Physics & Physical Science Demos, Labs, & Projects for High School Teachers

Introducing the Scientific Method

Posted on: August 24, 2008

I just got this idea in the shower this morning.  Here’s the basic lesson:

  • Divide the class into groups.  Give each group a complete but non-working flashlight.
  • Ask them to look at the flashlight, but not take it apart.  They are to predict why it isn’t working and propose a solution.  They need to come up with a test to show their prediction is correct.
  • Once documented, they can take the flashlight apart and attempt repairs.
  • Each time they reassemble the flashlight and it doesn’t work, they need to stop and come up with a new written plan.
  • The group must document each step as they try to determine what is wrong with their flashlight.

Since these are very simple devices, they can be set up as follows:

  • One or more dead batteries
  • Tape over battery terminal
  • Batteries installed incorrectly (positives together)
  • Dead bulb (see update below)
  • Switch or broken circuit in flashlight

I would probably set each flashlight up with at least two failures so that the exercise is not over in a minute.  For instance, if I installed the batteries incorrectly, I would also make sure that one of them is dead.

There are two ways they can problem solve.  They can share parts with other groups to make the flashlights work or there can be a pile of batteries, bulbs, and bodies to use.  I’m also not sure if I want to have meters available.  I may have them available but only if someone thinks to ask for one.

I’m not sure how I want to conclude the lesson.  I would probably go into a class discussion of how they developed their plan and made sure the test did what it was supposed to do.

This looks like it’s going to be fun to watch.  I need ideas for wrapping it up.

Update… We did this lab today (9/11/08)

I wrote a lab procedure for this:  Flashlight Lab.  There were only a couple little changes.  I used clear plastic between the bulb and the bulb holder.  It made the bulb look perfectly normal, but it formed a nice invisible insulator that served to fool them for quite a while.  For the switch, I put clear tape over the contact from the switch.  Some of them found that though, it was hard to disguise and it stood out.

I didn’t let the students share information between groups.  I told them I didn’t have spare batteries, so they had to come up with a way to test them.  If they were clever enough to ask, I let them use a multimeter or spare parts from other flashlights.  I didn’t show them how to use the meter, but I did set it up properly.  They figured it out on their own, which impressed me.  I was hoping they would think of swapping parts with their neighbor, but they didn’t.

This lesson served two purposes: it demonstrated the scientific method since they had to cycle through the hypothesis-test-results process several times until they figured out everything that was wrong.  The lab also served as a lesson in following directions.  One of the groups did exactly what they were to told not to do and took everything apart and got it working in a minute.  They had no documentation, hypothesis, or controls.  They couldn’t tell me the three problems with their flashlight, their experiment was worthless.  I told them that they failed the lab and they also showed me I can’t trust them with chemicals and fire in the lab if I can’t trust them with a flashlight.  Hopefully that made an impression.

This experiment was done in my 12th grade Physical Science class and the overall response was positive.  The kids liked the hands-on challenge and were impressed at how devious I was at sabotaging the flashlight.  I think this is definitely worth doing.  Let me know what you change and improve.


7 Responses to "Introducing the Scientific Method"

I like your scientific method and will probably use it in the first few weeks. Another good opening lab is building a pinwheel….You’d be surprised how long it takes the kids to figure out the key to a successful pinwheel.
Have a great year and thanks for the lab

This is a great idea. I am interested to know how it worked with you.

For my Earth/Physical Science class I am going to use this activity in the first week or so. I think I’ll present it as a problem solving activity. To start the activity I will have them write the steps they take to figure out what is wrong on a piece of white paper. A guide sheet could help with sections for Trial 1, Trial 2….etc.

I will conclude the activity by giving them strips of paper each with a different step of the scienctific method. Then they will have to cut out the steps they wrote down and pair each up with the step of the scientific method they think it goes with. At the end I can give them the correct order for the scientific method and we can discuss any differneces they have in their own list as well as how we all use the scientific method in some form every day. This will allow me to talk about the importance of each step in the scientific method. Anyway, thanks for the great idea!

I did your activity this morning with my nine year old for homeschool. She loved it. I needed something simple to illustrate the scientific method and this was just the ticket. I made the flashlight non-functional in four different ways in about 30 seconds (no complicated lab prep!). It had her and her dad stumped for about 10 minutes. Easy, impactful lab. Thanks for the great idea!

Tried this lab on the first day of class and it was a lot of fun and a good way to get them thinking in a scientific way. Another good project we did was to play Mastermind. You know that game with the little colored pegs? Also surprisingly illustrative of the scientific method. Got the idea from Natalie Angier’s book “The Cannon” which has been really, really good so far, I highly recommend it.

I’m not surprised that they didn’t ask their neighbors for parts since you told them that they weren’t allowed to share information with other groups.

This is something that I’m going to put on my list of things to try next year though 🙂 Hmmm… it’s probably not too late to do it this year.

Thanks so much. I am planning on trying this in my university intro to chem class this spring. It looks like a great way to introduce the concept in a way that they can wrap their heads around.

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