Building Student Vocabulary in a High School Science Class

Boys Republic High School science.

The place, Boys Republic High School, the class combined Earth Science and Biology.

“Hey Mr. Burns I remember doing this in fifth grade. You put water in a bottle and squeeze it to get a cloud.”
“See I told you this was too easy. He did it in the fifth grade. I need to get my credits. I need to get into the book. Not mess around with this stuff.”

So began my lesson third period, intended to help students define evaporation and condensation, see a demonstration of cloud formation in a two-liter plastic bottle and finally have some joy and laughter while making soap bubbles with dry-ice (frozen carbon dioxide).

My response to my resistant student who thought this was too easy:

“Sean, if I was at the university teaching a college class I would bring in two-liter bottles and start the lesson the same way. Give it a chance we are going to have some fun and make some bubbles later on.”

To make a cloud appear in a two-liter plastic bottle you need to add some warm water and a match or small piece of paper to add a bit of smoke. Then cap the two-liter bottle tightly. You can demonstrate for students that a cloud does not appear in a bottle that contains only warm water. The bit of smoke allows a place for water molecules to condense. When the bottle is squeezed it represents warm air (Figure A), when you release the bottle the air expands, as the air expands it cools and water vapor condenses on the smoke particles. I use the diagram depicted above to relate the demonstration to actual cloud formation in illustrated form.

Student steps for making a cloud in a bottle.

Wanting my students to gain an appreciation for how we are surrounded by water vapor. I place rubbing alcohol on the back of their hand and ask them to blow so they can feel the temperature change. You can see evidence in the student work below that they can also relate this demonstration to an explanation of how sweating helps the human body to cool down. With the two demonstrations; cloud in the bottle and rubbing alcohol on the back of their hand, we have examples to refer to as we define the terms evaporation and condensation, using a Frayer Model.

Before filling in the sheet for evaporation, I project for the students a definition of evaporation.

fotor® created collage

I believe one of the strengths of the Frayer Model as a graphic organizer is to have students define terms in their own words. We also fill in characteristics, examples, and non-examples. The cloud in the bottle activity can be referred to in discussion for both evaporation and condensation. Adding warm water to the bottle saturates the air in the bottle with water vapor (example of evaporation; change of state from liquid to gas). By squeezing the bottle and letting go the air expands and cools allowing the water vapor to condense on the smoke particles (example of condensation; change of state from gas to liquid).

Student example Frayer Model for evaporation.

You can see the student has placed sweating in the non-example area and may have ended up developing a misconception rather than a deeper understanding of evaporation and condensation. Sweating is a real life example of evaporation and cloud formation is an example of condensation.

The remainder of the period we put to use our understanding of evaporation and condensation by making bubbles. A plastic tube is connected to the lid of a plastic tub filled with water and a few pieces of dry ice. The open end of the plastic tube is dipped in a soap solution (Figures B and C). Since carbon dioxide gas is denser than the surrounding air the bubbles fall to the table. As they pop in a student’s hand they notice a change in temperature. After all the students have a chance to feel the temperature change and pop a few bubbles I ask them:

“If carbon dioxide is a gas, why is it that we can see it? Why does it seem to also disappear?”
I have to be patient with my questioning of students for them to realize and then verbalize that the “cloud” of carbon dioxide is actually water vapor in the air being cooled by the sublimating solid carbon dioxide (dry ice) as it changes from a solid directly to a gas.

Another fun thing to do is to place a penny on a piece of dry ice to make snow. You can also make a whistling sound by pressing the penny down on the surface of the dry ice. The great discovery of the day (sorry no picture to capture the moment) was when we poured soap directly into the container and reached into to grab a piece of dry ice, place it on the table with a bubble forming over the top. As the small piece of dry ice slid over to touch the side of the bubble a small portion of the bubble froze and at least I was AMAZED.

In the future I want to have my students make digital Frayer Models of words/concepts they encounter. Concepts they deem important and create collages using fotor and annotate their collages using thinglink.

Is accurate to the best of my memory and

this is what I wish had happened and I now have some purposeful questioning to do of students the next time I try this lesson.
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