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The Science of Soda Pop
In my school we have just begun to restrict student access to pop machines throughout the day. The students were a bit unhappy about this change and that provides a teachable moment where we can dig into what is in soda and how that might impact their health.
If you live in one part of the country it is called pop and another part it is known as soda. It all has carbon dioxide and that is a pretty good place to begin. With a balance and a few cans or bottles of soda you can remove the CO2 from the beverage by simply letting the can stand open or even with a little agitation. The shaking works better with bottles. This experiment is detailed at this site:
There are good inquiry activities that can come from letting the students generate questions about soda. One that usually comes up is, “how much sugar is there in soda”? You can place the soda in a beaker or pan and mass the liquid. Then evaporating the water slowly and massing the container after evaporation you can see what percentage of the mass of a soda sample is not water. Most, of that left over mass is sugar (unless you are using diet pop). My students tested 7 different kinds of sodas. The amount of sugar actually astounded them.
Lots of students will wonder where pops came from. Who invented them? Most web sites link them to mineral waters. There is a good history at the About.com site.
No investigation of soda pop would be complete without allowing the students to try to make some sort of pop. Most of the web instructions center on ginger ale and root beer. The key to making carbon dioxide is to let amazing yeast do its biological best. There is some great biology in how that works. That is a topic for another blog post. Try these sites for easy to follow instructions.
My students also tried making soda using simple club soda or unflavored sparking water with some interesting fruit juices. The science of flavorings is an interesting exploration in high school chemistry classes. From this flavoring activity the students gained understanding about how much sugar was needed to make the drink palatable to most. We did try artificial sweeteners. This portion of the unit may give you a good time to talk about the biology of the sense of taste and how much sweeter than sugar certain sweeteners appear to the taste receptors. Wikipedia has a good article on the most important 6 of these sugar substitutes.
No unit on soda would be complete without an investigation using pop and Mentos. If you have never done this you need a packet of Mentos mints, a 2 liter bottle of some cola and clothes that you do not mind getting covered with soda. This is an outside only activity as placing the Mentos in the bottle of cola will cause the cola to bubble with enough action to spew out of the bottle like a cola volcano. There is a good video on this activity at the Steve Spangler site.
In my state standards the students at all levels are required to become familiar with the skills of inquiry:
- Learner engages in scientifically oriented questions
- Learner gives priority to evidence in responding to questions
- Learner formulate explanations from evidence
- Learner connects explanations to scientific knowledge
- Learner communicates and justifies explanations
Allowing students to generate questions about pop and explore them to seek evidence is inquiry in action.