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Design and Build the Solution

Students must come up with a way to measure the change their invention will make. Measurement is the key to good science and good engineering. Just saying that our treatment made a difference is no good. We have to present evidence to ourselves and to others that the change occurred. Caution students to plan out their time carefully. “Backmap” the time: What is the date of the science fair? How long will it take you to write up the report and make the project display? Subtract that time from the date of the science fair. That’s how long you have to put your plan into action.


  • Use a spring scale to measure how much effort it takes to lift the backpack. Measure how much effort it took to pull the backpack on the wheels I will add.
  • Count the number of barks per minute the dog makes before I apply the negative feedback and after.
  • Read a sign from a distance of 10 meters away. Use the mirror invention to read the same sign from around a corner that is the same distance away.
  • Use different types of material to make an insulation sleeve for my drink box. Measure with a thermometer how the temperature changes over an hour, taking the temperature every five minutes.
  • Build a model in a large box made of wall board and use a sound meter program on my laptop computer to measure the decibels of sound that are reflected off the walls before and after I add a cloth hanging.
  • Count the number of pieces of recyclable paper in the trash can in our grade level classes. Place reminder signs on the trash cans in each classroom in our grade level. Then count the number of pieces of recyclable paper that are in after the signs are up.

Validate the design

Before presenting the project for your approval, ask students to answer these questions for themselves.

  • Is it safe to do?
  • If the change I propose affects others, can I get permission to do it?
  • What materials do I need and can I get them?
  • Do I have enough time to build and test my idea as well as to write it up?
  • If it involves living things, will they be safe?

Approve the project

Use the project Planning and Approval Sheet [link] to make sure students have good invention ideas that they can accomplish

Build the solution

This takes the most time, how much depends on the project, but students should know that they will need to leave themselves time to write up the results and prepare the presentation.