String of spikes

Here's another fun science experiment from our book! For some reason, this experiment failed the first time, so we had to repeat it. Like the gummy bear experiment, this one teaches about osmosis, but the difference is that this time we saw what happened during osmosis when something else was dissolved in the water.

You'll need:
12 inches or so of cotton string (I used a shoelace with the aglets cut off)
baking soda
2 plastic cups
water

First, fill the plastic cups with water, then add about 1 tbsp of baking soda to each cup. Stir well (this wasn't included in the instructions, but I'm pretty sure that not stirring is why our experiment failed the first time :-).



Place one end of the string in each cup, and let the string and cups sit for two days. In the meantime, do not touch, jiggle, shake, or do anything else to the cups.



What happened after 2 days? The water was attracted to the string because it was drier, and it brought the baking soda with it! The baking soda collected on the string and formed small clumps that were hard to the touch.


Oliver had a good idea -- he wants to try the same experiment again, only substituting food coloring for baking soda. I guess we'll do that next! :-)