Chemistry can be taught at a younger age, and something as simple as the chemistry of water. I remember doing the activity with putting drops of water on a penny and trying to figure out why the water created a dome-like affect rather than going over the edge of the penny. Then, we were able to learn about adhesion and cohesion of water. This was something that the teacher made simple, but we still used the key terms. I remember doing this activity, and was able to remember those words when I went into middle school.
Another activity with water would be using the new idea of nanotechnology, which is hydrophobic. Here is a short video about how to make things water
repellent, and this could be very interesting to students. (https://www.youtube.com/watch?v=3ayRImPvcQU) You could talk about how if this is applied to clothes how they could be water proof, and what other items we could apply this waterproof coating to.
I hope this helps,