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