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This fresh collection of more than 20 science projectsfrom hydrogen fuel cells to computer-controlled radio transmittersis perfect for the tireless tinkerer. Innovative activities include taking detailed plant cell photographs through a microscope using a disposable camera; building a rocket engine out of aluminum foil, paper clips, and kitchen matches; and constructing a geodesic dome out of gumdrops and barbecue skewers. Organized by scientific topic, each chapter includes explanations of the physics, chemistry, biology, or mathematics behind the projects. Most of the devices can be built using common household products or components available at hardware or electronic stores, and each experiment contains illustrated step-by-step instructions with photographs and diagrams that make construction easy. No workbench warrior, science teacher, or grown-up geek should be without this idea-filled resource.
|Publisher:||Chicago Review Press, Incorporated|
|Product dimensions:||7.00(w) x 10.00(h) x 0.38(d)|
|Age Range:||12 - 17 Years|
About the Author
Simon Quellen Field is the author of Gonzo Gizmos and creator of the popular website www.scitoys.com.
Read an Excerpt
Return of Gonzo Gizmos
More Projects & Devices to Channel Your Inner Geek
By Simon Quellen Field
Chicago Review Press IncorporatedCopyright © 2006 Simon Quellen Field
All rights reserved.
Hydrogen Fuel Cell
A fuel cell is a device that converts a fuel such as hydrogen, alcohol, gasoline, or methane directly into electricity. A hydrogen fuel cell produces electricity without any pollution; pure water is the only by-product.
Hydrogen fuel cells are used in spacecraft and other high-tech applications that need a clean, efficient power source.
You can make a hydrogen fuel cell in your kitchen in about 10 minutes, and demonstrate how hydrogen and oxygen can combine to produce clean electrical power.
* 1 foot of platinum-coated nickel wire or pure platinum wire (available from science supply stores, or at www.scitoys.com)
* Popsicle stick or similar small piece of wood or plastic
* 9-volt battery clip
* 9-volt battery
* Transparent sticky tape
* Glass of water
* Volt meter
First, cut the platinum-coated wire into two 6-inch-long pieces, and wind each piece into a little coiled spring that will serve as the electrodes in the fuel cell. The wires in the photo were wound on the end of the test lead of a volt meter, but a nail, an ice pick, or a coat hanger works nicely as a coil form.
Next, cut the leads of the battery clip in half and strip the insulation from the cut ends. Then twist the bare wires onto the ends of the platinum-coated electrodes, as shown in the photo at right. The battery clip and two wires will also be attached to the electrodes. These will later be used to connect to the volt meter.
Tape the electrodes securely to the Popsicle stick. Then tape the Popsicle stick to the glass of water, so that the electrodes dangle in the water for nearly their entire lengths. The twisted wire connections must stay out of the water, so only the platinum-coated electrodes are in the water.
Now connect the red wire to the positive terminal of the volt meter, and the black wire to the negative (or common) terminal of the volt meter. The volt meter should read 0 volts at this point, although a tiny amount of voltage may show up, such as 0.01 volt.
Your fuel cell is now complete.
To operate the fuel cell, touch the 9-volt battery to the battery clip (don't actually clip it on; you will only need it for a second or two).
Touching the battery to the clip causes the water at the electrodes to split into hydrogen and oxygen, a process called electrolysis. You can see the bubbles form at the electrodes while the battery is attached. Bubbles of hydrogen will cling to one electrode, and bubbles of oxygen will cling to the other.
Now remove the battery. If you did not use platinum-coated wire, you would expect the volt meter to read 0 volts again, since there would be no battery connected. But the platinum acts as a catalyst, allowing the hydrogen and oxygen to recombine — the hydrolysis reaction reverses! Instead of putting electricity into the cell to split the water, the hydrogen and oxygen combine make water again, and produce electricity.
You should initially get a little more than 2 volts from the fuel cell. As the bubbles pop, dissolve in the water, or get used up by the reaction, the voltage drops, quickly at first, then more slowly.
After a minute or so, the voltage declines much more slowly, as most of the decline is now due only to the gases being used up in the reaction that produces the electricity.
In this project you have stored the energy from the 9-volt battery as hydrogen and oxygen bubbles. You could, instead, bubble hydrogen and oxygen from some other source over the electrodes and generate electricity. Or you could produce hydrogen and oxygen during the day from solar power, store the gases, and then use them in the fuel cell at night. You could also store the gases in high-pressure tanks in an electric car, and generate the electricity the car needs from a fuel cell.
Why Does It Do That?
There are two things going on in this project — the electrolysis of water into hydrogen and oxygen gases, and the recombining of the gases to produce electricity. Let's look into each step separately.
The electrode connected to the negative side of the battery has electrons that are being pushed by the battery. Four of the electrons in that electrode combine with four water molecules (H2O). The four water molecules each give up a hydrogen atom, to form two molecules of hydrogen (H2), leaving four negatively charged ions of OH-.
The hydrogen gas bubbles up from the electrode, and the negatively charged OH- ions migrate away from the negatively charged electrode.
At the other electrode, the positive side of the battery pulls electrons from the water molecules. The water molecules split into positively charged hydrogen atoms (single protons), and oxygen molecules. The oxygen molecules bubble up, and the protons migrate away from the positively charged electrode.
The protons eventually combine with the OH- ions from the negative electrode, and form water molecules again.
The Fuel Cell
When you remove the battery, the hydrogen molecules clinging as bubbles to the electrode break up due to the catalytic action of the platinum, forming positively charged hydrogen ions (H, or protons) and electrons.
At the other electrode, the oxygen molecules stuck in bubbles on the platinum surface draw electrons from the metal, and then combine with the hydrogen ions in the water (from the reaction at the other electrode) to form water.
The oxygen electrode has lost two electrons to each oxygen molecule. The hydrogen electrode has gained two electrons from each hydrogen molecule. The electrons at the hydrogen electrode are attracted to the positively charged oxygen electrode. Electrons travel more easily in metal than in water, so the current flows in the wire instead of the water. In the wire, the current can do work, such as illuminating a light bulb or moving a volt meter.
Mirrors and Liquid Metal Alloys
Suppose you had a metal alloy that had the advantages of liquid mercury, but without the toxic effects?
You could make your own barometers and thermometers without having to worry about calling in a hazardous-materials team to clean up any accidents — you could simply wipe up the mess with a paper towel. You wouldn't have to worry about breathing toxic mercury fumes, but you could still make neat little electric motors that dip into liquid metal to make their electrical connections.
Suppose further that the metal would stick to glass, so you could paint it on glass to make your own mirrors. Or that it would stick to paper so you could draw your own electric circuits in it.
* Vial of gallium or gallium alloy (available from www.scitoys.com)
* Cotton swabs
* Glass microscope slide
* Glass slide slipcover (optional)
* Laser pointer (optional)
In the photo to the left are two small vials of liquid metal. The vial on the right contains gallium, an element that melts at 85.57ºF (29.76ºC). The vial on the left is an alloy that contains gallium, indium, and tin, and melts at -4ºF (-20ºC).
The gallium is liquid because the bottle was stored in a shirt pocket, next to a warm body. At room temperature it is a solid.
Because gallium expands when it solidifies (unlike most metals), the vials are only filled halfway. To get the solid metal out of the vial, simply warm it up in a cup of hot water until it melts.
Fun Projects with Liquid Metal
One fun thing you can do right away with the liquid metal alloy is make your own mirror. All it takes is a piece of glass and a cotton swab.
Dip the cotton swab in the vial, and twirl it around to coat it with the liquid metal alloy.
Now rub the coated swab on a glass microscope slide. The metal sticks to the glass, and makes an opaque reflective coating.
In the third photo on the left, I am holding the new mirror so that it reflects the view of the trees outside my window. The camera is focused on the window, so the trees and my hand are out of focus.
Being able to make your own mirrors is helpful when you need one that might be hard to find in stores. For example, I once needed a small lightweight mirror to glue to a speaker, so I could bounce a laser beam off of the speaker and have the music wiggle the mirror, which in turn made a pattern on the wall.
I used the liquid metal to coat a thin glass cover slip for a microscope slide.
The resulting mirror was very lightweight, and yet stiff, so it would remain flat while being bounced around by the speaker.
When it was glued onto the speaker and the music was turned on, the laser created a light show on the wall. Using two speakers, and bouncing the light off one and then off the other, I made a computer sound file that used both stereo channels to draw pictures on the wall.
Uses for Liquid Metal
There are lots of things you can do with liquid metal:
* Make thermometers
* Make barometers
* Make tilt meter seismographs
* Make nonconductive objects conductive
* Make electrodes that conform to varying surfaces
* Experiment with magnetohydrodynamics
* Conduct high-energy sound
* Replace mercury in spinning telescope mirrors
To keep the surface shiny, coat it with a diluted solution of hydrochloric acid or a thin layer of mineral oil. Both will prevent the slow oxidation of the metal that occurs over time.
Why Does It Do That?
Gallium is an element, atomic number 31, right below aluminum and just to the right of zinc in the periodic table of the elements. It starts out with a very low melting point, but when chemists add other elements it can achieve an even lower melting point.
Just below gallium in the periodic table is indium (element 49). Just to the right of indium is tin (element 50). When these elements are combined, their atoms bind together into a compound. The molecules of that compound do not bind to one another as strongly as the atoms of the original metals bound to each other. This lowers the melting point.
There are many ways to combine the three metals:
... and so on.
Each combination will have a slightly different melting point. Which do you think has the lowest melting point? This might make a good science fair experiment.
A mixture of 76 percent gallium and 24 percent indium melts at 61ºF (16ºC). Both gallium and this combination can be supercooled. That means that once melted, they can stay liquid even though they are cooled well below their melting points. Eventually a small crystal forms, and starts the whole batch solidifying, but small amounts can be kept supercooled for quite a while.
The gallium-indium alloy is more reflective than mercury, and is less dense, so it is being explored as a replacement for mercury in spinning liquid mirrors for astronomical telescopes.
When gallium is exposed to air, a thin layer of gallium oxide forms on the surface, just like what happens with aluminum, the metal just above it in the periodic table. This allows gallium alloys to wet almost any material, which means that instead of beading up, they spread out over the surface. This property makes gallium alloys good for making mirrors, and for coating objects to make them conductive.
In the same way that mercury alloys with other metals to make amalgams, gallium also alloys with other metals. When a small drop of gallium is placed aluminum foil, for example, it will combine with the aluminum to make a liquid with a crusty surface, as in the photo on page 10.
The alloy eventually combines with all of the aluminum, dissolving a hole in it.
If a drop of water is added to the resulting bead of liquid metal, the water combines vigorously with the aluminum, making a hot solution of caustic aluminum hydroxide. What is left is the original drop of gallium with a tiny amount of aluminum dissolved in it. (Don't put that drop back in the bottle; it will contaminate the rest of the gallium.)
This experiment can be done with either the gallium or the gallium-indium-tin alloy.
Homemade Ice Cream Without an Ice Cream Maker
Here is a way to make fresh homemade ice cream by hand in much less time than it normally takes with a home ice cream maker.
The ice cream freezes much faster because you prepare each serving in its own batch of ice and salt. Also, each serving is prepared in a thin, flat container, so the ice and salt can contact more of the ice cream at once.
* ½ cup sugar
* ¼ teaspoon salt
* 1 cup milk
* 3 beaten egg yolks
* 1 tablespoon vanilla extract
* 2 cups chilled whipping cream
* 2 cups fresh strawberries and extra ½ cup sugar (optional)
* Zip-lock sandwich bags
* Gallon-size zip-lock sandwich bags
* Ice cubes
* Rock salt
* Measuring cup
* Measuring spoons
* Mixing bowl
* Double boiler
* Wooden spoon
The cooking phase can be done a day or two ahead of time, so no one has to wait for the really fun part.
Set out all of the ingredients so everything is within easy reach.
Put the sugar, salt, and milk into the top pan of a double boiler. The water in the bottom of the double boiler will boil, and the temperature will never rise above the boiling point of water. This ensures that even if you get distracted you won't overcook the mixture.
Stir the 3 beaten egg yolks into the milk and sugar.
Cook the mixture over boiling water until you see bubbles forming around the edges.
The mixture is done when it is thick enough to coat the spoon.
Let the mixture cool to room temperature. When it has cooled, stir in the vanilla extract and the heavy whipping cream.
The fun part is about to begin. This is where having a bunch of kids around to help is really nice.
Pour a cup of the ice cream mixture into a plastic zip-lock sandwich bag.
Zip the bag, put it inside another sandwich bag for safety, and zip that one closed as well.
Fill a gallon-size food storage zip-lock bag about one third full of ice cubes. Add 1 cup of salt (we used rock salt, but any kind will do).
Zip the large bag closed, and wrap it in a towel to keep fingers from getting too cold.
Make a bag for everyone (this recipe will make enough for three or four servings, and you can double or quadruple the recipe if you're going to have a party).
Now have each person squish the little bag around in the salt and ice, making sure that the ice contacts the bag as much as possible, and that the bag gets lots of kneading, to keep the ice crystals tiny, so the ice cream will come out very smooth.
The kneading stage takes 10 minutes. You can let the ice cream sit in the ice for another 5 minutes if you like firmer ice cream, although continuing to knead it for the extra 5 minutes is also perfectly fine if you're having fun.
You will know the ice cream is done by feeling the mixture become a paste instead of a liquid. When you take the little bag out of the ice, wipe off the salt water, and then remove the outer bag carefully so you don't get salt in the ice cream. The bag will stand up in the bowl because it has turned into a frozen paste.
You can spoon the ice cream into a bowl if you like, or just eat it out of the bag.
If you like strawberry ice cream, mash 2 cups of strawberries with ½ cup sugar, and add ½ cup to each small bag before closing it up and putting it in the ice.
The result is an amazingly delicious homemade ice cream.
Why Does It Do That?
For ice to melt, it has to get heat from something. In this ice cream project, it gets the heat from the ice cream mixture (and from your hands, which is why they get cold while holding the bag). When the ice is melting, it is at 32ºF (0ºC).
When ice melts, the surface of the ice is wet. At the surface, there is solid ice on one side, and liquid water on the other. The boundary surface is exactly at the freezing point. This means that some water molecules are leaving the ice and moving into the water, but it also means that some liquid water is refreezing onto the ice. The system is in equilibrium when the rate of melting is equal to the rate of freezing, and this happens at 0ºC.
At equilibrium, the heat lost by the water as it freezes is equal to the heat gained by the ice as it melts.
Because plain ice can only barely cool something to the freezing point of water, something must be done to make it much colder than that, since the ice cream mixture freezes at a lower temperature than water.
Excerpted from Return of Gonzo Gizmos by Simon Quellen Field. Copyright © 2006 Simon Quellen Field. Excerpted by permission of Chicago Review Press Incorporated.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
Thoughts on Safety,
3 ELECTRICITY AND MAGNETISM,
4 COMPUTERS AND ELECTRONICS,