• Day 1: Have students determine their own mass and weight on Earth and on the Moon. Review students’ answers to the Measuring Mass worksheet.
• Day 2: Collect and assess the Practice Measuring Mass worksheet. Check students’ ability to use the triple-beam balance.
• Day 3: Students should understand how the balance was made, understand how to use the balance, and be able to discuss what could be measured using the balance. Students should be able to explain the difference between mass and weight.
• Day 4: Collect and assess the Mass Lab worksheet. During the lab, monitor each student’s ability to use the triple-beam balance properly to measure mass and to use the proper units to record mass.

Day 1

Note: Foundational knowledge of the properties of mass and weight and the units used to measure them is necessary in order to teach this lesson. For an introduction to mass and weight, refer to the following Web sites below:

• Weight or Mass?

http://www.mathsisfun.com/measure/weight-mass.html

• Mass and Weight

http://hyperphysics.phy-astr.gsu.edu/hbase/mass.html

Present the Mass Matters PowerPoint to introduce the concept of measuring mass (S-5-3-1_Mass Matters PPT.pptx). During the presentation, have students use the Mass Matters Notes worksheet to take notes (S-5-3-1_Mass Matters Notes and KEY.doc).

Be sure to explain the difference between mass and weight. Tell students that these terms are often confused with each other, but they are very different. “Mass is the amount of matter in an object, while weight is the force of gravity ‘pulling’ on an object. Mass stays the same everywhere in the universe, but weight changes depending on where the object is being weighed.”

Explain mass versus weight on Earth and on the Moon. The Moon is much smaller than the Earth so it has less force of gravity. An astronaut who weighs less on the Moon is still made of the same amount of matter. The mass of the astronaut does not change on the Earth or the Moon.

An object on the Moon only weighs about 1/6 of its Earth weight. For example, if you weigh 36 kilograms on Earth, your mass is also 36 kilograms. Your mass will still be 36 kilograms on the Moon, but you will only weigh about 6 kilograms! Have students determine their own mass and weight on Earth and on the Moon.

Demonstrate how to use a triple-beam balance to measure mass. Measure the mass of an object and lead students through the procedure for reading the mass on the balance. Then have students tell you the steps as you measure the mass of a different object.

Close the lesson by having students list the units for measuring mass and weight. See the example chart below.

Day 2

Liquid Masses Demonstration

Demonstrate how to measure the mass of a liquid in a container. Show students the parts of a triple-beam balance and explain how to use it as you measure the mass of an empty graduated cylinder. On the board, record the mass in a data table like the one shown below.

Into each of three graduated cylinders, pour an equal volume of one of the following: water, cooking oil, and corn syrup. Then, measure the mass of each graduated cylinder, and record the masses in the data table shown above. Calculate the masses of the liquids by subtracting the mass of the container from the mass of the container with liquid.

Check for understanding by asking students to turn to a partner and describe a step-by-step process for measuring the mass of sand in a beaker.

Practice Measuring Mass

Divide students in groups, with group size depending on the number of triple-beam balances that are available. Hand out the Practice Measuring Mass worksheet (S-5-3-1_Practice Measuring Mass and KEY.doc). Give each group the materials for the lab. As students conduct the lab, monitor their ability to use the triple-beam balance properly to measure mass and to use the proper units to record mass.

Close the lesson by reviewing the three follow-up questions on the lab worksheet.

Day 3

In preparation for the lesson, construct a balance to use as a model during the lab. Prepare materials for each lab group.

Warm-up question: “What is the difference between mass and weight?” Allow students a few minutes to answer the question in their science journals. Then explain, “Weight is different than the mass in an object. Mass stays the same, but weight changes depending on its location.”

Tell students that they can construct their own balances to measure mass. Explain what nonstandard measurement is (using units other than metric units). Tell students that people use nonstandard measurements every day (e.g., a “pinch” of spices in cooking, a “shovelful” of dirt when gardening). Show students your homemade balance and demonstrate how it works.

Divide students into groups of three to four for the lab. Hand out Make Your Own Balance (S-5-3-1_Balance.doc). Read through the procedure with students. Distribute materials and have students conduct the lab as you circulate around the room. Make sure that students understand that they are using nonstandard measurement to determine the masses of the items.

Notes for the lab: Make sure all paper clips can rotate freely in the holes. The balance will not work properly if the paper clips get stuck. When the balance is no longer swinging, the ruler should be hanging perfectly horizontal to the floor and the two cups should be the same exact distance from the floor. You may need to assist students in adjusting the lengths of the strings or the hanger’s hook until the balance is level. The balance can also be used to compare the weights of items to determine which has the most mass.

To close the lesson, allow students a few minutes to answer the following question in their science journals:

“If you used this mass balance on the moon, would the same item on one side require the same number of paperclips on the other side to balance it as it did on Earth?”

Discuss the answer: “Yes. Mass, the quantity of matter in an object, does not change when you change your location in space but weight does change.”

Day 4

In preparation for the lesson, prepare materials for each lab group.

In this lab, students will estimate the masses of various objects, and then use the triple-beam balance to measure the actual masses. Students may group items together to reach a targeted mass, such as three pennies for five grams, or they can select a single item. Note: Check estimates before allowing students to measure.

Divide students in groups, with group size depending on the number of triple-beam balances that are available. Hand out the Mix & Match Mass Lab sheet (S-5-3-1_Mix and Match Mass Lab.pdf) and materials to each group. Circulate during the lab to check students’ ability to use the triple-beam balance. Have students take turns with the balance to ensure that everyone gets practice.

Close the lesson by discussing the “Mass Challenge” at the end of the lab. Have students guide you as you demonstrate how to measure the mass of 100 milliliters of water using a graduated cylinder.

Extensions:

• In the Mix & Match Mass Lab, allow students needing opportunities for additional learning to have extra time to practice measuring the known masses until they are competent at using the triple-beam balance. Reduce the number of targeted masses in the data table (e.g., 1, 10, 50, and 100 grams).
• Students who are going beyond the standards can assemble a set of objects that they think are equal to 10, 20, and 30 grams and then measure them on the triple-beam balance. Have them record their predictions and measurements in a data table.  
• Have students write a summary of an experiment in which they would need to measure masses of objects.