I dusted off an old slide show on nuclear physics for class today. I explained how atoms of the same element and hence the same number of protons can have different numbers of neutrons and hence a different mass. But since the number of protons is the same, they are still the same element. These are called isotopes and some are more stable than others. We also talked about half-lifes, carbon dating and alpha/beta and gamma decay, nuclear power plants and atomic bombs.
Our lab today was about spectroscopy and looking at the emission spectra from different sources. I have a spectroscopic analysis kit from home science tools that comes with 4 different salts and one spectrum viewer. I actually have two of these viewers, bought an extra when I bought this kit for about $10. You soak the wooden sticks in a cup of water for 15 minutes so they don’t burn when you stick them in the flame. Once your sticks are done soaking you stick the wet end in one of the chemicals to get a few clumps of salt on your stick. Then hold the salted end of the stick in a candle flame and observe the color of the flame with your eyes and then through the spectrum viewer you will observe lines of color – mostly orange/yellow and some red. We did this lab but I also had the kids make their own spectrum viewer to take home. I found this mini-foldable spectrometer at publiclab.org. All you need is some dark colored cardstock and a dvd-r disk to cut up for the diffraction grating. They have detailed instructions and photos on the website for putting this together. Shown below is a spectrum from a compact fluorescent light bulb. You get very distinct lines emitted from the gases inside the bulb. LED bulbs on the other hand, or sun light, give you a nice broad spectrum. A couple of the students managed to get pictures of the colored flames, 1 or 2 bands of color, but they were very dim. There is a website, SpectralWorkBench.org where you can upload your spectrum and calibrate it but I haven’t gotten to far in that process.