**Everyone has Problems, but Chemists have Solutions**

Kathy Kreidler Thornridge High School

15000 Cottage Grove Ave.

Dolton, IL 60419

(708) 841-5180 X 2585

**Objectives**:

The student will

1. relate chemical solutions to everyday solutions.

2. define **molarity**.

3. explain how solutions of different molarities are prepared.

**Materials needed**:

Teacher demonstration:

2 packets drink mix table salt, NaCl

2 quart pitcher balance

2 drinking glasses--different sizes beakers--different sizes

labelled reagent bottles of stuffed cloth mole models^{*}
differing molarities one-liter volumetric flask
**Strategy**:

1. Have labelled reagent bottles sitting out on the desk.

2. Following student directions, prepare a pitcher of drink mix, bringing out

the terms **solvent**, **solute**, **solution** and **homogeneous**.

3. Pour some of the prepared drink into two different-sized glasses. Ask the

students to compare the concentration of solution in each of the three

containers. All concentrations are 1 pack/pitcher.

4. Ask how a 0.5 pack/pitcher could be made. Students should realize that the

packet must be opened and the amount desired must be weighed out on the

balance.

5. Point out the reagent bottles and explain that terms such as 0.5M and 3M are

expressions of solution **concentration**.

6. Using a 1 liter volumetric flask, demonstrate how to make a 0.1M solution of

sodium chloride, drawing parallels to making a pitcher of the drink mix.

7. Pour some of the 0.1M NaCl into different-sized beakers. Ask the students to

compare the concentration of solution in each of the containers.

8. To recap, bring out a 1 liter beaker and several stuffed moles. Adding one

mole gives a 1 Molar solution. Stuffing in a second mole gives a 2 Molar

solution. With a flourish, separate a third mole at the velcro strip

joining the front and back ends and make a 2.5 Molar solution.

9. The lesson can be extended by placing stuffed moles in other sizes of

beakers and calculating the molarity of the resulting "solutions."

**References**:

^{*}Weird Science #5 (for mole pattern). Make one special mole by constructing

the front and back halves separately and then joining them with a velcro strip.

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