I started out by reading Heather Fell in the Water by Doug MacLeod and Craig Smith.
Then we did a floating egg experiment, which not only allowed us to talk about "sink" and "float", but also set them up to experiment on their own when we went to the stations.
I got the idea from here, though I simplified it to just be about an egg (click the link for other fun ideas!). We tried an egg in fresh water and then added salt bit by bit until the egg floated. While I poured and mixed, we talked about density and how much salt it might take to make the egg float.
Once we got the egg to float, it was off to the stations!
To prep the stations, I put plastic tablecloths over each table and then layered a beach towel (from home) on top of that. (Hence the colorful pictures...). This kept the mess - or, in this case, the wetness - from going everywhere. Just remember to bring a bag to hold all the wet towels you'll be taking home to wash.
1 - Swimming Raisins
Unfortunately for our first station, this one was a bust. Supposedly, a raisin will sink in regular water, but will rise and fall with the bubbles in sparkling water. We tried it a few different ways, but this one never quite took off. I'm gonna go with: it's the "learning about the scientific method" station...
I put out a dozen plastic containers of different sizes and heights and capacities and asked the children to pour the water from one container to another. Even though the shape of the water changed, the volume remained the same. Also, pouring water is fun.
3 - Water Absorption
One of my co-workers donated a bunch of Talenti gelato containers and they are awesome! (Both the jars and the co-worker). I've used them for all sorts of things, but this time I put out sponges in different sizes and asked the children to put a sponge and a little water into a container, seal the container, and see if their sponge could absorb the water as they shook the container.
4 - Sink or Float
This station was the most fascinating to the kids. I had bowls of water, a worksheet, and a ton of objects for the children to test. I also put out salt in case they wanted to try to make something float. This station got the best conversations between caregivers and children as they tried to guess what would happen and then tested it out. Also, as you probably already know, dropping things in water is fun.
5 - Water-resist Painting
I pulled out my white crayons for this one. The kids drew something with the white crayon on white paper and then painted over it in watercolor paint. Above, you can see the fish emerging through the paint. A lot of kids really liked this one, though they sometimes had their parents draw the first part because the white on white was too complex.
This was one of my favorite labs - simple concepts but all fun to play with (except the raisins) and minimal mess. I'll be repeating this one.