W: [IS.3 - Struggling Learners] “Today’s lesson is going to continue to focus on the concept of volume, along with mass and weight. We need to understand that there is a difference between mass and weight. After one of the activities, we will be able to discuss the similarities and differences between volume and how much an object weighs.”
H: “If I weighed each item on the table, which item would have the least amount of mass? Which item on the table would have the greatest amount of mass? Whenever I use the word ‘weigh’ in this lesson, I am referring to determining the amount of mass of an object or group of objects. Take a few minutes with the students around you to discuss your ideas about which items might have the least mass and most mass. Then record your answers on the Which Has the Greatest Mass? ranking sheet I passed out to you (5-4-3_Hook Activity- Ranking Sheet.doc). Be prepared to explain your thinking.” Once students are finished ranking the objects, have students share which object they think is the heaviest and why. Collect the student ranking sheets. This can inform you of the readiness levels of your students and their prior knowledge of mass. “Some of us agree about which item we think is the heaviest. Some of us disagree. I like how you supported your predictions with good reasoning. How could we show if our predictions are accurate or not?” (Allow students to respond. One response might be to use a scale to weigh the objects. Give students time to offer other suggestions.) Weigh the objects on the balance and record the mass for each object on a class chart for students to see. If a scale is not available, choose items that have their mass listed on them or weigh the items before the activity and share the mass of each during the activity. Ask students to rank the objects from lightest to heaviest while you arrange them in that order on the table. “Is this the order you ranked the items in originally?”
“I have a statement for you to think about. [IS.4 - All Students] If you think the answer is true give me thumbs up; if you think the answer is false give me thumbs down. Do weight and mass refer to the same thing?” Quickly scanning student responses to this question can give you a better awareness of your students’ level of understanding. Adjust the pacing of the lesson based on student readiness and need. The difference between weight and mass can become very scientific. The purpose is simply to expose students to the idea that indeed the words mass and weight are used interchangeably by many people, yet they are technically different. “It looks as though we have some disagreement. The correct answer is false. Do any volunteers who gave thumbs down want to share how they arrived at their thinking?”Allow students time to share their thoughts. Then using an overhead or document camera, show students the Weight and Mass Chart (5-4-3_Weight and Mass Chart.doc) and discuss it. To bring clarity to the difference between weight and mass, explain to students that if they went to the moon or traveled to Mars, they would still have the same mass, but their weight would be different because of the different gravitational pull on the moon and Mars.
Review the units used to measure mass in the customary English system of measurement and the metric system of measurement. If possible, have some items on hand so students can “feel” the difference in their mass. “Many people use the words weight and mass interchangeably, yet these two words mean something different. For the purpose of this lesson, we will be looking at the mass of different objects.”
“When measuring mass, we can use pounds and ounces or grams and kilograms. For the next activity, we are going to start with the customary English system of measurement. In a few moments, you will be assigned to a small group. There are stations set up around the room that you will be assigned to. Each station has a set of objects weighing one pound. Even though the objects weigh the same, the quantity may look different.”
E: “Now we are going to introduce volume into the discussion and see how that fits with what we already know. I would like you and your group members to look at the items; you can confirm that the objects do weigh one pound using the balance at each station if you like.” (If balances are not available, students will have to be reminded that the items weigh approximately one pound.) “Your task is to compare and contrast the different volumes of the objects. Remember from a previous lesson, volume is the amount of space occupied by an object or material. Your task will be to complete Part I of the activity sheet Is One Pound Always the Same?” (5-4-3_Is One Pound Always the Same.doc). If alternate items like school supplies (box of paper clips, pencils, erasers, chalk) are used, a blank template is available (5-4-3_Is One Pound Always the Same-Blank Template.doc).
While students are in groups, [IS.5 - All Students] monitor student interaction and responses. For those groups who are not as fluent in generating similarities and differences, ask questions to guide thinking.
- “Remember volume is the amount of space objects take up. [IS.6 - All Students] Which object has the biggest volume?”
- “Remember mass refers to the amount of matter an object has. Which object has the greatest mass?”
- “Are the answers to these two questions the same?”
- “Does an object with a larger mass always have a larger volume? Smaller volume? Give evidence to support your thinking with the objects at your station.”
- “What causes an object to have more volume?”
- “What causes an object to have more mass?”
R: “The objects used for this activity were measured using the customary English system of measurement. For your next task, using the balance at your station, I would like your group to measure the [IS.7 - All Students] objects in kilograms.” (Only ask students to measure the items in kilograms if balance scales are available. If balance scales are not available, refer to the chart and skip the actual measuring.) “Remember from the chart I shared with you earlier (put the Weight and Mass Chart back on the overhead or document camera), a kilogram is equivalent to a whole pineapple or a major league baseball. Mass can be measured in pounds or kilograms. Is a kilogram more than a pound? Or is a kilogram less than a pound? Talk with the students around you and discuss your thinking.”Allow students time to share their reasoning. (Some may say a kilogram is more than a pound because a pineapple is bigger than a pound of butter. Some may say a kilogram is less than a pound because they may not think a major league baseball weighs more than a pound.)
(If balance scales are not available, students can use a converter calculator listed in the Related Resources to determine how many kilograms are in a pound. Students should recognize that an object that weighs one kilogram is heavier than an object that weighs one pound.) “When you use the balance, be sure you measure the mass of each object in the set. Record the results you get on the Is One Pound Always the Same activity sheet, Part II. Once you are finished, complete the questions under the chart.” While groups are working, monitor student dialogue and the procedures used by the groups to weigh the mass of each set of objects in kilograms. If group measurements are inaccurate, ask the groups to repeat the procedure while you guide and monitor the group for understanding. Students may not come up with the exact conversion of 1 kilogram = 2.2 pounds for each set of objects due to errors like inaccuracy of the balance used or the original weight of an object may not have been “exactly” one pound. “I see that most groups are finished. Would you please discuss your findings with other groups and compare your results? Are you close?” (Give groups some time to dialogue with each other and then bring the class back together.) “What did you discover about the relationship between pounds and kilograms?” (1 kilogram is 2.2 pounds.)
E: The ranking sheet given to students at the beginning of the lesson can be a quick formative assessment that gives you some insight into how well students understand mass. Listening to student interaction and responses to questions is another way to informally assess student understanding throughout the lesson. When misconceptions become evident, be sure to clarify student thinking. Monitoring groups for accuracy during the weighing of objects and asking groups to repeat the process if they don’t determine the correct answer can rectify any misconceptions a group may have. This immediate feedback can facilitate student learning. “In today’s lesson, we briefly discussed the difference between weight and mass. We also looked at the relationship between mass and volume and the relationship between pounds and kilograms. Do objects with the same mass have to have the same volume? (no) Do objects with the same volume have to have the same mass? (no) Is a pound more or less than a kilogram?” (less; 1 pound is a little less than half a kilogram because 1 kilogram = 2.2 pounds)