This past week we learned about caves. My original thought was to create our own stalactites, but because they move from room to room and each student needed two cups to suspend their string, I decided that was too complicated for our set up. I did find a cave idea that sounded fun but was cost prohibitive. I did find an idea to make our own limestone caves and that is the one I chose.
We needed sugar cubes (also called sugar dots, even though they are square-go figure), straws, plates, water, toothpicks, scarves, instructions. The scarves were for a game we played after we made our caves. Some of the kids had never seen sugar cubes/dots before, so it was fun to see their reaction as they had no idea sugar came in that form.
On each plate each child had 10 cubes. They had to stack them and I had to ask some of them if they knew the difference between stacked and a line. In order for this to work, they had to be stacked.
After everyone had their cubes stacked, we dipped straws in the water and dripped the water onto the stack. The water drops needed to be dropped on the same area of the stack in order to make their cave.
Here they are dripping water on to their caves. Toothpicks could have been used for this too but since straws are longer I went with those. We could have used toothpicks to hold the plates up slightly at one end, but I ended up not doing that and we did still get our caves.
Here you can see one student dripping water on her cave.
Here are a few of their finished caves:
Some of the kids seemed disappointed that they did not have caves so I told them that they had to be sure to drip water in the same spot on their stack, and that it does take more than a few seconds for results to appear. One of my helper moms also pointed out that if the water was put on the cubes and not pooled on their plate away from the cubes, there would be a better chance of success :).
I have two cups out too-one with salt and one with water. The one with salt was simply to make my life easier so that I had enough for each class without having to go back to the kitchen. The water was cool and I put some salt in it at the beginning of class so we could see how crystals dissolved and how in cool water it takes longer.
I also told them that is how stalagmites and stalagmites form-salt crystals in water and I also told them that just because we don't see the crystals any longer does not mean they are not there. We don't see air or wind either, but they are still there. In caves they can form and reform.
Then we played a game and that is when things got too busy for me to take pictures. The people with scarves were water particles. The original idea called for headbands but since I had scarves and they don't break as easily as a scarf I used those. Everyone else was a salt particle. The salt particles had to hold hands and then see if they could still hold hands while going through the water particles. Most of the time they ended up breaking apart (at least some of them) I explained that this is what happens to salt or sugar in a cool or hot drink and what happens with the stalactites. When you look at them (or icicles) you can see that they are thicker at the top than at the bottom and that they generally have a taper. It is thicker at the top because more particles were able to stick closer together while forming. Less particles were able to stick together at the bottom and also gravity helps pull the bottom part down adding to the taper shape.
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