Tuesday, December 29, 2009

What is the Large Hadron Collider good for?

An essay in the New York Times by physicist and reporter Dennis Overbye. (Large Hadron Collider image: NYT)

Saturday, December 26, 2009

Act Now to Own Your Own Higgs Boson

There are 6 days left in an eBay auction for the "God Particle." This won't last long!

Here are the specs:

Mass: 114.4 GeV/c2 (just about none - or all)
Spin: 0
Field: Non-zero
Antiparticle: Self
CP violation: None (even)
Colour: Possibly
Size available: Small (fits all)
Optional extras: Large Hadron Collider, W and Z bosons (available in packs of 2,800,000)
Delivery: In envelope with CERTIFICATE OF AUTHENTICITY. (For a small extra charge we can secure your Higgs boson in a small lump of Blu-Tac and jam it in a matchbox. Please declare if you'd prefer that option.)
(Thanks to John Baichtal, via Twitter!)

Friday, December 18, 2009

Mass Lab: Conservation and Chemical Reactions

Not all the labs we did using the teacher resources from Einstein's Big Idea worked the way we hoped. One problem was my kitchen scale -- although it had lots of little numbers, it really wasn't sensitive enough to measure anything within the accuracy of its scale. (I'll post about the outcome of those labs another time.)

This lab, which comes from the Messing with Mass activity, also required a scale. So instead, I tried a technique from The Joy of Chemistry. We made up two identical bags of materials (see below) and hung them from a wire coat hanger set up as a balance. Then we mixed the contents of one bag while leaving the other untouched. The balance did not tip, theoretically showing that the mass remained the same even as the materials underwent a change of state from solid and liquid to gas. However -- like our insensitive scale -- it could just have been that the balance we set up wasn't very accurate. But basically the lab illustrated, if not demonstrated, what conservation of mass looks like. Here's what we did:

  • citric acid
  • baking soda
  • quart freezer bag
  • film canister, filled with water
  • wire coat hanger
  • rod for hanging
  • clips for hanging bag
  • measuring spoons
  1. Examine the two chemicals involved. (Ours came in packets left over from a root beer making kit. Although the original instructions warns students not to taste, if they're from your kitchen they're perfectly safe.)
  2. Measure out 1 teaspoon of citric acid into each bag. (We found the original 1/4 teaspoon too little to see much reaction.)
  3. Add 1 teaspoon of baking soda to the bags.
  4. Fill the film canisters with water and close the lids. Dry off the outside if needed and place 1 canister in each bag. Seal the bags tightly, squeezing out as much air as possible.
  5. Set up the rod so that the hanger can be hung from it. (We laid it across two tables.)
  6. Use the clips to attach the bags to the hanger as shown.
  7. Place the hanger on the rod, positioning the bags so that they are balanced. Use tape to hold them in place. (We didn't, and the bags did slide around.)
  8. Keeping the bag sealed, carefully open the film canister in one of the bags and pour the water out. You might want to leave the lid loose to make it easier to open.
  9. The chemicals and the water will react and produce a gas (carbon dioxide). The two bags should stay in balance.

Mass is the amount of matter an object contains -- as opposed to weight, which is a measurement of the force of gravity acting on it. As we saw in the documentary, Antoine-Laurent Lavoisier was the first to demonstrate that mass is conserved in a chemical reaction. Lavoisier made careful measurements of changes including water to steam in the late 1700s, aided by his wife, Marie Anne. Mass is always conserved in a chemical reaction in a closed system (except for an extremely small amount which is lost or gained in the form of light and/or heat energy).

We know a chemical reaction has taken place in the bag where the water was opened because the matter changed state, and because there was a temperature change. As the baking soda and citric acid combined, energy was absorbed producing an endothermic reaction. That means the bag got colder.

Thursday, December 17, 2009

Energy Labs: Battery-Powered Experiments

Continuing on with the description of the labs we did in conjunction with the PBS NOVA video Einstein's Big Idea, here are our adaptations of the directions for two activities using batteries:

Make An Electromagnet

  • insulated copper wire
  • rubber band
  • "D" battery
  • 2 large nails
  • small paper clips
  • wire stripper (or scissors)

  1. Cut a piece of wire about 40 cm long.
  2. Use a wire stripper (or scissors, carefully) to remove about 1 cm of insulation from the ends of the wire.
  3. Using the center of the wire, coil the wire around one nail, leaving about the same amount of wire on either side.
  4. Wrap the rubber band around the ends of the battery to hold the the wire in place.
  5. Connect the wires to the battery to create an electromagnet. Try to pick up paper clips and the other nail. Only keep the battery connected to the wires for 30 seconds.
  6. Touch the head of the nail after the circuit has been connected for 30 seconds to feel how the electrical current is making the metal heat up.
Explanation: The point of this station is that the magnetic field can do work. It can lift objects as the energy of the field is transferred to the paper clips. Since the strength of the nail's magnetic field is proportional to the number of coils of wire around the nail, we also experimented with different lengths of wire and numbers of coils.

Electrical to Heat Energy

  • batteries (we used pre-made "battery packs" with 4 AAs held together with tape and rubber bands and connected + to - with wires)
  • small lightbulb (we used one from an electrical set which came with wires)
  • compass
  1. Connect the lightbulb to the batteries using the wires. 
  2. Leave it lit for 15 seconds and feel the bulb heat up. 
  3. Using the compass, see if you can detect the magnetic field generated by the electrical energy traveling through the wire.
Explanation: The light bulb demonstrates how electrical energy can be converted to light and heat energy. Most of the light bulb's energy is given off as heat. The electrical energy is also the result of a transformation, from chemical energy (in the battery). As we saw in the documentary, Michael Faraday, a self-taught scientist in 19th century England, was the first to propose that the compass was being affected by invisible lines of force flowing around the wire.

Wednesday, December 16, 2009

Richard Wiseman's Top 10 Quirky Science Tricks for Christmas Parties

These "stunts" aren't just great for parties, they're also perfect quick and easy science demonstrations for kids. They come from the Quirkology YouTube channel created by Prof. Richard Wiseman from the University of Hertfordshire (UK). For more quirky science visit Wiseman's blog -- but be aware the blog has some not-safe-for-the-classroom informality.

Thanks to a whole bunch of people on Twitter.

Monday, December 14, 2009

Energy Labs: Mechanical and Heat Energy Lab

The Einstein's Big Idea teaching guide activities included a lab to demonstrate the conversion of mechanical energy to heat energy. It involved stirring cups of glycerin to raise the temperature a "few tenths of a degree." Since I doubted (a) that we had a thermometer which could measure such a small change accurately and (b) that anyone would be impressed by this, I went looking for a different lab we could do to demonstrate this phenomena. We did two labs, quoted below, from Arbor Scientific's CoolStuff newsletter. Both were simple, dramatic, and worked as described. They were part of a larger lesson on thermodynamics. I hope to do more of the lab another time!

Heating up a Hanger

The conversion of mechanical energy into heat may be dramatically demonstrated by simply bending a coat hanger. First cut a 30-cm length of coat hanger with wire cutters. Grab the ends of the wire in each hand and rapidly bend it back and forth several times. Now touch the point on the wire where the bending occurred. (Caution! The coat hanger can sometimes get surprisingly hot, so only touch the hot spot briefly.)

Stretching Exercise

Place a rubber band loosely looped over the index fingers in contact with skin just above your upper lip. Now quickly stretch the rubber band. What do you experience? Now let the rubber band relax quickly. What do you feel now?

When the rubber band is stretched quickly, work is done on it, causing its internal energy to rise. This rise reveals itself as a small increase in temperature. When the rubber band is allowed to quickly contract, it performs work and suffers a reduction in internal energy which produces a cooling sensation.

Wednesday, December 9, 2009

Energy Labs: Electrical Fields and Magnetic Fields

As mentioned previously, the companion website to the PBS show Einstein's Big Idea includes activities related to the three parts of Einstein's equation E=mc2: energy, mass and velocity. We worked our way through them, substituting and adjusting where necessary. Not all of them were as successful or illuminating as we hoped, but they were quick and easy to do and got us started on physics labs. The instructions below include the adaptations we made to the instructions from the PBS teachers' material.

The energy lab consists of seven activities, which they suggest you set up at different stations. We did these over the course of a few days. On day one, we did the electrical and magnetic field activities. Here is what the teacher's guide calls its "learning objectives:"
Students will be able to:
  • explain what the E in E = mc2 represents.
  • name different kinds of energy.
  • show examples of how one kind of energy can be converted into another kind of energy.
  • describe how a field can exert a force and cause an object to move.
Electrical Field Lab

• one plastic spoon for each person
• 10 cm x 10 cm piece of wool or fur (we used a woolen scarf, and the hair on our heads!)
• pieces of plastic foam cup, crumbled into bits
• pieces of paper, about 0.5 cm by 1 cm each

1. Rub a plastic spoon with a piece of wool, some fur, or your hair. Place the spoon next to a small piece of paper. Can you make the piece of paper stand on edge and move back and forth?

2. Try to pick up several pieces of paper at the same time by touching the spoon to one edge of each.

3. Recharge the spoon by rubbing it again. Try to drop a small bit of plastic foam into the spoon from different heights above it.

Explanation: Students are examining the effects of an electric field produced by rubbing a plastic spoon on fur. Once the spoon is charged (negatively), it will attract an uncharged object like a piece of paper through electrostatic induction. The large negative charge on the spoon repels the electrons in the piece of paper and leaves the side of the paper near the spoon slightly positive. (Positive charges-in the nucleus of each atom within the paper-hardly move at all.) Then, the negative spoon attracts the now positive side of the paper. If students are careful in their approach to the paper, they should be able to make it "dance."

Plastic foam becomes instantly negatively charged when in contact with another negatively charged object. The bits of plastic foam acquire a negative charge when they touch the spoon and are repelled immediately. It is impossible to catch a piece of plastic foam, no matter how close to the spoon it is held. If students claim they can, have them recharge their spoons. Watch the pieces of foam cup go veering away from the spoon in this video:

Magnetic Field

• several types of magnets, including bar or horseshoe
• small shallow cardboard box
• piece of white paper (cut to fit box)
• small container of iron filings (I found one in an old chemistry set.)

1. If the box is not white inside, fit a white piece of paper into the bottom of the box.

2. Center one or more of the magnets under the box.

3. Sprinkle iron filings into the box over the magnet. Lines of magnetic force should begin to become visible. (See photo at top.)

Explanation: Students should realize that the field from the magnet is exerting a force on the iron particles. The filings will align with the north and south field lines. Watch as the lines form in the video below:

Saturday, December 5, 2009

Physics2000 - Relativity First!

Continuing my investigation into the idea of teaching modern physics before classical, I've come across a website called Physics2000. Here's a description:
Physics2000 is a college level introductory physics course that begins with special relativity, ends with quantum mechanics, and in-between covers the usual topics with a 20th century focus. This approach eliminates the great divide between classical and modern physics.


Introducing Einstein’s special relativity in Chapter 1 means that you cannot rely on the usual mathematical techniques because no mathematics has been discussed yet. You have no choice but to focus on the physical ideas like the behavior of clocks and measurements of distance. The result is that you remove the mathematical fear factor usually associated with the subject. The only mathematics you need is the Pythagorean theorem.
According to the website, the Physics2000 course can be ordered on CD, including the text (there are calculus and non-calculus versions) and videos, for $10. Several of the chapters are available to preview online. It looks worth checking out.

NOTE: There is also an old, apparently unrelated website from the University of Colorado called Physics 2000. It contains online interactives on modern physics from a conceptual viewpoint.