Summary

The AACT high school classroom resource library and multimedia collection has everything you need to put together a unit plan for your classroom: lessons, activities, labs, projects, videos, simulations, and animations. We constructed a unit plan using AACT resources that is designed to teach Aqueous Solutions to your students.

Grade Level

High School

Objectives

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

• Construct a model of the interactions of water molecules and ions during the dissolving process.
• Explain, on the molecular level, why water dissolves salt.
• Predict the relative solubility of salt in isopropyl alcohol and water.
• Describe how changes in temperature affect the solubility of gases in aqueous solutions.
• Describe how changes in pressure affect the solubility of gases in aqueous solutions.
• Predict how a specific change in temperature or pressure would change the amount of gas dissolved in an aqueous solution.
• Use scientific methods to solve investigative questions.
• Plan and implement investigative procedures.
• Determine which factor influences the rate of dissolution most: temperature, agitation, or surface area.
• Use a conductivity tester in a solution to analyze its electrolyte strength.
• Distinguish between a strong and weak electrolyte.
• Understand the correlation between ion concentration of a solution and ability to conduct electricity.
• Determine the molarity of several different solutions.
• Explain the meaning of molarity while giving reference to the particle concentration in a solution.
• Use models to accurately represent the meaning of molarity.
• Determine the molarity of a solution using the molarity equation.
• Indicate that a precipitate can form from the reaction of two aqueous solutions.
• Understand the components described by a net ionic equation.
• Create particle diagrams for solutions containing dissociated ions.
• Apply their knowledge of solubility rules to the outcome of a chemical reaction.
• Write a chemical equation for a reaction that produces a precipitate.
• Draw accurate particle diagrams for reactions that include aqueous species and formed precipitates.
• Write overall ionic and net ionic equations.
• Predict whether the product of a double displacement reaction will be soluble or insoluble.
• Use experimental evidence to identify an unknown solution.
• Understand that adding a solute to water changes the boiling point of water.
• Know that depending on how much solute is added, the boiling point is effected differently.
• Predict how increasing or decreasing the concentration of a solution will affect the absorption of light through a solution.

Chemistry Topics

This unit supports students’ understanding of

• Solutions
• Solubility
• Intermolecular attractions
• Solute
• Solvent
• Gases
• Concentration
• Temperature
• Pressure
• Conductivity
• Electrolytes
• Mole concept
• Molarity
• Chemical Reactions
• Classification of Reactions
• Indicators of Chemical Change
• Net Ionic Equations
• Solubility Rules
• Particle Diagrams
• Double displacement reactions
• Precipitation reactions
• Boiling and freezing point
• Colligative properties
• Absorbance and transmittance of light
• Visible light and color
• Beer’s Law

Time

Teacher Preparation: See individual resources.

Lesson: 8-12 class periods, depending on class level.

Materials

• Refer to the materials list given with each individual activity.

Safety

• Refer to the safety instructions given with each individual activity.

Teacher Notes

• The activities shown below are listed in the order that they should be completed.
• The teacher notes, student handouts, and additional materials can be accessed on the page for each individual activity.
• Please note that most of these resources are AACT member benefits.

Classroom Resources

• Start this unit by exploring the concept of dissolving with the Basic Modeling of the Dissolving Phenomenon activity, which allows students to explore the process of salt dissolving in water. This resource includes cut-outs of ions and water molecules to help students model the interaction between them and then use their model to make predictions about the relative solubility of salt and isopropyl alcohol. This inquiry activity then has students design an experiment to test their prediction. This resource includes alignment with NGSS.
• If you teach a higher level class, you might choose to use the Advanced Modeling of the Dissolving Phenomenon activity, which has students draw particle diagrams to construct a model of the dissolving process, predict the relative solubility of salt with water and isopropyl alcohol, design an experiment to test their predictions and use claim-evidence-reasoning to build an argument for their model based on evidence. They then apply their model to explain why calcium carbonate is not soluble in water. This resource also includes alignment with NGSS.
• Follow that activity by showing the Solubility Animation to help your students visualize on the particulate level how solubility works. Examples of ionic compounds and a polar covalent compound show that when water is attracted to charged parts, they dissolve, and when they're not attracted to charged parts they stay solid. Have your students refine the models that they created in the modeling dissolving activity after viewing the animation and discussing how and why substances dissolve.
• Then use one or more of the following activities to further explore the vocabulary of solubility and the factors that affect it.
  • Students can explore how changes in pressure and temperature affect the solubility of a gas in an aqueous solution with the demonstration Exploring Gas Solubility. In addition, students will have the opportunity in a post-demonstration reflection activity to practice using their demonstration data and observations to make evidence based claims. This resource includes alignment with NGSS.
  • In the lab, What’s the Solution? students choose a factor, such as stirring, temperature, or particle size that could affect the rate of dissolving. They then design a procedure that can be used to determine how the factor they chose will affect rate of solution, identify one factor as the independent variable and determine how it affects the solubility rate as supported by time required to dissolve the solute.
  • If you talk about conductivity and electrolytes, use the Strong and Weak Electrolytes lab to show students how the conductivity of different common household solutions varies. They can determine the strength of the electrolyte from the brightness of the light on the conductivity diode tester. This resources includes instructions for making your own testers with inexpensive and easy to find. This resource includes alignment with AP Chemistry learning objectives.
• Use the demonstration, What is a 1 Molar Solution? as you move on to the topic of solution concentration and concentration calculations. Students complete short questions prior to the demonstration and then watch as you create one, two, three, and half “molar” solutions using large beakers and plastic mole cutouts. This demonstration supports students’ understanding of solutions, the mole concept, as well as molarity and will help students determine the molarity of different solutions. At the end, you demonstrate how to make a one molar solution of a salt using the correct laboratory technique with a volumetric flask.
  
• Then use the Particle Level Molarity activity to introduce students to molarity at the particle level. Students use their knowledge of molarity by preparing several Kool-Aid drinks, and then apply that information to create representations at the particle level. By the end of this activity, students will be able to explain the meaning of molarity while giving reference to the particle concentration in a solution, use models to represent the meaning of molarity, and calculate the molarity of a solution.
  
• The Kool-Aid lab will give your students practice through calculating the mass of Kool-Aid powder required to make three solutions (C₁₂H₂₂O₁₁) with different concentrations. This lab helps students explain the concept of molarity and calculate the number of grams of solute that are required to produce a given molarity of solution. You can then use the lab, Molarity of a Solution to teach your students how to perform dilutions of Kool-Aid and juice solutions. Students will calculate the amount of solute required to create a solution of a particular concentration and the amount of solvent required to dilute a concentrated solution.
• Finish your study of solubility and solutions with the Preparing Solutions simulation and associated activity to have students practice calculations to determine the molarity of solution, volume of solution, or mass of solute needed. This simulation also includes particle diagrams for each different solution to help students better visualize the solution at the particulate level. Students also gain familiarity with the proper lab techniques for preparing a solution, as they are lead through a step-by-step animated process demonstrating this procedure.
• As you move on to precipitation and the solubility rules, play the Net Ionic Equations Animation to show students a precipitate reaction on the particulate level and understand what a net ionic equation represents for this reaction type. Mixing two aqueous reactants that yield aqueous products and mixing two aqueous reactants that yield a precipitate are both part of the animation.
  
• After viewing the animation, use the Precipitation Reaction demonstration to have your students observe what happens when a precipitate is produced through the reaction of potassium iodide and lead (II) nitrate. A video of the demonstration is included with the resource if you do not have the chemicals available to perform the demonstration. After discussing observations, challenge the students to draw a particle diagram of each reactant and the final mixture.
  
• Then use the Ions in Aqueous Solutions presentation to introduce the solubility rules to your students. In the lab portion of this classroom resource, students mix ionic solutions to determine what combinations form precipitates. They then deduce which ions are responsible for the precipitate and write overall equations and net ionic equations. This lesson includes alignment to AP Chemistry learning objectives.
  
  • If your students need additional practice with the solubility rules and net ionic equations, use the Do it Yourself Color lesson. Your students will use solubility rules to predict whether the product of a double displacement reaction will produce a precipitate, investigate a series of reactions to verify solubility rules, and determine the identity of unknown solutions based on experimental evidence. This lesson includes alignment with NGSS.
• If you teach colligative properties, the Changing Water’s Boiling Point lab will allow your students to explore the concept with a quantitative approach. Students prepare five sodium chloride solutions with different concentrations, bring samples of each to a boil and measure the boiling point, and then use their data to graph the relationship between concentration and boiling point. They then use the graph to calculate the boiling point elevation constant. This resource includes three different student activity sheets. One is a more traditional cookbook lab that provides specific information for preparing the solution. The second gives limited instructions and serves as an inquiry based activity. The third incorporates NGSS-based science and engineering practices.
  
  • If you prefer an activity with ties to everyday life, use the lesson, The Hot and Cold of it All to have your students analyze the effectiveness of different brands of antifreeze/coolant. Students conduct an investigation to examine the freezing point depression in samples that have been diluted with distilled water and determine the specific heat capacities of antifreeze/coolant products as compared to pure water. This lesson includes alignment with NGSS.
• The Beer’s Law Discovered lab is a good resource for those who teach Beer’s Law and the relationship between solution concentration, absorbance, transmittance, and path length. This lesson is written for higher level classes and includes alignment to AP Chemistry learning objectives. We also have two other related lessons in the library that you might want to use with your classes. Both include alignment with NGSS.
  • The Using Color to Identify an Unknown lesson plan utilizes spectrophotometry to identify the wavelength of maximum absorbance of food dye.
  • The Introduction to Color lesson plan allows students to explore the properties related to color and how they vary with changes in concentration.

Culminating Activity

• Students test water samples from a local zoo for the presence of ions to determine why many bird eggs are not hatching in the lab, An Environmental Impact Study. Once the type of ion in the water is determined, students write balanced equations to illustrate their findings and conduct a serial dilution to determine the concentration of the ion in the water sample. The molarity is then compared to known values to determine if the materials in the water are at an unhealthy level.