Dorothy Manning, Edgemont Elementary, Idaho Falls, ID THE MOTION OF MOLECULES IN WATER Appropriate for grades 4-7. OVERVIEW: The concepts involved with atomic theory are difficult for teachers to demonstrate because the particles involved are too small to actually see and manipulate. Whenever possible it is helpful to allow students to observe actual concepts and then either develop their own theories about what was seen, or reconcile what they have seen with what they have been taught happens. PURPOSE: The purpose of this activity is to assist students to visualize and better understand the concept of the constant motion of molecules. OBJECTIVES: Students will be able to: 1. Observe the motion of water molecules using food coloring. 2. Compare dispersal time in hot, cold and room temperature water. 3. Record observation data on record sheets. ACTIVITIES: Fill the beaker or jar 3/4 full of water. The students should be able to see the water level and that it is clear. Place the beaker where it can be seen by the students but will not be disturbed with any type of motion. Carefully place a few drops of food coloring on the surface of the water. Do not agitate or stir the color into the water. Allow the beaker or jar to sit and observe it periodically during the lesson. The color will disburse throughout the water. Depth of color will depend upon time allowed and how much food color was used. To determine whether the temperature of the water has an effect, do the activity again using hot water and using the coldest water possible to obtain without freezing the water. Record the time it takes for the color to disburse throughout the water. RESOURCES/MATERIALS NEEDED: A clear glass jar or beaker (large enough to be easily seen by students), Water, Food coloring (a dark color such as green or blue is more easily seen). Because of the time involved in allowing the food color to mix, student need to either be working on a related lesson which can be stopped periodically at the instructor's direction to refer to the activity, or students should be recording the activity on experiment record sheets. TYING IT ALL TOGETHER: 1. Have the students illustrate the activity using a series of pictures. Students could illustrate the activity from the perspective of an individual molecule, or as a record of what the student observed happening at certain time intervals. 2. Students could write a summary on the activity describing what they observed happening. The summary could be factual and scientific, or could be in short story form as told by a molecule of water or a molecule of food coloring. bit intimidated by the stars if they have no prior experience.
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