Summary

In this lab, students will follow a laboratory procedure that instructs them how to heat a small sample of copper(II) sulfate pentahydrate. Students will make observations in order to determine if a chemical or physical change occurs.

Grade Level

Middle School 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:
  • Analyzing and Interpreting Data
  • Engaging in Argument from Evidence

Objectives

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

• Differentiate between a chemical and physical change, identifying examples of each.
• Justify a conclusion based on experimental results.

Chemistry Topics

This lab supports students’ understanding of

• Physical Change
• Chemical Changes
• Observations
• Molecular Structure

Time

Teacher Preparation: 20 minutes

Lesson: 50 Minutes

Materials (per group)

• 4-5 grams Copper (II) Sulfate Pentahydrate (1-2 crystals)
• Test tube
• Test tube holder
• Test tube rack
• Bunsen Burner
• Striker/Matches
• Safety Goggles
• Scoopula

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.
• Always use caution around open flames. Keep flames away from flammable substances.
• Always be aware of an open flame. Avoid reaching over the open flame, tie back hair, and secure loose clothing.
• If using a match to light the Bunsen burner, be cautious with the flame.
• An operational fire extinguisher should be in the classroom.

Teacher Notes

• For lab preparation, it may be best to place a few crystals of Copper(II) Sulfate Pentahydrate in small weight boats for each lab group. This will decrease the time needed to obtain supplies.
• Students should set up and obtain all supplies prior to getting the crystals.
• Dispose of crystals per your school’s chemical cleanup procedures, or allow wet crystals to re-crystallize. Use of distilled water to rehydrate in the lab activity is needed if reusing the crystals.
• Warm up:
  • Ask students to identify the difference between a physical and chemical change. This will include a discussion of clues that show a chemical change has occurred. These could include bubbling (gas production), precipitate formation, energy change (exothermic/endothermic reactions, light production) and production of a new substance.
  • Students could be asked to first brainstorm their ideas individually and then discuss their thoughts with a partner.
  • Engage all students by compiling all student contributions on the board/smartboard/classroom display.
  • Examples of Physical/Chemical Changes may include:
    

    Physical Changes	Chemical Changes
    Changing the size of an object Phase Changes Dissolving substances (salt into water) Changing the color of an object with a dye/marker Breaking an object into pieces	Burning/Combustion Mixing acid and base Digesting food Cooking meat Baking bread Oxidation of metals

  • Define a hydrate: compounds, typically crystalline that weakly attract water molecules and retain them within the crystalline structure.
  • Show the image of Copper Sulfate.
• Optional Extension:
  • View the YouTube video: Hydrated Ionic Compounds. The follow up lecture is very dependent on how you arrange your curriculum. If this activity follows basic naming of ionic compounds, it will work nicely to examine how hydrates are named.
  • Lectures or review of content could be as simple as discussing the type of change being physical (the removal of water molecules from a crystal), to a detailed examination of the number of moles of water removed from a sample of the compound.