Archive for January, 2009

Making Rock Candy

Take advantage of the process of crystallization to make candy!  You’ll create a super saturated solution of sugar and use it to grow your own homemade sugar candy crystals. (A super saturated solution is one that has as much sugar dissolved in the water as possible.  Note- if we didn’t heat the water, we’d wind up with only a saturated solution.)

Boil three cups of water in a large pot on the stove.  Add eight cups of sugar, one cup at a time, slowly stirring as you go.  The liquid should be thick and yellowish.  Turn off the heat and let it sit for four hours (or until the temperature is below 120 degrees F).  Pour the sugar water solution into clean glass jars and add a couple drops of food coloring (for colored crystals).  Tie a string to a skewer, resting the skewer horizontally across the jar mouth.  Let sit for a few weeks to a few months.

What kind of questions can you ask about this project? What happens when you vary the amount of water?  Sugar? Time? Seed or not to seed the stick?  Does it really matter how warm the environment is?  What if you don’t heat the solution to dissolve more?  Can  you color the crystals?  Why does the color stick (or not)? Does salt work instead of sugar? How about epsom salts? Does laundry detergent work, too?

The images below are sugar crystals, ammonia, and copper crystals.

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Make a buzzer from a cheap relay…

If you have a relay from Radio Shack (Part #275-206 or similar), you can quickly form it into a buzzer with a DC power source. Remove the plastic housing so the connections are exposed (and you can clearly see which terminal is connected where.

Connect one coil terminal to ground (black battery wire), the other coil terminal to a place that connects to the clicker when not powered (rest position).  Connect power (the red wire) to the clicker.

Can you find the spot where you get a nice zap when you touch it with your fingers? (Note – you may need more than 3V to make this work with your particular relay.  Try 9 or 12V.)

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Two Soda Cans Explain Why Airplanes Fly

Lay a row of naked straws parallel to each other on a smooth tabletop. Place two empty soda cans on the straws about an inch apart. Lower your nose to the cans and blow hard through the space between the two cans and *clink* they should roll toward each other and touch!

Why does this happen? When air moves, the pressure decreases. This creates a lower (relative to the surrounding air) air pressure pocket right between the cans. Recall that higher pressure pushes, and thus the cans clink together. Just remember – whenever there’s a difference in pressure, the higher pressure pushes.

What kinds of questions can you ask about this project?  For example: What types of cans work and don’t work?  How much air pressure you you really need – would a hair dryer be a better choice?

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Measuring the Speed of Light

So this is a more advanced project… and one that takes patience.  There is an easy way and a hard way to do this project.  I particularly like the hard way better, because there’s more observational science involved and less mathematics.  But let’s start with the easy way first.

Easy Method for Measuring the Speed of Light In a transparent tupperware, make a batch of clear gelatin (like jell-o) and let it harden.  Skimp on the water so the mixture is very firm.  When ready, take it out of the fridge and shine a laser beam through the side of the tupperware… you’ll see the beam ‘bend’.  Carefully measure the angles of incidence and refraction and use Snell’s law to back-calculate the speed of light.

For reference, the index of refraction for ice is 1.31; for water at 20 deg. C is 1.33; for diamond it’s 2.42; for plexiglass it’s 1.51.  For your measurement to be completely accurate, you’ll need to remove the tupperware and measure it for the gelatin.

…to be continued…

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Solar Storms and Crazy Compasses

Once upon a time, people noticed some of the rocks on the planet stuck to other rocks… and soon after floated a shard of metal in water and noticed that it pointed the same direction no matter how you rotated the cup.  We know today about the earth having a magnetic field that keeps the needle pointing in the same direction… at least, until a thunderstorm bolts through the area.  When this happens, the needle spins around and doesn’t settle on any one particular area… a problem if you’re a sailor at sea.

Other things can cause small pockets of changing magnetic fields on the earth, such as solar storms.  The sun burps and spits out high energy photons and other particles all the time, some of which make it to earth, but most of which harmlessly pass by.  The ones we notice, however, happen when a magnetic loop on the sun snaps and breaks free, causing high energy particles to zoom toward earth.  When this happens, we get the ‘aurorae’ at the poles and pockets of fluctuating magnetic fields that are detectable with a small homemade device called a magnetometer.

You’ll need one clear, plastic bottle (soda or large water bottle with the label removed), thin cotton thread, a small magnet, an index card, a tiny mirror or thin piece of mylar, one naked straw, glue, tape, scissors, yardstick or measuring tape, and a laser.  The basic idea is this:  using an amplifier (light shot over a distance), you can detect very small changes in the magnetic field using a magnet on a low-friction spring (the thread).

Attach the bar magnet onto the index card and glue the small mirror to the magnet.  Suspend the card from the bottle cap with a length of thin string (you can test out fishing line, single fibers from nylon rope, sewing thread, etc.) and stick the whole thing inside a plastic bottle.  (You can cut off the bottom of the bottle to use as a bell-jar.)

After the card settles down, it’s time to play with the experiment.  Shine your laser on the mirror at a wide angle, and you should see a dot on the wall.  Tape a piece of paper to the wall and carefully mark the position.  Over the course of a few hours, you will notice the dot “move”.  Mark the new locations with the time and date.  Make sure you’ve got a wide angle – there should be at least 90 degreed between the incoming and outgoing laser beam.

What kind of questions can you think of to ask about this project?

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Science Project using Lasers

I get a lot of questions about how to turn  “cool”  projects into a true science fair project, and lasers are one of the activities people really want to know about. So here are the basics:

The word “LASER” stands for Light Amplification by Stimulated Emission of Radiation. A laser is an optical light source that emits a concentrated beam of photons. Lasers are usually monochromatic – the light that shoots out is usually one wavelength and color, and is in a narrow beam.  By contrast, light from a regular incandescent light bulb covers the entire spectrum as well as scatters all over the room. (Which is good, because could you light up a room with a narrow beam of light?)  A laser controls the way energized atoms release photons.

Quick note about lasers: cheap key chain lasers (like from “dollar” or “thrift” stores) work just fine with these projects. Do not use green lasers – they can cause permanent eye damage.

For starters, take your laser and zip around the house before bedtime finding cool things to shoot your laser at (or through).  Try clear bottles filled with different liquids (soap, milky water, vinegar, rubbing alcohol etc.).  Try lamps, (dark) clear light bulbs, windows, cut acrylic or crystal pieces, CDs, eyeglasses, saran wrap, colored cellophane, feathers, aluminum foil, and the mirrors in the bathroom  Once you find a cool effect, start your scientific investigation by honing in on a question you want answered – something that came up when you were playing with your laser.

One question that pops out naturally when we teach the Lasers class for kids is: “Does the beam pass through the window or reflect back?”  And when looking up the answer, we found that it did both (during our research step), which triggered another question about how lasers interacted with mirrors, from which we formulated the question and later our hypothesis…

Hopefully this gives you ideas and gets you started!

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Awesome Science Projects Now LIVE!

Okay – it’s here! You can now check out the latest awesome Science Fair Projects at this link:

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