Don't Know Much About the Science Books; Don't Know Much About the French I Took...

In a few short weeks, my classmates and I will be going into the classroom to teach a science unit to 3rd graders. We've been assigned a "changes" unit where we will be working with the kids to help them understand the properties of solids, liquids and gases and how these properties can change if they are combined with other matter.

Our lesson will center around dropping tablets of Alka-Seltzer into water and observing what happens. Anyone remember the old "plop, plop, fizz, fizz" slogan? Funny how times "change."


In order to lead the lessons, we're going to have to become the experts in the room on all things that matter...when it comes to matter. This is the first of many lesson plans we'll be teaching, so we need to develop tools and practices in order to properly prepare for each lesson. Here's what I plan to do.


First I thought about the lesson and tried to put myself into the shoes of the learners. If I were seeing this for the first time, as many of them will, what would I want to know? I would definitely want to know what happaned to that tablet! I'm quite certain I would think it disappeared right in front of my eyes. In fact, even before reading the lesson plan, I probably would have said it dissolved into the water, and that's not exactly true either. The real story is that it turned into a gas. But how do I explain that to a group of 3rd graders?

Um....well, how about Google?

1) How does Alka Selzter work?

After poking around on a few sites, I discover that the "fizz" is caused by the release of carbon dioxide when combined with water. Steve Spangler even teaches us how to make an Alka Seltzer rocket! Cool! Maybe for Lesson Plan 3?? *grin*

2) OK, so what is carbon dioxide? Isn't that what we breath?

Cardon dioxside: a colourless, odorless, tasteless gas that is produced when animals exhale (I was right!) and when fuels burn and is used by plans to make food. Cardon dioxide is a "Greenhouse Gas".

Well, that's a good definition, but really not all that useful for my purposes. Let me ask this a little differently.

3) What hapens when I put Alka Seltzer in water?

This yielded differen results, including a link to "the Office of Science, U.S. Department of Energy". Who knew?

A much more palatable answer:

One of the main ingredients of Alka-Seltzer is baking powder. Baking powder is a
combination of some acid (such as citric acid or tartaric acid) and sodium bicarbonate. When the tablet dissolves the components of baking powder (the acid and the base)react with each other and produce a gas (carbon dioxide).

OK, I see, so adding water to the solid, allows the solid to dissolve and react with the water, releasing the gas (a chemical reaction!). The gas makes the bubbles. The bubbles are the gas. So, in a chemical reaction, when two substances react together, they can form new chemicals or products.

I also checked out some of my classmates blogs for additional inspiration. Becky (along with many others) linked to our friends, Moby and Tim at Brainpop, and by watching this video, I learned a new term called "sublimation". This is when a solid changes directly to a gaseous state without ever becoming liquid. This term may be a bit advanced for the 3rd graders, but we can introduce the concept and make sure that what they take away from the experiment is that:

• all matter has 3 "states" (solid, liquid and gas)
• those states change due to changes in temperature and pressure
• it's a purely physical change becuase the chemical properties stay the same

Cool. Plop, plop, fizz, fizz, oh what a relief it is.