on the topic of Science Teaching
Yes…molecules do move. Not just those in a liquid, but in solids and gases, as well. This is a concept that many middle school students have difficulty understanding. Most of my students readily accept that fact that liquids move because they have had experience observing liquid molecules in motion. Each time they take a bath or mix Kool-Aid in water, they are able to see the motion of a liquid. However, it is harder for my students to believe that solids and gases are also in constant motion because that motion is not visible.
The motion of liquids, solids and gases is explored in the remainder of Chapter 1 of the MSC, as well as the effect that thermal energy has on each state.
In the first lesson, Molecules in Motion, my students engaged in a simple, yet effective activity that illustrated not only the movement of water molecules, but how temperature affects the rate of movement. By adding food coloring to cups of hot and cold water, my students were able to observe the difference in motion of hot and cold water molecules.
In order to get my students to understand what was happening at the molecular level, I found that the MSC included an excellent multimedia resource. In this interactive application, you are able to manipulate the temperature of a substance and observe how the motion and position of the molecules is affected.
In the previous lesson, I had my students complete the activity sheet on their own. After looking over the responses though, I found that many of my students weren’t responding appropriately, particularly when the question asked them to extend their thinking. I felt that it would be more helpful to discuss the questions with the class and guide them through the though process. Due to this, I decided that I would work with the students to complete subsequent activity sheets.
Solids are explored in the lesson Moving Molecules in a Solid. The lesson involves using a ball and ring device to illustrate how solids expand when heated. Although I do have a ball and ring in my classroom, I do not have access to a Bunsen burner, which is necessary to heat the ball. Initially, I was disappointed that I wouldn’t be able to share this demonstration with my students, but I quickly realized that the MSC provides videos of demonstrations that are not able to be conducted in the classroom.
Finally, gases are explored in Air, It’s Really There. This lesson is similar in structure to those on liquids and solids. Animations of the movement of molecules and videos of demonstrations are provided, but I must say that my students were most impressed with the exploration portion of this lesson.
In the exploration, students were each given a plastic water bottle, dish detergent, and cups of hot and cold water. The students dipped the opening of the water bottle into the dish detergent until there was a soap film covering the opening. Carefully, students then dipped the bottom of their water bottle into the cup of hot water. As they did so, a bubble began to form and expand. My students were even more amazed when I had them transfer their bottle to the cup of cold water and their bubble began to invert.
My students were quickly able to describe what was happening on the molecular level that caused the soap bubble to behave differently when dipped in hot and cold water. Never before, had my students been able to grasp a concept so quickly and easily.