Saturday, September 26, 2015

Using Body Movements to Teach Molecule Behavior in Solids, Liquids, and Gases

Students modeling the molecule behavior of solids
Students modeling the molecule behavior of solids

Learning is done best by doing.  This can be difficult in science when you are teaching a concept like molecule behavior to upper elementary students. I like to use body modeling for tough concepts like this whenever possible. The students are actively engaged and it allows them to 'SEE" the concept in a way they may otherwise be unable to. This particular body modeling lesson is a personal favorite of mine and I'm really excited to be sharing it.

Before you begin your lesson, all desks and chairs need to be stacked against the wall. The students need lots of unobstructed floor space for this activity.

Modeling Solids

I begin the lesson by arranging the students into an array that resembles a square or rectangle and tell them to stand with their hands by their sides. To activate prior knowledge, I ask questions about what they already know about solids.
  1. What happens to the shape of a solid if I move it from one container to another?
  2. What happens to the volume of a solid if I move it from one container to another?
  3. Are the molecules touching? 
  4. How are they touching? 
  5. Do they change places with other molecules? 
  6. Are they moving at all?
  7. How can we arrange ourselves so that we would look like the molecules in a solid?

The last question may be more difficult for some classes than others. If they have a lot of prior knowledge, then they will probably have lots of suggestions. I take their suggestions and guide them until we agree on an arrangement that works. It almost always ends up looking like the photo above.

  • The molecules in solids are organized. The students usually ask if that is why I had them stand in an array. If they don't, then I will ask if anyone can think of why I would have them stand that way.
  • The molecules in solids touch. The students connect together by placing hands on shoulders.
  • The molecules in solids vibrate in place. This looks different for each class. Some classes simply rotate their hips like they are using a mini hula hoop. Other classes shake their whole body like they are being electrocuted. That one is always fun.

Changing from a Solid to a Liquid

After having the students model molecules in a solid, I prompt them to give some examples of solids. When someone gives the example of ice, I ask how we could turn ice into water. I lead the conversation if necessary but it usually doesn't take long before someone says that we have to add heat.

Modeling Liquids

Using the same questions that are listed above, I ask students about molecule movement of liquids. The students make suggestions about how they should arrange their bodies and how they should move to model how molecules behave in liquids.

  • The molecules in liquids are unorganized. Students do not have to worry about staying in an array.
  • The molecules in liquids are touching. Students should use one hand to touch the shoulders of classmates as they move.
  • The molecules in liquids change places with other molecules. Students slowly move around while touching the shoulders of various students as they go. This is preceded by a very short talk about paying attention to how you move your body and respecting the personal space of others.

Changing from a Liquid to a Gas

After the students have modeled the movement of liquid molecules, we talk about what would need to happen in order for them to turn into a gas. Given that we just talked about adding heat to a solid to turn into a liquid, it doesn't take long before someone mentions adding heat. 

This is a great opportunity to see if they remember that the boiling point of water is 100 degrees Celsius. 

Modeling Gases

By this point, the students are really leading the lesson. They have enough prior knowledge that, by asking the questions listed in the Modeling Solids section, they can describe how they want to move their bodies with very little input from me. I make sure to list safety expectations such as walking fast instead of running or not bumping into walls/furniture. 

  • The molecules in gases are unorganized. The students do not have to worry about keeping to a certain pattern.
  • The molecules in gases do not touch and they will occupy as much space as you give them. The students move quickly around the room without touching each other. If they do not do it on their own, I will remind the students to spread out and use all of the floor space (even the corners of the room) to model the fact that gases take the volume of their container.

Changing back to a Solid

By now the students are comfortable with modeling the three states of matter and understand that you have to add heat to change from a solid to a liquid to a gas. I ask the students to line back up into their original arrays and let them run through the model so they can see the state of matter changes in action. I tell them to wait for me to call out "ADD HEAT" before they change from one state to another.

After they have run through the entire model, I bring up changing back to a solid. I allow a little think time before I start to take responses.

I'm looking for someone to suggest removing heat.  This may take a little coaxing from me because the students usually want to say to add cold since earlier we said to add heat.

This is where we talk about the fact that heat is really just a measurement of energy. The more energy the molecules have, the more heat they have. Therefore, to move from a gas back to a liquid you would have to remove heat. I also take the opportunity to question them on the freezing point of water.

The students then run through the entire process while I call out "ADD HEAT" and then "REMOVE HEAT". As an added fun bonus, I will record their final body modeling and let the students watch themselves in action. This is both super fun for them and gives me the opportunity to ask deeper questions if needed. I always have the students talk about the flaws of our model.

Closing the Lesson

Although this lesson has a lot going on, I can typically get through it in one 45 minutes class with time left for a quick exit ticket. Here are a few of the prompts that I've used in the past.

  1. Describe and illustrate the movement of molecules in a liquid.
  2. a solid.
  3. a gas.
  4. Why do liquids take the shape of their containers?
  5. Why do gases take the volume of their containers?

I hope that you and your students enjoy this modeling lesson as much as my students do. If you have any body modeling lessons you'd like to share, I'd love to hear them!!

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