Ending with Nuclear Chemistry
My half life lab activity is the last one of the school year. There are a few reasons why I teach nuclear chemistry at the end of the year instead of during my atomic unit. First off, many of my students will think that EVERYTHING has to do with the nucleus for the rest of the year. I’m not sure why that is, but it has happened to me for all the years nuclear was taught during atomic.
Next, nuclear chemistry usually aligns with the time that my students are learning World War II. It’s a good time to attempt “interdisciplinary learning.” The kids kind of have a historical background and then I can go and teach them the scientific “how.” And lastly, nuclear chemistry is really fun. The half life lab activity I do with them is a lot of fun. And nuclear always gets the gears turning and kids ask A LOT of great questions that we ACTUALLY have time to address.
The Final Lab of the School Year
My final lab of the school year is the “Half Life of a Skittle” lab activity. Each student is given a bag of skittles for this half life lab activity. Each skittle represents an atom of a radioactive element. If you’re not fond of giving the kids sugar, you can swap these out for coins, or dice. The idea is that the kids are supposed to shake the sample for some amount of time. This time is the half life.
Choosing a Half Life
I like to make my students shake their samples for 45 seconds. I don’t like to have the half life be one minute, because then the number of half lives is equal to the amount of time that has passed. This can throw kids off and give them the wrong idea. I also like to use a shorter amount of time because the S on the skittle very easily wears off during shaking, and we don’t want that to happen. We need the S to determine what is stable, and what is still radioactive. Forty-five is a nice number for math but ugly enough for separating the concept of half life from the actual passage of time, if that makes sense.
Stable or Radioactive?
Okay, so after 45 seconds of shaking the skittles, they dump out the skittles onto a paper towel and separate them into two groups. Stable isotopes and unstable isotopes. All of the skittles that land S up are considered stable isotopes. Considering that skittles are (kind of) two sided, the S up population should be about 50%. If you swapped out skittles for coins, choose one face to be stable and the other unstable. For dice, you must choose even or odd numbers for this to work.
The students then scoop up the “radioactive” skittles and continue shaking for another half life. Eventually they will have collected enough data that they get a nice decay curve. I have my students graph this information and really see what it’s all about.
Nuclear Decay Graphs
This year, I’ve moved away from graphing by hand and I’ve had the kids using Google Sheets instead. The graphs come out way better and more accurate. I also like that the kids are implementing some technology in the lesson. Last year during hybrid teaching, I did a digital version of the half life lab activity. It was pretty lack luster, but I did the lab myself and took pictures of the skittles sample. Then I put those in a slide show, one slide per trial. The kids then counted from the photo and collected the data. Certainly better conducted in person, for sure! And more delicious, because I let them eat the skittles at the end, of course!
Writing Lab Reports
I’m a HUGE fan of having my students write full on lab reports (more than just some post lab questions.) You can read more about my strategies here, and you can snag my lab report outline right here!
