# Factors that Affect Solution Formation

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## Objective

Students will be able to describe the factors that effect solution formation through taking notes and performing an activity.

#### Big Idea

Temperature, stirring, surface area, and pressure affect the solubility of a solute in a solvent when forming a solution.

## Introduction

In this lesson students continue to think about solubility through graphing solubility curves for two substances and learning about the factors that affect solubility through notes and an activity.

• This lesson loosely aligns with the Next Generation Science and Engineering Practice 1-5: Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.  It does so because students are learning the factors that affect solution formation which is very similar to the factors involved with reaction rates.
• This lesson aligns with the Next Generation Science and Engineering Practice 4: Analyzing and Interpreting Data It does so because students are graphing data on solubility and then analyzing their data.
• This lesson aligns with the Next Generation Crosscutting Concept 3: Scale, Proportion, and Quantity.  It does so because students are learning about solutions and how they are composed of different proportions of substances.

For this lesson each student needs 3 m&m's.

## Engage

30 minutes

To begin this lesson I give students an opportunity to review what we have already learned about solutions in terms of solubility and solubility curves.  Solubility curves is a topic that many of my students have a hard time understanding so this activity gives them another opportunity to work with this difficult concept.

• I begin this portion of the lesson by passing out the graphing solubility practice paper.
• I then have students take several minutes to read over the background information to themselves.
• After students seem to be done reading I tell them that we are going to start to work on the graph together and then they will be answering the questions on their own.  I make sure to help students set up the graph, especially those that had a hard time graphing boyle's and Charles' laws in the last unit.
• This includes going over how to set up the axis, how to label the axis, how to title the graph, and how to plot the data.
• Here are several videos that show how I help students with setting up their graphs.
• In this first video I explain to students what they will be doing and how to determine the x and y axis.
• In this second video I explain to students how to set up and scale their axis.
• In this third video I explain to students how to write down information about their graphs.
• After students have started to graph I have them complete the graphs on their own and then answer the questions about the graph.  I tell them that if they are stuck with the questions that they should go back and read the background, look back at their notes from the previous lesson, and/or to review last night's homework.
• Many students struggle with solubility curves including reading the graph and understanding what it means to be saturated etc.  Because of this I make sure to walk around and help students as they are working.
• Here is a key of what the final graph and answers should look like.
• This is one example of a student's final paper.

## Explain

10 minutes

During this portion of the lesson I introduce students to the new topic for the day, factors that affect solubility.  I present the new information to students on the PowerPoint while they take notes on the top half of their notes graphic organizer.

• I begin by asking students the question the first slide of the PowerPoint, "If I want to make a substance dissolve in a liquid what could I do?"
• Students usually answer with stirring, or heating it up.
• I then show students the 2nd slide and tell them, "We are going to continue talking about solutions with a focus on 4 factors that affect solubility.  3 of these are for solids, liquids, and gases, and that the 4th one, pressure, is for gases only".
• I then go through slides 3-6 with students while they write down information on their graphic organizer.  When I discuss surface area I make sure to remind students that surface area is the area on the outside and that to increasing surface area you can chop something up.
• Here is one student's filled in notes
• As a summary of what students just learned and to transition into the next activity I have students watch this Solubility video which summarizes the factors that affect solution formation with some examples.

## Elaborate

15 minutes

To help reinforce what students learned about factors that affect solubility I lead them in a tasty solutions activity.

The goal of this activity is for students to remember the factors that affect the solubility of a solid as temperature, stirring, and surface area.

To begin the activity I show students the last slide of the unit8 lec2 presentation and have them look at the bottom of their notes organizer.

I then explain to them, "We will be doing an activity to help you remember the factors that affect the solubility of a solid.  I am going to come around with some M&M's.  Just let them sit on your paper until we are ready to do the activity together.  As I am walking around, read the instructions for the activity to yourself."

I then walk around and pour M&M's onto students' papers.  Each student needs at least 3.

I then ask students if they are ready to start and have them take the first M&M in their hand.  I put the TimerTools stopwatch timer on the projector and tell students, "we are all going to start together.  When you feel that the M&M is dissolved, then record the time".  For this first trial we are simply going to change the temperature so just let the M&M sit in your mouth.  I then say 3, 2,1 and go.  It takes students about 2 minutes to feel the M&M has completely dissolved. This introduction video shows how I begin the activity with one class.

As students are waiting I help them think about what we are doing by asking questions such as, "what is the solute?  What is the solvent?  What is the solution?"  Here is a video of me questioning my students during the first trial.

After most students are done I say, "okay, now lets do the second trial.  This time not only are we going to increase the temperature, but we are also going to stir."  I then ask students if they are ready and then countdown, start the timer, and have them do the 2nd trial.  This trial takes students about 1 minute.  This movie shows how I do this.

Finally, I have students do the 3rd trial.  I tell students that for this 3rd trial we are going to increase the surface area so we will be chopping up the M&M with our teeth.  Then, I countdown, start the timer, and have students do the 3rd trial.  This one takes them just a few seconds.  This final movie shows how I get students started on this last trial.

As students are completing this last trial I tell them to spend some time answering the questions at the bottom of the activity.  I tell them to try them on their own first, and that if they are stuck then they should work with their table groups.

After almost all students are done (about 5 minutes) I go over the answers with students.  I do this by calling on students to share out their answers.

This is an example of a student's completed paper