Date: May 1994

Grade Level(s): 9, 10, 11, 12

Subject(s):

• Science/Chemistry

It is difficult for students to understand the concept of solutions and concentrations. A visual model is very helpful as an aid to learning.

PURPOSE:

The purpose of this project is to give students a hands on model to work with which will demonstrate the manner in which solutions are formed.

OBJECTIVES: Students will be able to:

1. Discuss pure solutions.
2. Discuss dilute solutions.
3. Discuss concentrated solutions.
4. Discuss the volumetric changes which occur.
5. Apply use of the model to future learning.

RESOURCES/MATERIALS: Materials needed are listed above in the activities section.

ACTIVITIES AND PROCEDURES:

1. Each lab table is provided with four 300 ml. beakers. Each beaker contains one size and one color of glass or plastic spheres. The spheres range in size from l mm. to 8 mm. in uniform increments, each size sphere having its own color.
2. The students are led to understand that the beakers represent single molecules of pure substances.
3. The students first record the volumes of each of the beakers and enter this information into their data tables.
4. The students are then told to pour the beaker of smallest spheres into the beaker of largest spheres and mix well with a glass stirring rod. The new combined volume is then recorded in the data table. (The students note that the smaller spheres tend to fill in the spaces between the larger spheres, thus demonstrating the addition of a solid to a liquid forming a solution.)
5. Students are encouraged to make many combinations of different sizes and colors of spheres and to record the volumetric changes.

TYING IT ALL TOGETHER:

In subsequent work with solutions and concentrations, students are encouraged to refer back to the models as an aid to understanding. A set or two of these beakers are left on display for student use to encourage further exploration.

May 1994

These lesson plans are the result of the work of the teachers who have attended the Columbia Education Center's Summer Workshop. CEC is a consortium of teacher from 14 western states dedicated to improving the quality of education in the rural, western, United States, and particularly the quality of math and science Education. CEC uses Big Sky Telegraph as the hub of their telecommunications network that allows the participating teachers to stay in contact with their trainers and peers that they have met at the Workshops.