Weight, Mass, & Gravity

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Objective

SWBAT to explain the relationships between weight, mass, and gravity.

Big Idea

In this lesson, students will explore why an astronaut can jump higher on the Moon than on Earth by researching weight, mass, and gravity.

Lesson Overview

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):

1. Focus

2. Explore

3. Reflect

4. Apply

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. 

Unit Explanation

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 presenting a scientific phenomena, astronauts can jump higher on the Moon than on Earth. Students will then explore gravity, weight, and mass by choosing from a variety of resources. At the end of the lesson, students will reflect and apply their new understanding of weight, mass, and gravity to explain why astronauts can jump higher on the Moon.

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 objects is directed down.

Scientific & Engineering Practices

For this lesson, students are engaged in Science & Engineering Practices 1 and 7.

Science & Engineering Practice 1: Asking Questions and Defining Problems: The goal is for students to inquire about weight, mass, and gravity and to discover cause and effect relationships between the force of gravity and the height of an astronaut's jump. 

Science & Engineering Practice 7: Engaging in Argument from Evidence: Today, students will be developing arguments and reasoning by collecting evidence through research. 

Crosscutting Concepts

To relate content across disciplinary content, during this lesson I focus on Crosscutting Concept 2.

Crosscutting Concept 2: Cause and Effect: In particular, students will be examining the relationships between the force of gravity, weight, and mass. Students will determine that the higher the force of gravity on a celestial object, the higher an astronaut's weight. Students will also discover that an astronaut's mass does not change when he/she travels to other celestial objects. 

Disciplinary Core Ideas

In addition, this lesson also 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)

ELA Integration

To add depth to student understanding, when I can, I'll often integrate ELA standards with science lessons. Today, students will work on meeting CCSS.ELA-LITERACY.RI.5.7: Draw on information from multiple print or digital sources, demonstrating the ability to locate an answer to a question quickly or to solve a problem efficiently. In this lesson, students will be using multiple resources (both print and digital) to locate the answer to questions about gravity. 

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!  

Focus

20 minutes

Video of a Jump on the Moon

I show students the first 40 seconds of the following Lunar Olympics Video: 

Jumping on Earth

I then grab two meter sticks to help students visualize a four foot jump on the moon: Marking a Jump on the Moon. I ask a volunteer to demonstrate how high people can jump on Earth. We first mark the child's reach on the board. Then the child jumps up as high as possible and we mark how high he can jump and reach. We measure the difference between the "reach measurement" and the "jump measurement" to calculate the height how high a person can jump on Earth: Marking a Student's Reach & Jump

We then discuss the differences between the astronaut on the moon and the student jumping in the classroom. I hand the student a 20 lb backpack and explain that an astronaut's suit weighs 180 lbs. Every student wants to hold the backpack! I ask students to turn and talk about the number of 20 lb backpacks are equal to an astronaut's suit. After discussing, students determine it will take 9 backpacks to equal the weight of a space suit. 

I want to inspire interest in today's lesson and capitalize on student curiosity, so I pose an authentic question: Why can an astronaut jump over four feet on the moon with a heavy space suit on when we people can only jump about 20 inches on Earth? Students offered great ideas, based on their prior knowledge and experiences.

Weight & Mass Process Grid

Prior to the lesson, I project this Mass & Weight Beginning Process Grid to easily copy the outline, headings, and clipart: Process Grid Teacher Example

At this point, I provide students with some background information on weight and mass to build interest and student investment by writing in the font in red and blue. I complete the Earth, Moon, and Space columns as I explain that the weight of an astronaut in a space suit is about 1601 Newtons on Earth but an astronaut's weight on the moon is 267 Newtons and 0 Newtons in space. I also explain that an astronaut's mass is 163 kg on Earth, 163 kg on the Moon, and 163 kg in Space.

Class Discussion

As a class, we discuss the questions students would like to investigate further and possible answers: Student Questions.

Explore

40 minutes

Narrowing Research Questions

To ensure focused learning, students decide to research the following questions: 

1. What is the difference between weight and mass? 

2. Why can an astronaut jump higher on the moon than on Earth?

Setting Up Journals for Taking Notes

Students record the above questions in their student journals and they leave room for notes at the bottom of the page. Here's my example: Teacher Notes Template.

Resources

To explore student questions further, I provide students with a variety of resources to research with their science teams. I want to make sure to provide students with choices and I also want to teach to a variety of learning styles. During this time, all students are researching and taking individual notes, but reading and watching sources together as a group. Some groups choose to work together while others choose to work more independently. Close collaboration within a group setting inspires great conversations about gravity!

I provide students with the following resource options. Prior to the lesson, I printed the texts on different colored paper (Sources 1-4 on the Board) and I set up four computers in the classroom for viewing the videos, two for each video source (Source 5 Video and Source 6 Video). Students choose the order in which they want to research each resource. Most students are able to interact with every resource, depending on the depth of conversation between science teams. 

1. Gravity (video)

2. Weight and Mass (text)

3. Weight or Mass? (text)

4. Apparent Weight (text)

5. Mass (text)  

6. Mass & Weight Introduction (video)

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

  1. Why do you suppose ____? 
  2. What have you found so far? 
  3. Has your thinking changed? 
  4. What evidence do you have? 
  5. How did you decide ______?
  6. Has your thinking changed? 
  7. What conclusion can you draw about ____?

Student Conferences

During this conference, Finding the Answers to Questions, a student does a beautiful job explaining the meaning of weight and mass. This is such a great reminder that students should be knowledge-seekers instead of relying on the teacher for all the answers!

Here, Comparing Weight & Mass, another group discusses the difference between weight and mass. I grab a pair of scissors to connect these abstract concepts with an everyday object. 

In this video, Comparing the Earth to the Moon, I was excited to hear students developing an explanation of why gravity is greater on Earth than on the moon (because the mass of the Earth is greater). Gaining a deeper understanding of "why" will help these students learn beyond the memorization of facts. 

Student Work

Here are some examples of student notes during this time: 

Reflect & Apply

20 minutes

Sharing Findings

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 the front carpet to share what they've learned. 

Process Grid

Looping back to the original process grid, we complete the remaining columns. I hold my notes (Mass & Weight Process Grid) in my hand to use as a guide. The grid will eventually look like this: Completed Process Grid. Instead of providing the information for students, I ask students to share their thinking, based on their research. To match the wording in my notes, I ask, "So what you're saying is that... (and then I would write the words straight from my notes)" While we complete this chart together, students add information to their own notes. In hindsight, perhaps I should have written the notes in the student's words so honor their thinking and research. 

Column 1: Definitions

We begin by discussing the definitions of weight and mass. Students did a great job defining both terms. I summarize student thinking by recording bulleted notes. One student explains that weight is the strength of the gravitational pull on an object. While another shares that mass is the amount of matter in an object.  

Columns 4 & 5: Measuring Weight & Mass

Next, we discuss the standard ways to measure weight and mass. We talk about how pounds is a Customary Unit of Weight, however, scientifically speaking, Newtons are the correct measurement of force, therefore, Newtons are used to measure weight because weight refers to the force of gravity on an object. 

We also talk through the importance of using a balance scale to measure mass as we can use this same tool on the moon and the mass would be the same. On the flip side, if we took a platform scale that measures kilograms, we would be measuring the pull of gravity instead of the amount of matter in an object. 

Drawing Conclusion

To bring closure to the lesson, I ask students what conclusions we can draw about gravity, weight, mass, and an astronaut's jump on the Moon verses the Earth. We made the following list on the board: Drawing Conclusions List.

This was a great way to quickly summarize student findings today!