Explain to students that learning to measure volumes takes practice. Today they will practice measuring different liquids. They will use a container called a graduated cylinder to measure liquids. Graduated cylinders have numbers on the side that help you determine the volume. Volume is measured in units called liters or fractions of liters called milliliters (ml). Students need to follow the directions on the lab sheet carefully. Remind them that you will be checking how they measure as you move about the room.
On the board show students a drawing of a graduated cylinder with a meniscus. Demonstrate where you would take the measurement. Ask them to work over the dish provided to make clean-up easier. Styrofoam meat trays work well for this.
Show students the beaks on both the graduated cylinder and the beaker. Tell them that they should use the beak to pour from.
Distribute the lab sheets. Ask students to complete the prediction and then to follow the directions on the lab sheet. It is difficult for students to measure because they are usually not patient. It is important for them to keep trying.
When the lab is completed, ask the students to answer the conclusion.
Students should notice that the addition of salt does not effect the volume of the water. This is because as the salt dissolves, its molecules fill in the free spaces between the water molecules. The volume would change if enough salt was added to saturate the water. Be sure to use soapy water to clean the glassware