the mixture. Record the highest temperature reached. Record other observations.


Step 1
Step 2
Step 3
Step 4


  1. Identify the changes that occurred in these steps of the procedure as physical or chemical:
    • Step 2    physical    chemical    (circle one!)
    • Step 3    physical    chemical
    • Step 4    physical    chemical
  2. For the chemical change(s), what evidence supports that a chemical change occurred?
  3. The experiment began with copper(II) chloride and aluminum. Use the key below to draw the particles present in these substances. Draw three particles for each substance:
  1. List two observations from your data table that are qualitative and two that are quantitative:
  2. List two physical properties of copper(II) chloride and aluminum:
  3. The experiment began with copper(II) chloride and aluminum. What substances do you think were present in the beaker at the end of the experiment?
  4. Use the key in #3 to draw pictures of the particles you think are present at the end of the experiment. If you need additional symbols, be sure to define them.
  5. How could you test this hypothesis?