This chemical reaction is very interesting. If one dissolves copper sulfate in water and places a bare iron nail in that, the iron replaces the copper in the sulfate salt and makes very fascinating hairy growths on the nail. I did this reaction with some of my copper sulfate, commonly available as root killer for sewers, and it turned out quite well. I like how the solution turns a greenish color and the nail becomes a furry, coppery tree trunk. Check out my YouTube time lapse I made of the reaction!
After finding some free time recently, I decided to come back to my Raspberry Pi, so I whipped up a quick website. I currently have the Apache server with PHP running on my Model B Pi. I like webpages that have a link to something in the real world, so I made a page that shows the temperature of the Raspberry Pi CPU. You can view the HTML, CSS, and PHP code right here. The HTML code is pretty basic; just the regular tags for the simplest of webpages. One interesting tag, though, is the <meta> tag, which tells the viewer's browser to automagically refresh the page every 10 seconds to display the most up-to-date CPU temperature information. All that the CSS does is give the PHP-generated text some snazz, centering it, making it larger, and coloring it. The CSS also gives the page a nice repeating background image (located on the Raspberry Pi in the same directory as the webpage), available here. The PHP code is the really interesting part. It may be intimidating; I condensed it so save space. However, it really isn't all that complicated. The first line executes the command "cat /sys/class/thermal/thermal_zone0/temp" and assigns its output to the variable "$outarray". The command just reads the Raspberry Pi CPU temperature file, located at "/sys/class/thermal/thermal_zone0/temp". This file contains the Raspberry Pi's CPU temperature in millidegrees Celsius. "$outarray" is apparently an array, so the next line treats it as such, reading the zeroeth element, dividing that by 1,000 to get degrees Celsius, and then multiplying it by 9/5 and adding 32 to get Fahrenheit. It then assigns this temperature to the variable "$temperature". The last line of the PHP code echos (prints on the webpage) this result, using the "round()" command to get rid of unnecessary decimal places. Directly after this block of PHP code is "°F", which codes for the degrees symbol and then an "F" to represent Fahrenheit. Thus, the end result might be "101.3°F". I am quite pleased with the results- I have a nicely-formatted auto-updating webpage that shows my Raspberry Pi's CPU temperature in Fahrenheit. Have a blast, and don't bake your Raspberry Pi!
I had some 60/40 tin/lead solder that I decided to experiment on, so I first melted it into a nice blob. Pretty, hefty, and solid, but not super-exciting. So, I decided to try pouring the molten alloy into water, to see what would happen and to hopefully make nice granular pellets for science experiments. For those of you who don't know, "mossy" metal is what you get when you pour metal into water, so it makes really shiny oddly-shaped blobs. I poured a coffee bean can full of water and then melted my solder in a tin can with a propane torch. It melts quite easily. Then, I poured it into the water, trying to pour slowly and make the solder fall in little blobs. It worked pretty well:
As you can see, I got some really shiny mossy solder. I also got three weird "fuzzy" spheres of alloy, which brings me to an extremely important point: this is dangerous. I hypothesize that the fuzzy spheres are caused by a fairly large amount of molten (read: hot) tin/lead alloy exploding itself inside out while under water, kind of like popcorn. They are really quite thoroughly exploded. If this molten tin/lead mixture exploded onto your skin, eyes, or other important body parts, I can predict that you would not be happy. I was wearing splash goggles and full winter clothing, but leather gloves and a face shield would have been even better. Have fun, and be safe!