Diffusion Of Molecules

Submitted by:Margaret Sorensen, Holy Rosary Elementary School; Idaho Falls, Idaho
Endorsed by: 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.
Date: May 1994

Grade Level: Third/Fourth Grade Chemistry

OVERVIEW/PURPOSE:
l.  Molecules in a liquid move.
2.  Molecules do not more in any specific direction in a
    liquid.
3.  A solution is a liquid mixture of two or more
    substances in which the substances are completely
    mixed.
4.  Heat will increase and cold will decrease the speed
    of molecular movement in water.
5.  Stirring will increase the speed of molecular
    movement and the speed with which substances will
    dissolve.
6.  Rubbing alcohol and soap makes molecules move faster
    in water.

OBJECTIVES:
l.  To understand molecular movement
2.  To develop skills in performing a chemistry
    investigation.
3.  To develop skills in making hypotheses.
4.  To develop observational skills.
5.  To develop creativity and imagination in modifying
    science investigation.

RESOURCES/MATERIALS:
food coloring, watch, water, eyedroppers, warm water,
rubbing alcohol, dish soap, ice cubes, plastic cups, small
plastic bags

    VOCABULARY:  dissolve, diffusion, molecules

ACTIVITIES AND PROCEDURES:
l.   This activity can be done with an entire class, as a
     learning center group activity or as an individual
     project.  Do not go over the concepts at this point.
     This is a discovery activity in which the children
     figure out the concepts from the results of the
     investigation.
2.   Distribute the materials to the students.  Each will
     need a clear plastic cup of water and an eyedropper
     holding some food coloring for the part of the
     experiment.  While most of the students are working on
     this activity, have your student helpers pass out small
     plastic cups of warm or hot water.  The alcohol, the
     dish soap and the food coloring may be distributed in
     containers to be shared.  Any colors of food coloring
     will work, but red and blue are the easiest colors to
     see as they dissolve.
3.   Encourage your fast-finishing students to do each
     investigation a second time, comparing the speeds and
     keeping a record of the results.  Children should know
     that experiments are checked many times by real
     scientists.
4.   Place a drop of food coloring in a cup of water.  How
     many seconds did it take to completely dissolve in the
     water?
5.   Place one or two ice cubes in the cup of water.  Place
     a drop of food coloring on an ice cube.  What happened?
6.   Place a drop of food coloring in the cold water.  How
     many second did it take for the food coloring to
     completely dissolve in the cold water.
7.   Place a drop of food coloring in a cup of water.  Add a
     few drops of alcohol.  How did the alcohol affect the
     solution?
8.   Add a drop of food coloring to a cup of warm water.
     How many seconds did it take for the coloring to
     dissolve completely in the warm water.
9.   Add another drop of food coloring to the water.  Then
     add a few drops of dish soap to the water.  What
     happened?


TYING IT ALL TOGETHER:
This activity integrates well with art.  Your students can
use markers, colored pencils, crayons or watercolors to draw
their own versions of the designs produces in the cups by
the dissolving food coloring.  This makes a very colorful
bulletin board display, especially if the construction paper
the children are is drawing on is cut into the shape of
large cups.