Note: It is important to use the correct units when referring to mass and weight. Strictly speaking, the metric unit for mass is kilogram and the metric unit for weight is the Newton. In the U.S. customary system, there is no unit for mass and the unit for weight is pounds.
Advance Preparation: Gather all materials for the Scales and Balances Mass and Weight demo and the “Story of the Golden Crown” before class. Also, read through the “Story of the Golden Crown” to become familiar with how it relates to acting out the story.
Day 1
Demo: Scales and Balances Mass and Weight
Begin the lesson by asking students how many of them have played on a teeter-totter (seesaw). Ask a student to describe his/her experience on a teeter-totter. Have students describe what would happen if completely identical twins sat on either side. (The teeter-totter would be balanced.) Ask, “What if one of the twins was holding a heavy rock?” (The side with the twin with the rock would go down.) “All teeter-totters are similar to a scientific tool that can be used to measure something. Do you know the name of that tool?” (It is a balance.) “What do you have in your home that is similar to a balance?” (a scale/bathroom scale)
Show students a triple-beam balance and electronic scale and demonstrate how to use each one. Give students the Scale and Balance worksheet (S-5-4-1_Scale and Balance and KEY.docx). Discuss each question and have students record the answers on the worksheet.
K-W-L Chart: Matter and Motion: “K” and “W” Sections
Give students copies of the K-W-L Chart (S-5-4-1_KWL Chart.pdf) or have them create a K-W-L chart in their notes. Have them write in Matter and Motion next to “Topic.” Have them fill in the “K” and “W” columns. For the “What I Know” column, provide definitions for the terms: matter, mass, weight, and volume. Have students add to the “What I Know” column and also complete the “What I Want to Know” column independently. An example is provided below:
K
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W
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L
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What I Know
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What I Want to Know
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What I Learned
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Matter is anything that has mass and takes up space. Three common states of matter are solid, liquid, and gas.
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How are mass and weight different?
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Mass is the amount of matter in something.
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Would your mass be different on another planet?
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Weight is the measurement of the gravitational force acting on an object.
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Would your weight be different on another planet?
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Volume is how much space an object takes up or can contain (hold).
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Why is your weight different on another planet?
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Lab Activity: Mass and Weight
Assign students to small groups for the lab and distribute the Mass and Weight Lab worksheet (S-5-4-1_Mass and Weight Lab and KEY.docx) and materials to each group. Read through the procedure and answer any questions. Have students complete the lab and answer the questions.
K-W-L Chart: “L” Section
Have students complete the “What I Learned” column of the K-W-L chart, based on what they learned in this lesson about matter, mass, weight, and volume. Sample answers are provided below:
KWL Chart Answers:
What I Learned
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Mass is the amount of matter in something. Weight is the pull of gravity on that mass. The more mass, the more matter something has in it.
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Your mass is the amount of matter in your body so it would stay the same on another planet.
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If another planet had the same exact gravity, your weight would stay the same. But that is very unlikely. Your weight changes from planet to planet with different gravities.
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Your weight is different because the pull of gravity is different on different planets—more gravity, more weight, and vice versa.
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Day 2
The Mass vs. Weight Exploration
Give each student a copy of the Mass vs. Weight Exploration worksheet (S-5-4-1_Mass vs Weight Exploration.docx). Have them complete the worksheet independently. Go over the answers with the class.
Reading: “Story of the Golden Crown”
Have students read “Story of The Golden Crown” (S-5-4-1_Story of the Golden Crown.doc).
Act out “Story of the Golden Crown.” Select two volunteers to portray the king and Archimedes. Introduce yourself as the goldsmith. First, have the king use an electronic scale to measure the mass of his original quantity of gold, represented by a chunk of cheese. Then, have the king give the goldsmith (you) the “gold.” Turn your back to the king as if working in secret. Use a knife to remove a small amount of the cheese and replace it with soft modeling clay. Tell students that the modeling clay represents the silver added to the crown. Measure the mass of the cheese with modeling clay. Adjust the amount of modeling clay until the mass is equal to the mass of the king’s original quantity of gold. Return the “crown” to the king. Have the king act suspicious that the goldsmith replaced part of the gold with silver. Tell the king to give the crown to Archimedes (played by the other student) to test its purity. Have Archimedes place a quantity of “gold” (which is represented by the other piece of cheese) equal to the original amount of gold in a bowl of water and note how much the water rises in the container. Then, Archimedes should place the “crown” into the water and notice that the water level is higher. Have student volunteers return to their seats. Post the following questions on the board and have small groups of students discuss the answers:
“Why did Archimedes place the crown in water?”
“If the crown weighed the same as the gold, why did it take up more space in the vessel?”
“Was the crown a fraud?”
Hold a whole-class discussion about the questions. Have students relate the terms mass, weight, and volume to the story. If needed, guide students to an understanding that a larger volume of silver must be added to the crown to equal the mass of the gold. The class should conclude that the crown was indeed a fraud, because the crown had the same mass as the gold but took up more space. That means that the crown was made of a lighter material (i.e., silver).
Review the lesson by asking a couple of questions. Post student responses on an overhead or chalk/dry-erase board. Have students record the answers in their notes.
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“What is the difference between mass and weight?” (Mass is the amount of matter in an object while weight is the pull of gravity on that mass.)
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“Are mass and weight the same on another planet?” (Your mass remains the same while your weight changes.)
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“What makes your weight different on another planet?” (Different planets have different gravities, so the pull on the mass changes. The strength of a planet’s gravity depends on its mass. The greater the force of gravity, the greater your weight.)
Extension:
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For students who may need opportunities for additional learning, verbally accept their responses to the lab questions.
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For students who may not be able to perform the physical aspects of the lab activity, select a teacher’s aide or a pair of students to assist them during the lab (i.e., students can direct the aides to manipulate lab equipment).
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On Day 2, students ready to go above and beyond the standards can take what they have learned about mass and learn the formula for density.
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Have them relate the concept of density to the “Story of the Golden Crown.” Provide students with varying masses and volumes and have them solve for density.
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For students who may need opportunities for additional learning, post the follow-up questions for the “Story of the Golden Crown” on the board and read through them aloud before students read the selection. Have students highlight or underline any parts of the story that they do not understand as they read. Clarify these sections before the students’ group discussion.