Peering into the microscopic world

Jr. scientist A just got a microscope (thanks Arthi and Glenn!), so we've been exploring the microscopic world. He instantly noticed that there was something very telescope-y about this new device ("it has a focus knob!"). As with the telescope, I wasn't sure how much he would be able to see through the lens, so we played the "what do you see" game. We looked at some string (top right photo), which he described as "branches" - a pretty good description. We also looked at colored sugar (bottom right photo), paper, grass, salt, sandpaper, and a few other things. Jr. scientist A had a lot of fun, but this was another one of those experiments where he had to compete with the adults for a turn!

Stalagmites and stalactites, take 3

Never willing to admit defeat, we've made another try at making stalagmites and stalactites. We noticed that the area around our crystal experiments was covered with crystals. It seems that the salt water evaporated in the hot sun, but was too heavy to stay in the air and condensed out. We decided to take advantage of this to try to grow stalactites. We put a mesh (a cut-out from a screen door) on top of the jar for our latest experiment, hoping it would catch the escaping evaporated salt water. We poured our crystal making materials into the jar while it was covered by the screen so some of the liquid would stay on the screen and start a layer of crystals for the rest to hang on to. We weren't able to grow stalactites with this technique, but we got an unexpected but happy result. The evaporated salt water seemed to get trapped inside the jar so we ended up with one big thick crystal that covered the bottom of the jar. Pretty cool. I want to try this in a disposable cup next time so we can easily get the crystal out to play with. It looks like we'll finally have crystals that aren't to delicate to handle.

Ice melting experiment

We had previously used salt to briefly drop the melting point of ice. This time we tried it on a larger scale. We made two ice cubes. The first one (red in the video) was made using water that had Epsom salt dissolved in it. The second one (green in the video) was made using plain water. This wasn't exactly the cleanest experiment - the plain water cube ended up noticeably bigger and was frozen for a shorter period since we already had salt ice cubes sitting around - part of a long-term experiment I'll write about when it's finished. But I expected the effect to be large enough that the general results would be unaffected. As shown in the video, the salt ice cube did melt much faster (about half an hour compared to 1.5 hours for the albeit larger plain water ice cube). You can see from the pool around the edge of the plate how much quicker the salt ice cube was melting. The two ice cubes also melted in very different ways. The plain water cube primarily just got smaller. It still had the typical smooth edges of an ice cube. The salt ice cube started looking very rough and "eaten away" even though it started out smooth. The one oddity was that the plain water ice cube started melting much quicker. We may need to do a more controlled experiment. Although Jr. scientist A enjoyed watching the ice cubes melt, I was surprised that he showed little interest in the sped up video, which I thought would be easier for him to grasp.

Crystal growing mediums

Since our previous attempts at growing stalactites have yet to yield anything remotely resembling a stalactite, we decided to take a step back and do some pilot experiments. There seems to be a few problems that potentially need to be addressed. 1) How do you get a nice slow drip for the salt water so that the crystals can grow over time? 2) What type of materials will the stalactites grow best on? 3) How do you refill your salt water solution without dissolving the already formed (water soluble) crystals (i.e., whatever makes the slow drip has to either never release the solution faster than a drip or be detachable)? I'm sure there's a few more we'll run into.

We've previously made some good progress on the first problem. We decided to attack the second problem by trying to grow crystals on different materials. We made our crystal solution, dissolving as much salt as possible in super heated water. This time we used table salt - nice and safe to handle and eat (good for a toddler hands-on experiment, that is, once the water has cooled). We poured the crystal solution over cardboard, paper, wood (a popsicle stick), and wool yarn. We set the materials in a window for a couple days and then checked on our results. The crystals grew everywhere (including on the plastic container the materials were in), but they just looked like big grains of salt on most of the materials. The one that stood out was the yarn (shown above, enlarged). There it seemed to form large crystal structures that looked like they'd be ideal for the beginnings of stalactites. I think we found our crystal growing medium!

Stalagmites and stalactites, take 2

Our second attempt at making stalagmites and stalactites with salt crystals. This time we used a paper towel to connect the two jars filled with Epsom salt dissolved in water. The liquid did slowly travel up and across the paper towel, making the paper towel rigid, and we got some crystals forming below the paper towel, but nothing that looked like stalagmites or stalactites. We'll have to keep trying.

Stalagmites and stalactites

After visiting a cave exhibit at the zoo, we decided to try to make our own stalagmites and stalactites. We dissolved as much Epsom salt as we could into hot water and divided it into 4 empty baby food jars. We added different food color to each jar and then hung strings between them - some wool and some cotton. Each string was weighted down on either end with a paperclip. The idea was that the water/salt mixture would go along the strings and drop down near the middle where the strings dipped a little. Over time, this should cause some crystals to grow down from the string where the water was dripping from and grow up from the container where the water dripped to. Unfortunately, the liquid never made it up any of the strings, so we never got any stalagmites and stalactites. However, crystals started growing both around the rim of the jars and on the outside sides, and even around the outside base of the jars! We didn't expect that - and it saved our experiment from complete disaster.

Growing crystals

We tried to make crystals by dissolving Epsom salt in water. We heated water up in the microwave (so we could dissolve the salt at the table in plain view). After we dissolved as much salt as we could (with some undissolved salt sitting at the bottom of the cup) we microwaved it again. This dissolved the remaining salt and let us mix more in. We repeated this a couple times, added food coloring, and poured a shallow layer of the solution into a tupperware container. After letting it sit a couple days so the water could evaporate, we were left with some rather unimpressive crystals. It was essentially a somewhat sparkly layer of material. We'll have to work on making better looking crystals.