Measuring the Weight & Mass of Pennies
Lesson 2 of 19
Objective: SWBAT measure the weight and mass of objects.
Inquiry Based Instructional Model
To intertwine scientific knowledge and practices and to empower students to learn through exploration, it is essential for scientific inquiry to be embedded in science education. While there are many types of inquiry-based models, one model that I've grown to appreciate and use is called the FERA Learning Cycle, developed by the National Science Resources Center (NSRC):
A framework for implementation can be found here.
I absolutely love how the Center for Inquiry Science at the Institute for Systems Biology explains that this is "not a locked-step method" but "rather a cyclical process," meaning that some lessons may start off at the focus phase while others may begin at the explore phase.
Finally, an amazing article found at Edudemic.com, How Inquiry-Based Learning Works with STEM, very clearly outlines how inquiry based learning "paves the way for effective learning in science" and supports College and Career Readiness, particularly in the area of STEM career choices.
In this unit, students will develop an understanding of gravity while focusing heavily on the 5th Grade Engineering and Design standards. In the first few lessons students will explore the relationships between gravity, weight, and mass. Then, students will apply their understanding of gravity to engineer and design parachutes and roller coasters.
Summary of Lesson
Today, I will open the lesson by demonstrating how to measure the weight and mass of objects using a spring scale and balance scale. Students will then explore the weight and mass of groups of pennies. At the end of the lesson, students will reflect and apply their new understanding of weight and mass by constructing a line graph and making observations.
Next Generation Science Standards
This lesson will address the following NGSS Standard(s): 5-PS2-1. Support an argument that the gravitational force exerted by Earth on an object is directed down.
Scientific & Engineering Practices
For this lesson, students are engaged in Science & Engineering Practices 4 and 5.
Science & Engineering Practice 4: Analyzing and Interpreting Data - Students will analyze the data collected during their investigation by constructing a line graph.
Science & Engineering Practice 5: Using Mathematics and Computational Thinking - Students will make quantitative predictions about weight and mass by analyzing mathematical relationships.
To relate content across disciplinary content, during this lesson I focus on Crosscutting Concept 1.
Crosscutting Concept 1: Patterns - In particular, students will identify the relationship between weight and mass, based upon collected data. They will also use observed patterns to make predictions.
Disciplinary Core Ideas
In addition, this lesson aligns with the Disciplinary Core Idea, PS2.B. Types of Interactions: The gravitational force of Earth acting on an object near Earth’s surface pulls that object toward the planet’s center. (5-PS2-1)
Choosing Science Teams
With science, it is often difficult to find a balance between providing students with as many hands-on experiences as possible, having plenty of science materials, and offering students a collaborative setting to solve problems. Any time groups have four or more students, the opportunities for individual students to speak and take part in the exploration process decreases. With groups of two, I often struggle to find enough science materials to go around. So this year, I chose to place students in teams of three! Picking science teams is always easy as I already have students placed in desk groups based upon behavior, abilities, and communication skills. Each desk group has about six kids, so I simply divide this larger group in half.
Gathering Supplies & Assigning Roles
To encourage a smooth running classroom, I ask students to decide who is a 1, 2, or 3 in their groups of three students (without talking). In no time, each student has a number in the air. I'll then ask the "threes" to get certain supplies, "ones" to grab their computers, and "twos" to hand out papers (or whatever is needed for the lesson). This management strategy has proven to be effective when cleaning up and returning supplies as well!
Lesson Introduction & Goal
To begin, I invite students to join me on the front carpet so that all students can have a closer look at a spring scale and balance scale. I introduce today's learning goal: I can measure the weight and mass of objects.
To build off of yesterday's lesson, I review the meaning of gravity, weight, and mass using the following vocabulary using these posters: Gravity Vocabulary Poster, Weight Vocabulary Poster, and Mass Vocabulary Poster. I want to make sure students are using precise language when discussing each of these concepts. I hang the posters on our science wall and students often refer to the wall when developing their own scientific explanations.
I continue by briefly reviewing key ideas from yesterday's lesson. We discuss how an astronaut's weight on Earth is greater than on the moon because the Earth has a greater gravitational pull. We also talk about mass and how the mass of an astronaut does not change on the Moon because mass is the measure of matter. The only way an astronaut's mass would change is if he/she loses weight or takes part of the space suit off!
I want to inspire interest in today's lesson and capitalize on student curiosity, so I compare the spring scale and balance scale by using a poster Spring Scale & Balance Scale Comparison Chart and by modeling how to use a spring scale and balance scale. I first hold up two index cards (Use for Measuring Cards), one is labeled, "Use for Measuring Weight" and the other is labeled, "Use for Measuring Mass." Reflecting upon yesterday's lessons, students agree to place the "weight card" on the spring scale side of the poster and the "mass card" on the balance scale side of the poster.
The Spring Scale
I hold up a 2.5 N spring scale and I explain the parts of the spring scale. Looking back, I should have referred to it as the "spring scale system" and specifically used the words "subsystem" and "function" to explain each part. After discussing each part, I explain how to calibrate the spring scale by adjusting the nut until the indicator is at the zero line. Next, I model how to measure the weight of a marker, pair of scissors, and a glue bottle by hanging a plastic baggie from the hook. Prior to the lesson, I place Labels to label the weights of each object on the poster: Labels on Chart. It was important for students to learn how to use the scale to determine the weight of objects, especially because the number of Newtons would be in decimal form. (As a side note: I will teach students how to say decimal numbers later on. Right now, I don't want to overwhelm students during the first few weeks of school and am okay with students reading 4.21 as "four point twenty-one" or "four point two-one." I do make the connection to money often throughout this lesson.)
The Balance Scale
Next, I use the Spring Scale & Balance Scale Comparison Chart to teach students the parts of a balance scale. As often as possible, I make connections between the two scales, such as the fact that both scales can have an adjustment knob for calibrating the scale to zero. Instead of modeling how to weigh all of the above objects, I show students how to find the mass of just the marker using the balance scale and a mass set.
By the time I am finished modeling, students can't wait to get their hands on these tools! Heres' what the poster looked like at the end of this time: Added Notes & Labels on Chart.
I ask students to return to their desks and I pass out Pennies Recording Sheet to each student. I explain: In the first column, I'd like for you to find the weight of 9 pennies. Which measuring instrument will you use to find the weight? (spring scale) In the second column, I'd like for you to find the mass of 9 pennies. Which measuring instrument will you use to find the mass? (spring scale).
In each science group, there are three students. For gathering supplies, I ask students to number off (1, 2, and 3). I ask the #1 students to get a 2.5 N spring scale and baggy. I ask the #2 student to get a balance scale. And I ask the #3 students to get mass set and a bag of pennies. This really helps with avoiding crowds at the supply counter and it also ensures that all students are involved, right from the start! As students return with supplies, they immediately begin counting out pennies. I remind students, "Don't forget to calibrate your scales!"
Monitoring Student Understanding
Once students begin working, I conference with every group. My goal is to support students by asking guiding questions (listed below). I also want to encourage students to engage in Science & Engineering Practice 7: Engaging in Argument from Evidence.
- What patterns have you noticed?
- Why do you suppose ____?
- What have you found so far?
- Has your thinking changed?
- What evidence do you have?
- How did you decide _____?
- Has your thinking changed?
- What conclusion can you draw about ____?
During this conference, Using Patterns, I encourage students to begin using patterns to check the results of their investigation. For example, if 9 pennies weighs 0.25 N., then it makes sense that 18 pennies would equal 0.5 N.
I loved how this students noticed an error with calculations and struggles with the fact that all measuring tools are not perfectly accurate, especially those often used at the elementary level: Imperfect Measurements.
To challenge this group, I ask them to use the balance scale to explain why the mass of an object stays the same on the moon: Why Does Mass Stay the Same. I love how they are starting to grasp the fact that the matter of an object will stay the same (as long as nothing is taken away or added).
Reflect & Apply
At the end of this investigation, many student data tables look similar to this student's: Data Table. In actuality, if an object weighs 0.25 N, it should have a mass of 25 grams. I could have avoided this discrepancy by asking students to use the backside of the spring scale (which has a gram scale) to measure mass. However, I want students to learn that a balance scale can be used on any planet (regardless of the gravitational pull) to determine the mass of an object. On the other hand, a spring scale would not provide an accurate reading of mass on the moon because it relies on the force of gravity to pull the load down.
Now that students have built meaning and understanding by observing, questioning, and exploring, it is important to provide students with the opportunity to share their findings. For this reason, I invite students to help complete a projected class data table: Class Data Table. Most students were able to provide the correct weight and the majority of groups came within a few grams of the the correct mass. When finished, we discuss the relationship between the Newtons and grams. One student points out, "You just take way the decimal point to get the number of grams." I ask: What would we multiply 1 Newton by to get to 100 grams? (100) Together, we determine the rule of the table: n (the number of Newtons) x 100 = g (the number of grams).
Making a Line Graph
To help students visualize the relationship between weight and mass, I provide guidance on Making a Line Plot. We first complete the scale on the x-axis. How many pennies did we weigh to begin with? (9) If the first line represents 9 pennies, what should the next line represent? (18) Students then complete this scale on their own.
We then discuss the y-axis scale. If the y-axis represents the weight of pennies in Newtons, what do you think we should start with? (0.25) What should come next? (0.5) Again, students complete the scale on their own.
Next, I model how to begin plotting points. How much did 9 pennies weigh? (0.25 N.) I show students how to place a point at (9, 0.25). We discuss the next point and soon, students were able to continue on their own. When finished, we drew a line to show the relationship between the number of pennies and weight.
As students finish graphing their data, I ask students: What do you notice when you look at your graph? What did you learn today?
A wonderful conversation took place. Below are some of the students' comments:
Here's a Student Example of the graph and line plot. You can see that some erasing was involved in order to have accurate measurements for the line plot. Students also extended the line to determinate the weight of 54 pennies and 63 pennies. Using patterns to make predictions is a key math and science practice.