Posts Tagged ‘scientific method’
I’ve been listening to Carl Sagan’s A Demon Haunted World on tape in the car and I’m awash with new ideas.
Next year, as part of the introduction to the scientific method, I need to draw a line on the board. On the left, I will write “Gullible,” on the right, “Skeptical.” If someone is totally gullible, they would believe that a cat matures into a dog. It seems silly, but the idea is that a totally gullible person takes any statement as fact without question. For a totally skeptical person, they would doubt you on absolutely everything you say and do. The total skeptic is so annoying that nobody wants to converse with him. Both extremes are no good, our job is to find a happy spot somewhere to the right.
Next, let’s talk about ESP. Is it real? Do you know anyone with ESP? If we were gullible, how would we answer to the claims of a person with ESP? What if we were skeptical? Let’s accept the claim that ESP might exist. How can we test it?
At this point, I want to break the students into groups. Their job is to come up with an experiment to test some form of ESP. They will need to write up their proposed experiment and then perform it the next day in class. They will then write up their results and submit their report to peer review by their classmates.
Wouldn’t it be cool if they could decide good experiments from bad through the process of peer review. I can’t wait to try this in September.
(This was submitted by Duane, a High School teacher in Georgia. Thank you Duane.)
One fun “observation vs. conclusion / assumption” demo that I love came from Flinn Scientific’s “A Demo A Day” for Chemistry. I call it the “Potato Candle”.
Cut a cylindrical core (apple corers work well) from a potato – rinse it in lemon juice to preserve the near-white color of the cut potato – then cut a cross in one end. Insert an almond sliver (available at any grocer in the baking goods aisle) into the sliver. Your “candle” is now ready for the discussion / demo.
Inform your students that they are to practice their powers of observation, and make as many observations about what they are about to see in a limited time frame. Turning the lights down or out aids in their “mis-observations.”
Light the almond sliver with a match – it will catch readily, and burn for about 2 minutes – so don’t give them much longer than 60 seconds to make their observations. Blow out the almond before it burns out, turn on the lights, and start taking notes on the board as to the observations the students made of the “candle.”
At some point, particularly effective after someone makes the observation that the “candle” is made of wax, note that that’s an interesting observation, calmly bite the potato candle in half, chew and swallow. Your students will be aghast for a moment, wonder if you’re as crazy as that seems, and it leads into a lively discussion on the differences between observations, conclusions, and assumptions based on previous experiences.
Hope you like it!
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.
I do this demonstration on the first day of school to get the students attention. After talking about the syllabus, what is physics, making them think, etc, I ask them which falls faster, a heavy object or a light object? I get the discussion going and everybody into it, then I jump up on my demonstration table, take off my shoe and ask which will hit the ground first, the pen in my hand or my shoe, which is now in my other hand. I drop them several times so that everybody sees they hit the ground at the same time.
I can’t tell you how many kids have told me they went home and did the same experiment. Sure it would work standing on the ground, but the act of climbing up on the table shakes them up and shows them this is going to be a different kind of class.
The popular show Mythbusters is a terrific example of the application of the scientific method. Early in the school year I introduce the scientific method. I then hand my class a worksheet that they fill in as they watch one of the episodes I have on DVD. They have to identify the hypothesis, controls, variables, experimental steps, and conclusion. mythbusters-and-the-scientific-method
Next, the student choose to work as an individual or in a small group (2 or 3) and they work on coming up with a myth they are going to bust. Now, you and I know this is just a mini-science fair project, but they don’t see it that way. My students were just telling me that this was their favorite project of the year. Good thing I didn’t call it a science fair project. Anyway, I let them do whatever they want so long as they are doing good science and they are not doing something dangerous. When there were a few that were dangerous, I discussed the project with their parents to make sure they were aware of what their kids were doing.
I teach in Philadelphia at a Charter School and the students come from all over the city. It is very challenging for many of them to work together outside of school, so I have to allocate class time for them to do their project. I think I give them 4 days over a period of 2 weeks to experiment, work on their poster, etc. I’ve attached the guidelines and worksheet I use for them to document their project. I make sure they have thought through the controls and variables before they begin any experiments. mythbusters-project-guidelines and mythbusters-worksheet
The grading rubric needs a rework, but I included it as a starting point. mythbuster-rubric
I have the students do the project on regular poster board. I do this early in the year and then hang the posters on my wall as they are completed. They like looking at each other’s ideas and projects, and they like picking them apart, explaining how they would do the experiment differently.