Scratch My Back

Children's Engineering Activity
(Grades K - 2)


This lesson is based on the book Big Smelly Bear by Britta Teckentrup. In the book, a big, smelly bear has an itch in the middle of his back and can't scratch it. Nothing the bear tries works. Using the Engineering Design Process, children will design, build, and test a backscratcher for themselves.

The activity, Invent a Backscratcher from Everyday Materials developed by Worcestor Polytechnic Institute, will be used as the basis for this lesson with modifications as shown below.


 Students will be able to:

  • Brainstorm several ideas for a backscratcher
  • Predict which materials will make the best device
  • Use prior and new knowledge to design the device
  • Compare the suitability of different designs
  • Describe in simple terms what an engineer does


 One hour for introduction to what engineers do; reading of story; designing, building and testing solution.




  • Ask children if anyone wants to be an engineer when they grow up. Ask if anyone knows what an engineer does. Explain that engineers design things to help people. And they figure out how to solve problems.
  • Read first half of Big Smelly Bear to children. Introduce the problem: The bear has an itch on his back that he can't scratch.


  • Stand up and pretend you have an itch in the middle of your back. Try to scratch it.
  • How could the bear's problem be solved?
  • What type of device could an engineer design and build that would help the somone scratch his/her back?
  • How will you know if it works?

Design and Construct

  • Provide constraints:
    • Work individually or in small groups of 2
    • Use only the materials provided
    • Design and build something to scratch your back
  • Students work to plan their ideas by sketching design first
  • Student build their devices

Evaluation of Designs

  • To test designs, have students swap backscratchers with another student or group and test out on themselves
  • The backscratchers must reach the middle of their backs, be easy to use and not fall apart
  • If time allows have the students work on improving their designs


  • Re-assemble children and ask a few students to describe their solutions – what worked and what didn't work. What would they do differently next time?
  • Finish reading Big Smelly Bear to children to see how the bear's problem was solved.

Photo Examples

Implementation in a Kindergarten class. Click for larger view.



Next Generation Science Standards: K-2 Engineering Design

ETS1-1 Ask questions, make observations, and gather information about a situation people want to change to define a simple problem that can be solved through the development of a new or improved object or tool.
K-2-ETS1-2 Develop a simple sketch, drawing, or physical model to illustrate how the shape of an object helps it function as needed to solve a given problem.

ITEA Standards for Technological Literacy

Standard 8: Students will develop an understanding of the attributes of design.
Standard 9:  Students will develop an understanding of engineering design.
Standard 11: Students will develop the ability to apply the design process

New Jersey 2009 Core Curriculum Content Standards

Standard 8.2 Technology Education, Engineering, and Design: All students will develop an understanding of the nature and impact of technology, engineering, technological design, and the designed world, as they relate to the individual, global society, and the environment. 

National Science Standards

Standard 6.5 Science and Technology: Abilities of technological design


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Center for Innovation in Engineering and Science Education (CIESE) All Rights Reserved.