The class builds a model. A model is a small copy of the real thing that works the same way.

1. Levi pours the warm salt water into the bowl.

The bowl of salt water is the ocean.

2. Leah stands the empty cup in the middle of the bowl.

The cup is the land.

3. Liana stretches the plastic wrap over the top of the bowl.

The wrap is the cover. It stands for the sky.

How to build the model, in three pictures.

4. Levi sets the bag of ice on the wrap, right over the cup.

The ice makes a cold spot, like the cold air high up.

5. Miss Ortiz puts the whole model in the sun on the windowsill.

The finished model, with its parts named.