Have students:

• Collect and weigh their mini-lakes.
• Record the weight in the table and on the graph in their Science Notebooks.
• Record other significant observations.

Students should continue to weigh their mini-lakes daily if possible and record the data. When all of the water has evaporated, they can stop.

• We know how much water we put in the mini-lake so when the mini-lake loses that amount of weight, we'll know the water is gone.
• We see if there's any water left and see if the material on the lake bottom feels dry.

Point out that, as they did when they dissolved salt, students are using weight to determine if and how much matter is present.