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ACTIVITY in Observations, Physical Change, Mixtures. Last updated October 14, 2019.

Summary

In this activity, students will create and interpret particle diagrams that represent elements and compounds at the molecular level. They will also describe the process of dissolving and create particle diagrams that represent mixtures at the molecular level.

Grade Level

High school

Objectives

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

  • Understand mixing.
  • Use macroscopic observations to explain what happens on the microscopic level.

Chemistry Topics

This lesson supports students’ understanding of

  • Mixing
  • Particles
  • Particle diagrams

Time

Teacher Preparation: 1 hour first time, 15 minutes after initial set up
Lesson: 1 class period

Materials

  • 12 glass tubes 30-cm long and 0.5-cm inner diameter (for students)
  • 24 corks or stoppers to fit the glass tube
  • Glass tube (3 m x 2 cm)
  • 2 corks or stoppers to fit the large glass tube
  • 24 beral thin stem pipets
  • 12 small beakers or cups
  • 1 L of water
  • 1 L of isopropyl alcohol (70% or 90%, from the store)
  • Food coloring
  • 1 large culture tube with screw top
  • Aquarium gravel
  • Sand

Safety

  • Always wear safety goggles when working with chemicals in a lab setting.
  • When using alcohol, keep it away from an open flame.
  • 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

For the Student

Lesson

Purpose

Create and interpret particle diagrams, which represent elements and compounds at the molecular level. Describe the process of dissolving and create particle diagrams that represent mixtures at the particulate level.

Materials

  • Glass tubes 30-cm long and 1.5-cm inner diameter
  • 2 corks or stoppers to fit the glass tube
  • 2 Beral thin stem pipets
  • Beaker or cup
  • Blue liquid
  • Yellow liquid

Procedure

  1. Cork one end of a glass tube. (Yes, it is glass so be careful!!)
  2. Fill the tube about half way with the blue liquid.
  3. Completely fill the rest of the tube with the yellow liquid. Make sure you have a distinct blue layer and a distinct yellow layer. Avoid mixing the two liquids by slowly pouring the liquid down the side of the tube.
  4. Place the corked end firmly on a hard surface and cork the open end so that no bubble forms.
  5. Firmly holding both corks, begin turning the tube back and forth to mix the liquids. For the first few turns, hold and exert pressure on both corks to avoid “eruptions.” Continue to mix the liquids until they are completely mixed and the liquid is green.
  6. If bubbles appear during this mixing, empty the tube and repeat the procedure. Do not repeat the experiment more than three times.
  7. Record your observations and explain your observations. Include a particulate model with your explanation.

Conclusion

Use a particle diagram to explain what happened in this activity.