Here are pictures of how our experiments ended up:
The water has started to evaporate and the salt is left on the popsicle stick!
This spider was a BIG hit! They have been so excited to check on it every day. It hasn't grown since the first 72 hours, but they still find it very exciting to look at. A simple absorption activity! I had to move him to a bigger container as he was getting too squished in the plastic cup.