Summary

In this activity, students will view an animation that explores what happens in a precipitate reaction on the particulate level. They will see why writing a net ionic equation accurately represents what happens in these scenarios. An example of diluting a soluble solid, mixing two aqueous reactants that yield aqueous products, and mixing two aqueous reactants that yield a precipitate are part of this animation.

Grade Level

High School

NGSS Alignment

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

• HS-PS1-2: Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
• Scientific and Engineering Practices:
  • Developing and Using Models

Objectives

By the end of this activity, students should be able to:

• Write complete and net ionic equations.
• Identify spectator ions in a reaction.

Chemistry Topics

This activity supports students’ understanding of:

• Net ionic equations
• Balancing equations
• Precipitates
• Solubility

Time

Teacher Preparation: minimal
Lesson: 10-30 minutes

Materials

• Computer and projector with internet access
• https://teachchemistry.org/classroom-resources/net-ionic-equations-animation
• Student handout

Safety

• No specific safety precautions need to be observed for this activity.

Teacher Notes

• All of the animations that make up the AACT Animation collection are designed for teachers to incorporate into their classroom lessons. Intentionally, these animations do not have any spoken explanations so that a teacher can speak while the animation is playing and stop the animation as needed to instruct.
• If you assign this to students outside of class time, you can create a Student Pass that will allow students to view the animation (or any other video or ChemMatters article on the AACT website).
• We suggest that a teacher pause this animation at several points or watch it more than once to give students the opportunity to make notes, ask questions, and test their understanding of the concepts presented. The animation is about two minutes long and moves quickly, so students will likely require pausing or multiple viewings to successfully complete the student activity sheet if you choose to use it. Here are some of the points at which you might want to pause the video to allow students to answer the questions on the activity sheet:

• This animation would be most helpful to introduce the concept of net ionic equations after students have learned about balancing equations, solubility rules, and precipitate (double replacement) reactions.
• The first visuals show water being added to AlCl₃ (s), and when the particulate view is shown, there are H₂O, Al³⁺and Cl^- particles in the test tube. This would be a good place to reinforce or introduce the terms “dissolution,” “dissolving,” and/or “dissociation,” etc. to describe the particles of the soluble ionic compound separating when they are added to water. Then more water is added to the test tube, at which point you can reinforce/introduce the terms “dilution,” “concentration,” “solute,” “solvent,” etc. to describe the relationship between substances involved (AlCl₃, the solute, and H₂O, the solvent).
• The next set of compounds are NaCl (aq) and K₂SO₄ (aq). You could pause the animation around 0:21 and have students predict what the products would be, write a balanced equation, and then determine whether a reaction will actually take place. All of this will appear on the screen. Then it will be shown at a particle level and students will see that the ions mix, but nothing really happens because there are no insoluble compounds that form from that combination of ions. This will then be shown as a complete ionic equation, and then as a net ionic equation where all the ions cancel out to reinforce the idea that no net reaction occurs.
• The final set of compounds is MgCl₂ (aq) and K₂CO₃ (aq). Like the previous example, you could pause the animation around 1:08 to have students predict products, balance the equation, etc. before it is shown on the screen. In this case, a solid precipitate, MgCO₃ (s), forms and a reaction does occur. The complete and net ionic equations are then shown on screen.
• Related classroom resources from the AACT Library that may be used to further teach this topic:
  • Unit Plan: Aqueous Solutions Unit Plan
  • Demo: Precipitation Reaction
  • Lab: Mislabeled Mess!
  • Lab: Ions in Aqueous Solution Presentation