Magic as an Introduction to Scientific Thinking

I love magic.  Being a scientist doesn’t take away from the amazement created by a well executed trick.  My father sent me a clip of Chris Angel doing a trick where he not cuts, but pulls a woman in half right on a park bench.  The trick is incredibly shocking, the people on the set are screaming in fear and surprise.  You can see they are visibly shaken.

I’m going to show this clip and then start a discussion.  First question – did he really pull this woman in half?  Obviously that did not happen, so what did?  The students are going to either work alone or in small groups and try to come up with a way to explain and possibly reproduce the effect.

What I hope to get from this exercise is a little critical thinking.  If the woman was not pulled apart, and Chris Angel doesn’t have real magical powers, then it must be a trick.  We don’t know how he does it, but we can make educated guesses and then experiment to attempt to reproduce the method.

Optics with Jello Lenses

How do you see light’s path through a lens?  We did this experiment at the DAMOP teacher’s workshop at Penn State last year.  Make Jello in a flat bottom pan, about 3/4″ deep.  Use half the water so the Jello is firmer than normal.  You’ll have to experiment with the color and tell me which works best, I haven’t done this on my own yet.

Obviously the Jello is made the day before.  Now cut the Jello into the shapes of the lenses.  You can make prisms, double concave, convex, whatever you like.  You can float the pan in warm water to release the lenses from the pan.  Don’t do it too long, just enough for the Jello to lift out undamaged.

Now shine a laser pointer through the Jello.  You will be able to see the path of the laser and follow as the light is bent by the lens.  Set up a series of lenses and have fun.  When you are done, you can eat the experiment.

Anyone Teaching Robotics?

I’ve been searching for a curriculum and some ideas for teaching robotics.  I’m looking to build a course that is half a year of robotics and half a year astronomy.

I haven’t found very much so far.  Some stuff at Carnegie Mellon and constant links to Lego products, but not much else.  I’m looking to make this an elective the following year and I need to start figuring out how I’m going to make this happen.

Some of you must either teach this course or have someone in your school who teaches this course.

I need some help please.

One Year!!!

Today is the 1-year anniversary of this blog and I get the feeling it has been rather successful.  I’m currently getting roughly 7,000 page views a month.  I never would have expected 78,000 page views to a physics teaching blog in a single year.  I guess I’m not the only one that needs help figuring out what to do each week.

Best of all, I’ve made some new friends around the world.  That’s just too cool.

Thanks for all the support and comments.  Live long and prosper.

Scott

Emergency Lesson Plans

I’m almost never out sick.  This is a good thing because my emergency lesson plans are, well, they kind of suck.  It’s motivation to come to work.  The few times I’m out, I either have the sub put on Mythbusters, or I email in a lesson based on our current work.

I would really like to have some better, stand alone emergency plans, but all I’ve come up with is Einstein’s Puzzle.  It’s a logic puzzle that takes quite a bit of thinking and time to solve.  I give extra credit for getting it right.  (Yeah, I’ll post it later, or email me if you think you’ll forget to come back.)

I need something else.  Maybe I’ll design some review worksheets of conversions or scientific notation, or maybe an SAT II section on Physics.  I’m going into my 4th year teaching these courses and that’s the best I’ve been able to do.

I need help.  Or an intervention.  What do you do?

Tell Me About Yourself – A Quick Poll

Just a quick poll to help me understand who is stopping by my blog.

This is so cool, thanks for participating.

Really Cool Lab Notebooks

I received an email from a rep from Bedford, Freeman, & Worth Publishing (http://www.bfwpub.com/highschool) with their latest textbooks and a lab notebook that has carbonless copies.  I was intrigued since I’ve not been happy with my use of notebooks (see my post on Pulley Lab).  I really like the idea of the students using lab notebooks, and I do more than enough experiments to make it worth keeping one, but carrying 100 of them home to grade … it just doesn’t happen.

To make my life easier, I’ve created a bunch of mini-labs where they get a handout, answer questions and hand it in by the next day.  This has worked well from a grading point of view, but the students haven’t had to keep a lab notebook anymore, and so I’ve lost the college-level work I’m aiming for.

I think these carbonless copy notebooks may be the answer.  We are going to try them next year.  The students will be required to purchase them at the school store.  They are not inexpensive, the cost to the school is between $9 and $11 each.

Anyone using these?

You can find the link for the publisher here:  http://www.haydenmcneilspecialtyproducts.com/products/physical-science.html

Introducing The Scientific Method – A New Idea

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.

Using Lateral Thinking Puzzles

If you don’t know what a lateral thinking puzzle is, google it.  These are great puzzles to make the kids think a little differently.  The kids make so many assumptions, I’m always struggling to find ways to open up their thinking process.

I had a period to kill with one of my classes, so I pulled out a few of these puzzles.  It’s real important to lay down the rules for the puzzles.  They need to take turns asking questions, they get into it, but I can’t answer questions when they talk over each other.  The questions have to be in a form that I can answer with yes or no.  Sometimes I answer with “doesn’t matter” or “I don’t know” and that irritates them because it wasn’t in the rules.  It was, I just didn’t tell them.

The idea is for them to start asking questions and realizing they assumed an incorrect body of information.  Here’s an example, it’s so common, I don’t think I’m ruining any great puzzle sharing it.

A body is discovered in a park in Chicago in the middle of summer.  It has a fractured skull and many other broken bones, but the cause of death was hypothermia.

The solution is usually in the form of a story that the kids need to work out through their questioning.  Here is the solution to the above puzzle:

A poor peasant from somewhere in Europe desperately wants to come to the United States.  Lacking money for airfare, he stows away in the landing gear compartment of a jet.  He dies of hypothermia in mid flight and falls out when the compartment opens as the plane makes it final approach.

Check out some online sources and books at the stores.  I have a couple of books, but I find most of the puzzles aren’t good enough to use in class.  I might highlight for or five puzzles from a small book of puzzles.  Tell me how they work out for you.

First Pass at Series & Parallel Circuits

This mini-lab worked out really well.  In fact, quite of few kids surprised me by getting into building circuits.  I know a lab goes well when nobody bails or gives up in frustration.

I introduced series and parallel circuits with three quick overheads.  I also taught them the schematic symbols for a battery, switch, and bulb.  I helped them out by drawing the schematic for the first problem.  The attached document is pretty much self-explanatory, but I would suggest you have the kids read the last couple questions before they start building.

I had the kids in groups of two.  Each group needed a 3v battery pack (2-D cells), two light bulbs in holders, two knife switches, and about 6 sets of alligator jumpers.  You could use pre-cut wires, I had the jumpers available.

series-and-parallel-switches

With the introduction to series and parallel circuits, the lab took the entire class period to complete.

Lemon or Lime Battery

It’s not about being politically correct.  Limes are cheaper than lemons.  A bag of 5 limes was $1, lemons were $2.  Since we were sticking metal in them and then throwing them away, frugality wins.  Besides, I have some leftovers that may become margaritas.

Now, I ran out of time and didn’t create a lab sheet, so I had to wing this a bit.  We did have a kit from Carolina that included electrodes of Fe, Cu, Al, and Zn.  I decided I would have less trouble if I did the cutting into the limes.  I used a plastic knife and cut two slits about 3/4″ apart, large enough for the electrodes to easily slip into the lime.

On the board I created a simple 4×4 matrix of the metals and had the students test each metal pair as electrodes.  I also had them test Fe-Fe, and Cu-Cu, etc.  That meant they had to share electrodes to get the similar pairs.  They found that only dissimilar metals created a voltage and the voltages were not all equal.  Cu-Zn created the largest, at around .9 volts.

Next, I had them pull out change from their pockets and try the coins as electrodes.  I also had some galvanized screws (zinc coating) for them to use.

Once they had a feel for what makes their battery work, I gave them each an LED for them to try to light up.  A single battery didn’t have enough voltage, so they had to partner up with another group and figure out (with some guidance in the form of a drawing on the board) how to wire the batteries in series.  With two, they could get a red LED to light up.  We had to turn out the lights to make it visible.  The green LEDs seem to require more power and didn’t light up with the same batteries.  They also wired three together and made the light even brighter.

Yes, I needed more organization.  Tomorrow we do series and parallel circuits using switches and light bulbs.  It’s fourth quarter and I feel like I’m out of energy myself.

Experiments with a van de Graaff Generator

I now feel qualified to put something up on this post.  We played for two whole days in my physical science class, and the kids still want more.  Another day in my three physics classes, and I’m battle ready.

I began by showing the balloon on the bald teacher’s head and sticking it to the wall.  Trust me, nothing gets them going more than a mostly bald teacher trying to rub a balloon on his hair. Amazingly, there were quite a few students that had never seen a balloon charged up and stuck to a wall.

We then went to the standard acrylic/fur type of static charge, explaining how the charges separate.  I caused paper and bits of styrofoam to jump from the charge.

The van de graaff generator is exactly like those static creating devices, but it just keeps making more and more static.  Here are a few ideas I have either done or picked up on the internet.  One important note; I got all of the kids up and involved.  Some of them were scared, but after the girls charged up their hair without pain, the chickens were shamed into bravery.

Before doing each of these demonstrations, I ask the students what they think will happen:

1.  I take a bunch of holes from a paper punch and put them on top of the dome.  Then I turn the machine on and the holes fly up into the air.  The dome and paper, all having the same charge, repel each other.  The paper holes spray up in a fountain of white dots.

2.  I tape strips of paper to the dome.  The paper stands up and stays standing until the dome is discharged.  This is a good precursor to the hair thing.  They don’t expect the paper to stay up in the air when the machine is off.

3.   I use the grounding electrode to make the sparks jump really far.  Let the generator run until you hear the ozone crackling.  Then you get a great big spark.  I use this to build some tension and fear of the generator because I’m asking for volunteers to do the hair thing.

4.  Making hair stand up.  The student needs to stand on a plastic milk crate or something to insulate them from the floor.  One student wanted to try this standing on the ground.  I think he had sweaty feet, he said (and we heard) the discharge going through his feet into the floor.  I wish I could tell you how to know what kind of hair works best.  Really long hair is too heavy, really short hair is too stiff.  Hair color doesn’t seem to matter, although dark is easier to see than blond.  For some reason, the hair of the black girls worked best.  I’d love to post the pictures, but posting pictures of student’s is a no-no, at least without written permission.

5. Fluorescent light bulb lights up.  It does not need to come into contact with the dome, the spark jumping to the glass with light up the bulb.  We found that placing the bulb about 1 inch from the dome gave the best results.  Stand on a piece of wood or you will feel the shocks in your toes.

6.  We made a chain starting with one person charged up.  He touched the next person, but held on.  Now they both charged up and continued to another person.  If the person getting shocked was sitting in one of our desk/chair units, he or she got a constant stream of shocks to the legs and back side.

7.  Water bottle on top produces lightening like show.  I’m going to tell you to be careful with this one.  It works pretty well at first, but the massive sparking in the bottle actually burned through the bottom of the plastic bottle.  Once they started leaking, they wouldn’t charge up.  I had to use a different bottle for each class.  More importantly, the bottle kept the charge.  Just holding the bottle and moving it around gave a constant stream of rather painful shocks.  At one point I was holding the grounding rod and the bottle.  I touched where the bottle was leaking through the bottom and I got an extremely nasty jolt across one arm to the other.  Be careful with this one.

8.  A balloon placed near the dome is first attracted, then when it touches the dome, the charge is conducted and it is repelled.  The charge leaks off and this repeats over and over again.  I used this to lead into Coulomb’s Law and the force due to the electric charge.  Again, you will want to stand on something to insulate you or you will have toe sparks.

Here are a few demonstrations that I haven’t yet tried:

• Mini pie tins stacked on top fly away one at a time – the pie tins I tried were too big.
• Soap bubbles are repelled as they get near the dome.

Any more?

Pulley Lab – Mechanical Advantage

I’ve been doing this lab for a number of years, but it needed a make-over.  I did that today, it’s beefed up a little and I added a data sheet.  I’ve gotten away from the lab notebooks because they are just too hard for me to collect and take home, and I never seem to be able to grade at school.  I’ve headed towards more of a “min-lab” format that I read about in The Physics Teacher a year or two ago.  This has greatly cut down on my grading, which allows me to do more lab and hands-on work, which gives me more to grade.  Somewhere in there we reach equilibrium.

This lab uses two double pulleys, some mason line, a ring stand and ring,  spring scales, a meter stick and a weight.  I like to use a 1 kg weight.  It’s heavy enough that they can feel the difference when the pulley helps out, but not so heavy that everything is falling over.  I found it helpful to have two or three different size strings.  The short string for the first three configurations is about a foot long.  They then switch to a second string that is four or five feet long.  I would suggest you play with the lab and then make up the appropriate length strings.   I like the pink mason line, it’s easy to see from across the room, so I can tell what’s going on at every work station.  It’s also easy to find when things are misplaced.

Here is the lab and data sheet:

pulley-lab-rev-c2

pulley-lab-data-sheet1

I would love suggestions and ideas to improve this lab.  I’m still not thrilled with the overall lab, but it’s the best I’ve been able to do so far.

Fun with Dry Ice

Long story short, we went to Penn State, visited the nuclear reactor, toured the school, ate lunch, and purchased two coolers full of ice cream.  It’s a 3+ hour ride home, so we also purchased dry ice for $0.75 per pound.

The next day, there was still quite a bit of dry ice left over, so I did this demo for each of my classes.  I put the dry ice in water and watched the “smoke” pour out.  I had another beaker with water and some dish soap.  Adding dry ice to that makes a huge pile of bubbles that are cloudy and evaporate on contact.

The best part was that the kids suddenly had a ton of questions.  They wanted to know what would happen if they inhaled the gas, if the water was safe after the dry ice was gone, and lots more.  Don’t forget to play, it’s a great way to learn.

Measuring the Coefficient of Friction

I developed this lab for my physical science classes, but I wish I had thought of it for my physics classes.  Since we do more with the coefficient of friction in physics, I will be upgrading and adding this lab to my course for next year.

In this lab, the students pull various objects across different surfaces.  The objects pulled were what I could get my hands on in a very short amount of time.  I had wooden blocks, plastic coated weights, steel weights, aluminum ringstand rings, and I asked the students to also use their sneakers.

They pulled these objects across a whole range of surfaces.  They used the top of the desk, the floor tiles, cardboard, plywood, tile board (white board), a rubber coated lab apron, cork board, and Styrofoam sheets.  I asked them to get creative and find objects and surfaces in the room.  I didn’t have sandpaper out, but many of them asked for it in their write-up.  The plan was to pick an object, pull it across as many surfaces as possible, then move on to another object.

They were surprised at the stickiness of the aluminum ring on the shop apron. I was too, it had a coefficient of friction greater than 0.5.

When I do this with my physics students, I will probably add a component where they have to predict the maximum angle of incline for an object on a surface before it starts slipping.  I like that.

Here’s my lab paper:  measuring-the-coefficient-of-friction1