Science · 7th Grade · Energy and Matter in Motion · Weeks 1-9

Potential Energy: Stored Energy

Students explore different types of potential energy (gravitational, elastic, chemical) and how they are stored and released.

• Common Core State Standards
• MS-PS3-1

About This Topic

Potential energy is the energy an object holds because of its position, shape, or chemical composition. This topic builds directly on MS-PS3-1, asking students to construct explanations using evidence about the relationship between an object's position and the energy it stores. The three main types in 7th grade are gravitational (based on height), elastic (based on stretching or compressing), and chemical (stored in molecular bonds).

Students connect these abstract forms to objects they see every day: a backpack on a high shelf, a stretched rubber band, and the food they eat for breakfast. Gravitational potential energy changes with height and mass, while elastic potential energy depends on how far an object is stretched or compressed from its resting position. These relationships set up students for understanding conservation of energy in the next topic.

Students build a much stronger understanding of potential energy when they can physically manipulate objects and measure changes rather than just reading about them. Active learning approaches that put materials in students' hands make the invisible concept of stored energy far more concrete.

Key Questions

1. Explain how the position of an object can determine its stored energy.
2. Compare and contrast gravitational potential energy with elastic potential energy.
3. Predict the amount of work an object can do based on its potential energy.

Learning Objectives

• Explain how an object's height and mass determine its gravitational potential energy.
• Compare and contrast the factors affecting gravitational potential energy and elastic potential energy.
• Predict the amount of work a stretched rubber band or a raised object can perform based on its stored potential energy.
• Identify examples of chemical potential energy in everyday substances and explain how it is released.

Before You Start

Introduction to Energy Forms

Why: Students need a basic understanding of energy as a concept and that it exists in different forms before exploring stored energy.

Mass and Weight

Why: Understanding mass is crucial for calculating gravitational potential energy, as it is directly proportional to the stored energy.

Key Vocabulary

Potential Energy	Stored energy an object possesses due to its position, shape, or chemical composition.
Gravitational Potential Energy	The energy stored in an object due to its vertical position above a reference point, dependent on mass and height.
Elastic Potential Energy	The energy stored in a flexible object when it is stretched or compressed from its resting position.
Chemical Potential Energy	The energy stored within the chemical bonds of molecules, released during chemical reactions.

Watch Out for These Misconceptions

Common Misconception

Potential energy only applies to objects held up high.

What to Teach Instead

Potential energy includes gravitational, elastic, and chemical forms. A stretched rubber band on a flat table has elastic potential energy without any height involved. Having students test multiple types at lab stations helps break this gravitational-only assumption.

Common Misconception

An object needs to be released or moving before it has energy.

What to Teach Instead

Energy can be stored in a stationary object based on its position or state. A book on a desk has gravitational potential energy right now. Physical demos where students feel the tension in a stretched spring help make this invisible energy tangible.

Active Learning Ideas

Stations Rotation: Potential Energy Stations

Students rotate through three stations: dropping balls from different heights to measure bounce height (gravitational), stretching rubber bands different distances to launch paper balls (elastic), and burning a food sample in a simple calorimeter to estimate chemical energy. At each station, students record data and identify what variable determines the amount of stored energy.

50 min·Small Groups

Think-Pair-Share: Height and Stored Energy

Show a slow-motion video of a diver from different platform heights. Students individually sketch a diagram showing where potential energy is greatest and where it converts to kinetic energy, then compare their reasoning with a partner before sharing out.

15 min·Pairs

Inquiry Circle: The Rubber Band Launcher

Groups stretch a rubber band to three different distances and launch a small projectile, measuring how far the projectile travels each time. They graph the relationship between stretch distance and launch distance to show how more stored elastic energy does more work.

40 min·Small Groups

Real-World Connections

• Engineers designing roller coasters utilize gravitational potential energy, calculating how height and track design will influence the speed and thrill of the ride.
• Athletes in sports like archery or gymnastics store elastic potential energy in bows or their bodies, releasing it to propel arrows or perform acrobatic feats.
• Food scientists and nutritionists analyze the chemical potential energy in different foods, helping to create balanced diets that provide the energy humans need for daily activities.

Assessment Ideas

Quick Check

Present students with images of various scenarios: a ball at the top of a hill, a compressed spring, a log of wood, and a charged battery. Ask them to identify the primary type of potential energy stored in each and briefly explain why.

Discussion Prompt

Pose the question: 'If you drop a ball from a certain height, what happens to its gravitational potential energy as it falls?' Guide students to discuss the transformation of potential energy into kinetic energy and how height affects the initial stored energy.

Exit Ticket

Students answer the following: 1. Write one sentence comparing gravitational and elastic potential energy. 2. Give one example of chemical potential energy and how it is released.

Frequently Asked Questions

What are the different types of potential energy in 7th grade science?

In 7th grade, students work with three main types: gravitational potential energy (based on height and mass), elastic potential energy (based on stretching or compression), and chemical potential energy (stored in bonds). Each type can be released to do work or convert to kinetic energy.

How does active learning help students understand potential energy?

Potential energy is invisible, which makes it hard to grasp from a diagram alone. When students physically stretch rubber bands, drop objects from measured heights, and track how far things launch, they build a direct sensory connection to what stored energy means. This hands-on approach makes the MS-PS3-1 standard much more accessible.

How do you calculate gravitational potential energy?

Gravitational potential energy equals mass times the acceleration due to gravity times height (PE = mgh). In 7th grade, students typically focus on the conceptual relationship: more mass and greater height both increase stored gravitational energy.

What is an everyday example of elastic potential energy?

A stretched rubber band, a compressed spring in a pen, a drawn bowstring, or a trampoline surface all store elastic potential energy. When released, this stored energy converts to kinetic energy and does work by moving an object.