Sinking and floating

After studying and comparing solids and liquids, we are thinking about sinking and floating. Before doing any experiments, we developed common definitions for the two terms, so that no matter who does the test, we would all get the same result. We decided that an object that touches the bottom but has a part of it sticking up above the water is too big to test.

Next, we tested a lot of objects. For each one, we predicted if we thought it would sink or float, and explained why. Then we tested. We started to collect all of our data on this T chart:

We then talked about why we think the objects that floated or sank did so. We used sentence frames to make sure we explained our thinking with the word because.

We also thought about displacement. All matter takes up space, and two pieces of matter cannot be in the same space at the same time. So, when you put a solid object into water, it displaces some of the water, and pushes it out of the way. To show this, we took a big plastic tub and filled it all the way to the top. Mr. MacLellan didn't even spill too much getting it to the rug.
We put a small object, a paper clip, into the tub. It displaced so little water, we didn't even see any spill over the sides. Then, we put a rock into the tub. A lot of water spilled over the sides! We then measured how much water spilled out. The little rock displaced 6 cups of water!
Then, we put a big rock in the tub! A little tiny bit of it was sticking out of the water, so it was too big to test, but it displaced more than 11 cups of water.

This week, we took materials that sink and tried to make them float. Some groups tried to make a rock float, and others tried to make a ball of clay float. We tried many different strategies, but most groups ended up taking materials that did float and building a raft. Here, we are testing our designs:

Next, we will be building boats!