Osmosis.

With my phone unable to make blogging easier, I obviously went on a bit of a hiatus. Some ideas came to me during that time for good posts, but some were a bit time dependent, and now the moment is gone.

I did a neat demo a couple weeks ago with my science 10's about how water moves across membranes. In the past, I've used eggs, but it's really messy... you need to dissolve the shell off first (which takes 24 hours in vinegar), and then wait minimum 24 hours to see if the eggs change size in different concentrations if salt water. But the shell-less eggs are very fragile, which leads to the messy part.

This year, I used gummy bears. Already this demo is cooler. There is the possibility of eating something. Basically, if you put a gummy bear in tap water, it will swell up. And fast.

What happens is there is a high concentration of sugar inside the gummy bear, and no concentration outside. This difference in concentration is known s a concentration gradient, and typically what would happen is the sugar would diffuse out of the gummy bear (diffusion is movement of particles from an area of high concentration to low). However, gummy bears are made with gelatin, which does not really dissolve in water very well, and the gelatin traps the sugar inside. Since the sugar can't get out to equalize its concentration, water flows in.

The result? Monster gummies. Within an hour you will notice a difference. The ones in this picture were left for about 8.

Green is original size.