Photosynthesis

I've been subbing in the public schools the last couple months (quite an experience after 10 years of homeschooling, but that's another story). Last week I had to go over plants with a class of third graders and then give them a test.

In the review materials, their teacher had given them the following formula:

CO2 + sunshine + water = food

This really made me nuts. When my kids were a little younger, I made it a point to find out just how plants turned sunshine into food. It took some doing, but I finally found a DK book that spelled out the relevant chemical formula. Which is this:

6CO₂ + 12H₂O + sunlight ---> 6O ₂ + C₆ H₁₂O ₆ + 6H₂ O
or...
carbon dioxide + water + sunlight --->
oxygen + carbohydrate + water

Now, she's already given them a chemical name (CO2 -- I asked and one child identified it as carbon dioxide). She could very easily have then given them H2O, water, and then done the math. The carbohydrate, glucose, is a form of sugar, which they would have readily understood -- especially here in upstate NY, where maple sugaring is common!

Actually, I was surprised to see "sunlight" in the actual formula; it provides the energy via chlorophyll, a green pigment that absorbs energy from sunlight. But most amazing of all --

THERE WAS NO MENTION OF CHLOROPHYLL!

(And photosynthesis was hand-written in on the test as an afterthought; I had to help the students out by letting them know that photo means light and synthesis is making something.)

Just to understand, as with most public-school science in my experience, the information the kids had to know was basically all vocabulary. For instance, they had to correctly label the cotyledon of a seed. Now, I doubt there are many adults who can identify cotyledon but not chlorophyll. Really.

Anyway, here, for the record, is my third-grader-friendly, chemistry-literate explanation of how plants make food. I am looking forward to exploring biology again (my plan for next year) in light of my ever-growing comfort with chemistry.

Radioactive Elements

I became interested in radioactive elements after my brush with thyroid medicine, and I started looking on eBay for a cheap Geiger counter. (My dad, who worked with X-ray machines, brought one home and demonstrated it for us when I was a kid -- another example of how early impressions about science can stick with you.) Before I could finish my research, a friend bought one for us. Turns out, what we actually have is a radiation detector intended for survivors of nuclear war. As one site I read said, if this thing shows a reading, evacuate!

So when I wanted to look at some common household radioactive items, we still didn't have anything to measure them with.

(This didn't work.)

So we found some nice videos on YouTube from people who did have real Geiger counters.

Among the radioactive items people collect or have about are:

smoke detectors (Americium)
salt substitute (potassium isotope)
Fiestaware dishes (the famous orange-y red made with uranium)
gas lantern mantles (a favorite of The Radioactive Boyscout)
old luminous watches (radium)

But here in Saratoga Springs, NY, we have one source of radioactivity that is less common: mineral water.

Back in the 1800s, Saratoga was known for its horse racing, its casinos, and its spas. Its many springs, the result of a geological fault which runs right through the center of the city (it's a low point known until recently as "The Gut", but now the source of trendy new restaurants). Apparently radioactivity is one requirement for "really good" mineral water.

The radioactivity comes from radon gas -- the same stuff that accumulates in basements, a by-product of the decay of uranium -- dissolving in the water underground. Once in the air, the radioactivity dissipates quickly, with a half-life of about four days.

Nevertheless, for the sake of science, we took a walk over to the Saratoga Spa State Park and collected a few bottles from the Polaris spring, one that is known to be radioactive. We also took a sip (it's carbonated but pretty sulfurous, so you wouldn't want to drink it regularly anyhow). So far, no one is glowing in the dark.

The radiation detector wasn't a total loss: it came with a really enlightening manual about radiation safety, for perusal in your fallout shelter. This article from the World Nuclear Association is also basic enough for kids. You'll also find all kinds of fascinating information about radiation at Theodore Gray's Periodic Table.

I'm still planning to get a working Geiger Counter, and maybe a few odds and ends from United Nuclear.

A word from our sponsor

A new chemistry post should be up this weekend, but in the meantime I'd just like to mention that I've just published my first book AROUND THE WORLD CRAFTS: Great Activities for Kids who Like History, Math, Art, Science and More!

The book is a collection of my Hands-on Learning columns from Home Education Magazine.

Enjoy!