Students explore machines and how simple and complex machines can allow us do work with less force or effort, through a selection of non-fiction texts and hands-on engineering projects.



Unit 7

3rd Grade

This unit has been archived. To view our updated curriculum, visit our 3rd Grade English Language Arts course.

Unit Summary

In this science unit, students explore machines and how simple and complex machines help us do work with less force, or effort. In the first part of the unit, students explore and learn about the seven traditional simple machines and how they work. They then explore how simple machines can be combined to form complex machines that are capable of doing many repetitive, difficult, complicated, or dangerous tasks. After learning about different simple and complex machines, students will participate in numerous hands-on engineering projects in order to deepen their understanding of machines. Students will be presented with different design problems with particular constraints and criteria. Students will then be challenged to come up with multiple solutions, evaluate if the solutions did or did not work, and then redesign based on observations and feedback. It is our hope that this unit, in conjunction with others in the sequence, will help students begin to realize that if they feel empowered to do so they can use simple machines and other resources to come up with solutions to problems in the world around them. 

For readers, this unit serves as the culminating unit of the year. The main focus of this unit is grappling with and exploring hands-on engineering projects; therefore, there are not as many reading days in the unit. On reading days, students will focus on using diagrams, illustrations, and text to explain the connections between scientific processes. If there are other spiraling reading strategies that students need support with, they should be identified and spiraled into the first part of the unit. Because the unit is predominately projects, rubrics should be created to score student understanding, participation, and speaking and listening over the course of the unit. Because the unit is more project- and exploration-based, there is not a traditional assessment at the end of the unit. Instead, student designs and projects should be scored on the rubric.

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Texts and Materials

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Core Materials

Unit Prep

Intellectual Prep

Build Background Knowledge

  • Research and learn about different types of simple machines. Brainstorm common examples of simple machines in the world around us. 
  • Research and learn about different types of complex machines. Brainstorm common examples of complex machines in the world around us. 
  • Research and learn about different playground equipment and the different ways simple machines are used in playground structures. 
  • Research and learn about how tunnels are built and why. 
  • Research and learn about how wrecking balls are used and why. 

Internalize the Text and Standards

  • Read all unit texts and notice evidence of unit priority standards and essential questions. 
  • Read and internalize unit science standards. 
    • What do students need to understand in order to show mastery of the science standards? 
    • Are there any clarifications in the standards? 
    • Why is mastery of the standards important for students? 
  • Plan lab/activity days that support science standards and deepening understanding of the content. Order materials. 
  • Create project rubric to guide student participation and exploration during project days. This rubric will be used to score students’ final projects. 
  • Create a visual to represent the different simple machines and common examples. Consider using the chart on pp. 19–20 of Simple and Complex Machines. 

Essential Questions

  • How do simple and complex machines make our lives easier? 
  • How can simple and complex machines help solve a design problem?

Writing Focus Areas

Informational Writing Focus Areas

  • Selects the most relevant text-based details and examples to support the claim 
  • Includes a variety of text-based evidence to support each reason (facts, examples, quotations, micros-stories, information) 
  • Uses words and phrases to connect different parts of the pieces together 
  • Provides an introduction to the claim
  • Provides a conclusion to the claim
  • Writes two or three sentences explaining each text-based reason
  • Makes a correct claim that connects to the topic and shows understanding of the text
  • Refers to more than one text-based detail from the text
  • Uses paragraphs to group ideas and evidence
  • Uses different paragraph structure depending on details and evidence 
  • Uses paragraphs with topic sentences, details, and conclusion 
  • Flexibly decides when to write a one-paragraph answer versus a multi-paragraph answer
  • Uses domain-specific vocabulary

This is the culminating unit of the year; therefore, the main goal is ensuring that all students are scoring a 3 or 4 on the rubric. In order to ensure that all students are scoring a 3 or a 4, plan targeted whole-class and small-group mini-lessons to remediate student areas for growth.


Literary Terms

design problem, constraints, criteria 


work, machine, force, inclined plane, ramp, wedge, screw, lever, fulcrum, wheel, axle, friction, pulley, gear, complex machines, tunnel, crane, wrecking ball, gravity, pendulum

Content Knowledge and Connections

  • Explain that a machine is a device that uses energy to do work. 
  • Explain that work is done whenever an object is moved over a distance. 
  • Identify that an inclined plane is a surface with a slope, or incline. Ramps are the most common inclined plane. 
  • Identify that a wedge is two inclined planes that meet. A wedge is used to help push things apart. 
  • Identify that a screw is an inclined plane wrapped around a rod with thread on the outside. Screws are most often used to hold two things together. 
  • Identify that a lever is a machine that lifts heavy things. A lever consists of a board or bar that rests on a turning point called a fulcrum. 
  • Identify that a wheel and axle are used to reduce friction and make it easier to move something. 
  • Identify that a gear is used to transfer motion or force from one place to another. It looks like a wheel with teeth. 
  • Identify that a pulley is used to lift heavy objects. 
  • Explain that a complex machine is made up of more than one simple machine.

Supporting All Students

In order to ensure that all students are able to access the texts and tasks in this unit, it is incredibly important to intellectually prepare to teach the unit prior to launching the unit. Use the intellectual preparation protocol and the Unit Launch to determine which support students will need. To learn more, visit the Supporting all Students teacher tool.

Lesson Map

Common Core Standards

Core Standards

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Unit 4

Exploring Ancient Civilizations: Rome