• Monitor student involvement and note taking during the presentation.
• Provide feedback during group work and practice problems to assess general understanding of terms and use of formulas.
• Collect Solutions Worksheet for individual assessment.

Preparation: Prior to the lesson, prepare the materials for the Supersaturated Solution Demonstration (S-C-9-1_Super Saturated Solution Demonstration.doc). It may be helpful to go through the demonstration once before doing it with the class. The beaker of sodium acetate trihydrate should be covered and cooled by this point. Be careful not to agitate the beaker as premature crystal formation may occur.

Day 1:

Tell the class, “I am going to show you a demonstration of the solubility of sodium acetate. This demonstration will provide an example of some of the many qualities of a solution, which we will address during this lesson.” Ask students to provide a definition of a solution. Collect students’ responses and provide a concrete definition before moving on.

“A solution is a homogeneous mixture of two or more substances of ions or molecules. The substances are either solutes or solvents. For example, salt water is a solution made up of water (solvent) and salt (solute).” Ask the class for other examples of solutions and provide clarification. (Answers will vary.)

Gently move the beaker of sodium acetate trihydrate in front of the class or use a document camera for larger classes. If you are unable to perform the demonstration, refer to the following Web sites for videos of each demonstration.

• http://www.teachertube.com/viewVideo.php?video_id=86887
• http://www.teachertube.com/viewVideo.php?video_id=86134&title=Supersaturated_Sodium_Acetate___Slow_Crystalization

Procedure:

1.      Remove the cover from the beaker of sodium acetate trihydrate.

2.      Using tweezers, take one sodium acetate seed crystal and drop it into the solution.

3.      Watch as crystallization occurs throughout the solution.

Alternative Procedure:

1.      Place about a gram of sodium acetate crystals onto a watch glass.

2.      Gently and slowly pour the sodium acetate trihydrate solution onto the crystals to initiate crystal growth. Continue slowly pouring the solution over the top of the crystal growth to create a column of crystals.

Ask, “Can anyone tell me what happened during the demonstration?” Collect student responses and address questions. “What you witnessed was the result of many aspects of solubility, which is the amount of substance, in this case sodium acetate, that can dissolve in to a particular solvent, in this case water. Other factors play a role such as temperature, amount of solute, amount of solvent, and environmental pressure. This lesson will explore the roles all of these factors play in solubility.”

Show the class the Solubility Presentation (S-C-9-1_Solubility Presentation PowerPoint.pptx). Either project the presentation with a document camera or LCD projector or print copies of the PDF version for each student (S-C-9-1_Solubility Presentation PDF.pdf).

Instruct students to take notes throughout the presentation and write down questions they have. When finished with the presentation, address student questions before moving on.

Day 2:

Hand out copies of the Solubility Practice Questions (S-C-9-1_Solubility Practice Questions and KEY.docx). Ask students to pair with another student to complete questions 1–7. Note: Students are not to work on questions 8–10 at this point. They may use the solubility curve graph (S-C-9-1_Solubility Curve Graph.doc) and their notes to answer them.

Source: http://gcserevision101.files.wordpress.com/2009/02/solubility-curves.jpg

Once students finish answering the questions, collect the answers and review them as a class. Instruct students to fix incorrect answers and review questions they have on the material. See Answer KEY on the resource document (S-C-9-1_Solubility Practice Questions and KEY.docx).

Refer to the Solubility Presentation slide 11. Say, “During the demonstration at the beginning of the lesson, I created a supersaturated solution of sodium acetate and water. The sodium acetate trihydrate solution was made up of 160 g of sodium acetate and 30 ml of water. It was heated until the solute (sodium acetate) dissolved completely into the solvent (water).”

Project the Solubility of Sodium Acetate Graph from the presentation (slide 11) and instruct students to refer to their solubility practice questions. Allow students time to work in pairs to answer questions 8–10.

When finished, review the steps involved to answer these questions correctly. Instruct students to copy down all steps, even if their answers are correct. Address student questions once finished.

Hand out the Solubility Worksheet to wrap up the lesson (S-C-9-1_Solubility Worksheet and KEY.doc). This assignment may be completed in class or given as a homework assignment.

Extension:

• For students who might need additional opportunities for learning, mathematical calculations can be taken out of the lesson objectives. In their place, students can represent relationships between solubility and environmental changes with a series of pictures or graphs where they can alter the axes and direction of the line on the graph. Students can also use arrows to demonstrate the relationships (up: increase, down: decrease).
• Students who may be going beyond the standards can do a research project on minerals. Students research various mined minerals which form out of solutions in the Earth as precipitates. An example is gold (Au). Students provide information on the following:

o   Element/mineral mined

o   Location on Earth

o   Method of mineral extraction

o   Method of formation (process, temperature, solubility, etc.)

o   Uses for the mineral