chemical solutions written on a chalkboard

Everything You Need to Know About How to Teach Chemical Solutions

Reading Time: 5 minutes

Do You know what I like about solutions? Everyone has prior experience with them, and you can rely heavily on their basic understanding of solutes and solvents. I discuss making kool-aid, lemonade, tea, chocolate milk, etc. 

Our students have a lot of experience with solutions; now we just need to sprinkle in some science. And just like everything, we need to quantify it with calculations. If any of your students move on to careers in chemistry, this is what they’ll be doing a lot of- making stock solutions and diluting them. Solution-making is a skill they’ll need to master. 

Because solutions are so important, this unit provides a GREAT opportunity for a lab practical! Get them in the lab and make it count. You don’t have to be brutal, but they’ve been measuring liquids for a while now; they should be pretty good at it. 

Chemical Solutions Lesson Plans

Total Duration: 10-14 days

Note: a day refers to 45-50 minute periods.

Topic & TimelineTasksDescription
Parts of a Solution

1 day		Parts of a Solution NotesWe start off with a discussion of “what exactly is a solution?”. You can set up several beakers and flasks and physically make solutions to show them that the basic concept is simple- we need to learn new vocabulary. We spend time identifying various solvents and solutes. 
Solution Concentration

2 days		Molarity Notes

Molarity Lab		Now that we know what a solution is and how to make one, we can quantify our solutions with Molarity (if you want to calculate colligative properties, you’ll want to teach molality as well). 
After teaching molarity and practicing some calculations, have your students make a solution of known molarity from start to finish. I’ve linked my OLD molarity lab for reference. I ask each group to make 100 mL of 2M or less. They record their work on a separate sheet of paper and then make the solution. It’s not super flashy, but they now know how to determine how many grams of solute are in a solution. 
Alt Lab: pHet Molarity
The Solution Process

1-2 days		Solubility Notes

Solubility Curve Practice		Now we move on to solubility- will every solute dissolve? It depends on the nature of our solvent. 
We discuss water as the universal solvent but also the exceptions to that rule. I pull out water and oil and see they are not miscible. 
I have my students look at the back of their Periodic Tables to discover the solubility rules that have been there ALL YEAR. Now we put them to good use! These are VERY simplified rules. 
I have a set of laminated solubility curves that we then practice with. I give them a set of conditions, and they identify the solid. Then I change these conditions to see if it continues to be soluble. Solubility Curves can be a bit intimidating, so the fact that they can use dry-erase markers and “play” makes them a little less scary. 
Dilutions

2 days		Dilutions Notes + Practice

Serial Dilutions Lab
Alt Lab: pHet Concentration		Depending on your timeline, you may want to move dilutions up right after the molarity lesson. I like to break it up, so I wait until we know more about solutions. 
They’ve seen this equation. “Where have you seen this equation? What does it look like?” Someone will say, “Gas laws!” and they are 100% correct. Replace P with M, and voila! This will also help later when discussing equilibrium (in this class or AP chem). 
The serial dilution lab can be done as a demo, as you’re just using colored water and slowly diluting it so they see the color getting lighter. I will attempt an acid-base dilution with a universal indicator this year to get a nice rainbow. If it works out, I’ll update you!
Ions in Aqueous Solutions

1-2 days		Electrolytes Notes
Electrolytes Lab

Optional: Net Ionic Equations Notes		Diving deeper into the solution process, we can link colligative properties to electrolytes. You can also move this topic to earlier in the unit, may to day 2. 

Electrolyte Lab
Students make a lot of little solutions and then use conductivity testers. Two lights? Strong. One light? Weak. No lights? Non-electrolyte. 

If you don’t have conductivity testers, I suggest using this pH pHet Sugar + Salt Solutions Simulation.

As some possible enrichment, you can introduce Net Ionic Equations. What happens when you dissolve a solute? Students can determine if a solute will dissolve using their solubility rules and then write the net ionic equations. I also like to discuss why this is useful in the industry. Every step of the way, companies like to save money. If the reactants they’ve been using are expensive, they can look at the net ionic equation and maybe swap something out for a more affordable ingredient. 
Colligative Properties

1-2 days		Icy Roads Discussion

BP Elevation + FP Depression Lab

Ice Cream Lab		Now that we know about solubility and what happens to a salt when it dissolves, we can talk about WHY the ice on winter roads melts when you salt them. You’re decreasing the freezing point, friends. 

What about adding salt to a pot of water on the stove? You are increasing the boiling point! 

The BP Elevation + FP Depression Lab is very straightforward:

Part 1: BP Elevation 
Trial 1: boil 1L water
Trial 2: boil water with 5 tsp NaCl
Trial 3: boil water with 10 tsp NaCl

Part 2: FP Depression
Trial 1: 1cup ice + 200mL water
Trial 2: 1cup ice + 200mL water + 1 tsp NaCl
Trial 3: 1cup ice + 200mL water + 2 tsp NaCl

**Part 3: Vapor Pressure
You can try vapor pressure if you have pressure sensors. I’ve never been able to test this, so I don’t have a good option for you. 

Ice Cream Lab
If your school allows you to feed your kids, this is a FUN one. I’ve linked the one I used way back when… before I worked at a school that banned food (in class, not the lunch room). It has a little more math, but you could always take that out and look at the temperature the ice got down to to freeze the ice cream (about -11𝆩C)
Review

1 day		Solutions Vocabulary Review

Study Guide		Go about your typical review. If you made your own set of laminated solubility curves, you could pull those back out. 
Assessment

1-2 days		Test and/or Lab PracticalI like to do a lab practical for my solutions assessment. I give students a specific solution they have to make using a solute and solvent. I offer both ionic and covalent compounds. I try to provide them with compounds that are colored so the dilutions are easier to see, but you could always have them add a couple of drops of food coloring OR use Kool-Aid. 
Using the solution they’ve made, they then complete a set of serial dilutions.  I inherited some colorimeters this year, so I’ll add that to this part of their assessment to see just how good their dilutions were.  

Then they test their solutions with the conductivity tester. Based on their results, they’ll draw particle diagrams of their solutions. These diagrams should include their concentration in relation to water molecules and charges (strong vs. weak vs. non). 

Alternate Idea: If you want to include solubility curves in this lab practical, you could make many of the salts available and have them determine the temperature required to make their desired molarity of a specific salt, and then make it. I’ve never done it this way. Instead, I give a short quiz on topics I can’t “test” in the practical. This could be a great addition, though. Let me know if you try it!

Further Reading

The Chemistry Particle’s Guide to Teaching High School Chemistry, The Chemistry Particle

Chemical Solutions Notes Bundle, TeachersPayTeachers

Classroom Resources: Solutions, American Association of Chemistry Teachers

A cross-age study on the understanding of chemical solutions and their components, International Education Journal

Solubility, Stoichiometry and Non-stoichiometry, ChemEdExchange

Freezing Point Depression Near Body Temperature with Eicosane and Azobenzene, ChemEdExchange

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