Applied Science - Science and Math (3B)
Lab 

   
OBJECTIVES:
  • Measuring volume using a graduated cylinder.
  • Recording volume.
VOCABULARY:
  • graduated cylinder
  • measure
  • volume
MATERIALS:

Students learn to measure liquids in a graduated cylinder.

  

BACKGROUND:

Measuring liquid is difficult for students.  Practice makes students more proficient, but not experts.  It takes experience and skill to measure when using a graduated cylinder.
  
Discuss the divisions of measurement on your graduated cylinder.  A graduated cylinder measures in milliliters, which is a measure of volume.  The English system equivalent is pints, quarts, and gallons.  It is much easier to measure in milliliters, because it is already divided into the decimal system for you.  Just as students measured using metric with the left side of the decimal point centimeters and the right millimeters, the same is true for metric volume.
 
Measuring with a graduated cylinder is complicated somewhat by a meniscus.  A meniscus is the curvature of the surface of the water.  Water "sticks" to the walls of the graduated cylinder, but only on the sides and not the middle.  When students look at the surface, the water level is not straight.  Measurement should be at the lowest point (see figure to the right).  Students need to read the meniscus at eye level in order to get an accurate reading.  Students should place the graduated cylinder on the table and then lower their heads to be able to read the meniscus at eye level.

PROCEDURE:

  1. 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.
      
  2. 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. 
      
  3. Show students the beaks on both the graduated cylinder and the beaker.  Tell them that they should use the beak to pour from.
      
  4. 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.  
      
  5. When the lab is completed, ask the students to answer the conclusion.
      
  6. 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 containing oil. 

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