Written by: Alicia Tinsley, Jessica Nordenson, Carly Hamilton
Grade Level: 2nd Grade
Second grade students have a basic understanding of solids and liquids. This base understanding may include the facts that water freezes (and turns into ice), ice melts, and the basics of what a liquid is versus a solid. To probe students’ prior knowledge we have students answer questions about temperature changes and how they affect liquids and solids.
To build on students’ prior thinking we want them to understand that when water is frozen and then thawed the amount of water stays the same. At the beginning of our lesson we ask the students what happens to water when it is put in very low temperatures. Students may say it gets cold, it freezes or it gets ice crystals. Then we ask the students what happens to the water when it freezes. We hope the students comment on the fact it gets harder, the texture changes, the ice seems bigger than the original amount placed in the freezer. However, we understand that the students may not note all of these.
To test our theories about what the water is going to do we are going to give each student a Dixie-style cup. They will fill the cup about halfway with water. Our students will then mark the original water level before the water is frozen. We will ask the students to talk with each other to see what they believe will happen to the water when it is frozen. They will place the cups in the freezer and then the next day they will take out the ice and talk with their groups about how the water has changed or not. We will then ask the students to mark where the ice comes to on the cup. The students will be asked where they think the water line will be when the water is thawed. Our plan is to prompt them with questions, such as asking them why they think the water line will be where they’re guessing. After the water has been thawed the students then see that the line of water is the same as the original line of water.
We will discuss with the class what happened overall. While we hope students will acknowledge that the amount of water never changed through the entire liquid to solid process, some students may not be able to make this connection. Although the water appearance may change, when the water becomes a liquid again the matter is still the same. As an extension, students might collect mass data throughout the freeze/thaw process.