Saturday, November 20, 2010

Science projects & Models

A 30 second homopolar motor

We've built motors in 10 minutes, but this one really does go together in 30 seconds or less. You can time yourself once you have all the pieces in front of you.
homopolar motor parts
Click on image for a larger picture

What you need

  • A battery. A D cell, a C cell, or an AA cell -- any will do.
  • A disc magnet. Silver plated would be best, if it didn't tarnish, but gold doesn't have that problem. Nickel plated will do, but it won't work as well. The plating must conduct electricity.
  • A length of stranded wire, such as from an alligator test lead.
  • A sharp pointed wood or drywall screw. It must be magnetic, and it must conduct electricity.

homopolar motor parts
Click on image for a larger picture
Start the timer.
Set the screw in the center of the disk magnet.
Cut the alligator test lead in half, and strip the insulation from the last inch of the cut end, so the strands of wire spread out like a brush.
Hold the alligator clip against the flat end of the battery.
Bring the button end of the battery to touch the point of the screw, and lift the screw and magnet an inch off the table (the screw will stick to the battery because of the magnet).
Gently hold the brush end of the wire against the edge of the magnet.
Stop the timer, since the screw and magnet are spinning around like crazy.
You're done.

Science projects & Models

Make a Battery from Potato
Batteries generate electricity through a chemical reaction between two different electrodes and one electrolyte. Use of Copper and Zinc electrodes and Sulfuric acid as electrolyte is a proven method for this process. We are wondering if we can use any other liquid as electrolyte? This gave us the idea of using a potato as electrolyte. After all a fresh potato has a lot of juice that may serve our purpose as electrolyte.
Can Potato be used to generate electricity?
Potato juice contains many water soluble chemicals that may cause a chemical reaction with one or both of our electrodes. So we may get some electricity from that.
For this experiment we use:
  • A fresh potato
  • Copper Electrode
  • Zinc Electrode
  • A Digital or Analog Multimeter to measure Voltage or Current of produced electricity.
  • Alligator clips/ Leads
We insert copper and zinc electrodes in to the potato, close but not touching each other. We use Clip leads to connect our electrodes to the Multimeter to measure voltage between two electrodes or current passing through the multimeter. For this experiment we removed the shell of a broken AA battery for our Zinc electrode. (Make sure to test your multimeter by connecting it's Positive and Negative wires to each other that should show no current and no voltage).

Friday, November 12, 2010

Science Projects & Models

Making homemade plastic

Yep, we're surrounded by plastic.  Sit right there and look around the room and see if you can spot something made of plastic.  See, I told you so. The keys on your keyboard are made of plastic.  The mouse you've got your hand resting on is made of plastic.   Even parts of the monitor you're looking at right now is made of plastic (yikes... Reeko,  I don't know how you know all these things but stop it - it's giving me the creeps).
These plastics can be either natural plastics which are made of materials such as wax or natural rubber, or they can be synthetic plastics which are made from polyethylene or nylon.  Most plastic is made of petroleum oil.  The type of plastic we're fixing to make is of the natural type.
  1. Have an adult slowly warm 1/2 cup of heavy cream (or milk).
  2. When it begins simmering, stir in a few spoonfuls of vinegar (lemon juice will also work).
  3. Continue adding spoonfuls of vinegar and stirring until it begins to gel.
  4. Now let the it cool.
  5. Next, wash the rubbery stuff with water to clean it off. You'll have little plastic 'curds'.
Voila!  You have plastic!  If you want to really have some fun with it, take it to Dad and tell him you've been sitting out in the garage watching this stuff drip off from under the car for about an hour now.  Note: if he begins gathering up tools, it might be a good time to level with him...
The acid in the vinegar reacts with the casein in the milk making the plastic.  In practice, this type of plastic would be much too expensive for household use.   Oil-based plastics are much cheaper since the raw materials needed are much easier to come by.  But alas, even oil is a resource that will someday run out.   Scientists know this and are hard at work searching for new ways to make plastic.   Maybe you could be the one to find the answer...

Science Projects & Models

The process of extracting DNA from a cell is the first step for many laboratory procedures in biotechnology. The scientist must be able to separate DNA from the unwanted substances of the cell gently enough so that the DNA is not broken up.
It is both interesting and important to understand the reason for some of the steps in the procedure below. An onion is used because it has a low starch content, which allows the DNA to be seen clearly. The salt shields the negative phosphate ends of DNA, which allows the ends to come closer so the DNA can precipitate out of a cold alcohol solution. The detergent causes the cell membrane to break down by dissolving the lipids and proteins of the cell and disrupting the bonds that hold the cell membrane together. The detergent then forms complexes with these lipids and proteins, causing them to precipitate out of solution.
Materials and Equipment
This experiment is based on the use of household equipment and supplies.
  • two 4-cup measuring cups (1000 ml) with ml markings
  • one 1-cup measuring cup (250 ml) with ml markings
  • measuring spoons
  • sharp knife for cutting onion
  • large spoon for mixing
  • food processor or blender
  • thermometer that will measure 60°C (140°F), such as a candy thermometer
  • strainer or funnel that will fit in a 4-cup measuring cup
  • #6 coffee filter or cheese cloth
  • hot tap water bath (60°C)(a 3-quart saucepan works well to hold the water)
  • ice water bath (a large mixing bowl works well)
  • distilled water
  • light-colored dishwashing liquid or shampoo, such as Dawn® or Suave® Daily Clarifying Shampoo
  • large onion
  • table salt, either iodized or non-iodized
  • (optional) meat tenderizer that contains papain, such as Adolph's
  • 1 test tube, preferably with a cap, that contains the onion solution. (A narrow glass container, such as a liqueur glass or clear bud vase can substitute for the test tube.)
  • pasteur pipettes or medicine droppers
  • 95% ethanol (grain alcohol). (Note: Make sure to purchase 95% ethanol, not methanol.
  • kitchen timer
  • (optional) meat tenderizer and flat toothpicks
Experimental Procedure
  1. Prepare two water baths—one at 55-60°C and another filled with ice and water, around 4°C. For the hot water bath, a large metal pot can be used along with a thermometer with an appropriate temperature range. For the ice bath, a mixing bowl filled with ice and water works well.
  2. For each onion, make a solution consisting of one tablespoon (10 ml) of liquid dishwashing detergent or shampoo and one level 1/4 teaspoon (1.5 g) of table salt. Put in a 1-cup measuring cup (250 ml beaker).

    Add distilled water to make a final volume of 100 ml. Dissolve the salt by stirring slowly to avoid foaming.

  3. Coarsely chop one large onion with a food processor or blender (may be done by hand if neither is available) and put into a 4-cup measuring cup (1000 ml). For best results, do not chop the onion too finely. The size of the pieces should be like those used in making spaghetti. It is better to have the pieces too large than too small.

  4. Cover chopped onion with the 100 ml of solution from step #2. The liquid detergent causes the cell membrane to break down and dissolves the lipids and proteins of the cell by disrupting the bonds that hold the cell membrane together. The detergent causes lipids and proteins to precipitate out of the solution. NaCl enables nucleic acids to precipitate out of an alcohol solution because it shields the negative phosphate end of DNA, causing the DNA strands to come closer together and coalesce.

  5. Put the measuring cup in a hot water bath at 55-60°C for 10-12 minutes. During this time, press the chopped onion mixture against the side of the measuring cup with the back of the spoon. (Do not keep the mixture in the hot water bath for more than 15 minutes because the DNA will begin to break down.) If using a large metal pot for water bath, remove the pot from the stove before placing the onion-containing measuring cup inside—the procedure is safer if the pot is off the burner. Continue to monitor temperature of water bath and make adjustments as needed (i.e., adding hot or cold water).

    The heat treatment softens the phospholipids in the cell membrane and denatures the DNAse enzymes which, if present, would cut the DNA into small fragments so that it could not be extracted.

  6. Cool the mixture in an ice water bath for 5 minutes. During this time, press the chopped onion mixture against the side of the measuring cup with the back of the spoon. This step slows the breakdown of DNA.

  7. Filter the mixture through a #6 coffee filter or four layers of cheese cloth placed in a strainer over a 4-cup measuring cup. When you filter the onion mixture, try to keep the foam from getting into the filtrate. It sometimes filters slowly, so you might want to put the whole set up in the refrigerator and let it filter overnight.

  8. Dispense the onion solution into a test tube. The test tube should contain about 1 teaspoon of solution or be about 1/3 full. For most uniform results among test tubes, stir the solution frequently when dispensing it into the tubes. There is not an advantage to dispensing more than one teaspoon of solution into a test tube. The solution can be stored in a refrigerator for about a day before it is used for the laboratory exercise. When the solution is removed from the refrigerator, it should be gently mixed before the test tubes are filled.

  9. (Optional) Add two toothpicks full of meat tenderizer to the onion solution, cap the tube, and mix gently to avoid foaming. Meat tenderizer contains papain, an enzyme that will clean extra proteins away from DNA.

  10. Add cold alcohol to the test tube to create an alcohol layer on top of about 1 cm. For best results, the alcohol should be as cold as possible. The alcohol can be added to the solution in at least three ways:

    (a) Fill a pasteur pipette with alcohol, put it to bottom of the test tube, and release the alcohol.
    (b) Or, put about 1 cm of alcohol into the bottom of a test tube and add the onion solution.
    (c) Or, slowly pour the alcohol down the inside of the test tube with a pasteur pipette or medicine dropper.

    DNA is not soluble in alcohol. When alcohol is added to the mixture, all the components of the mixture, except for DNA, stay in solution while the DNA precipitates out into the alcohol layer.

  11. Let the solution sit for 2-3 minutes without disturbing it. It is important NOT to shake the test tube. You can watch the white DNA precipitate out into the alcohol layer. When good results are obtained, there will be enough DNA to spool on to a glass rod, a pasteur pipette that has been heated at the tip to form a hook, or similar device. A wooden skewer or nut pick (small metal rod with curved tip) may also work well for spooling DNA if Pasteur pipette is unavailable. DNA has the appearance of white mucus.

Science Projects & Models


List of materials:
This is the minimum list of material you need for your experiment.
  1. Miniature light bulb (low voltage, low current)
  2. Miniature base for light bulb
  3. Pair of insulated solid copper wire AWG=20
  4. Pair of alligator clips
  5. Magnesium Electrodes
  6. Iron Electrodes
  7. A cup of saltwater
  8. Screws for the miniature base.   

Additional optional materials you may use:
  1. A wooden board to mount the miniature base (light holder)
  2. Plastic container about 4" x 4" x 4"
  3. Hydrogen Peroxide
  1. Remove the plastic insulation of about one inch from both ends of the wires. 
  2. Loosen the screw on both contacts of the bulb holder. Place one end of the red wire under one screw, make a loop and then tighten the screw. Place one end of the black wire under the other screw, make a loop and then tighten the screw. 
  3. Pass the open end of the red wire through the arm of the red alligator clip and secure it under the screw.
  4. Pass the open end of the black wire through the arm of the black alligator clip and secure it under the screw. 
  5. Screw the light bulb on the miniature base.
  6. Connect the red alligator clip to the iron electrode and secure it on one side of the plastic container or the cup.
  7. Connect the black alligator clip to the magnesium electrode and secure it on the opposite side of the container. (You may need to hold them by hand or use a small tape to hold them in place on the side of the container.
  8. In another pitcher, prepare some strong, warm salt water. Add enough salt so at the end some salt will be left at the bottom of the pitcher.
  9. Transfer the salt water from the pitcher to the container. 
  10. At this time, if all the connections are secure and the electrodes are large enough, you should get a light.
 How can I get more light?
  1. Make sure your electrodes are not touching each other.
  2. Make sure there is nothing blocking the space between the electrodes.
  3. Make sure that the alligator clips are not touching the salt water.
  4. Both electrodes must have the maximum possible surface contact with salt water.
The test tube electrodes (magnesium electrodes in test tubes) are formed like a spring. This provides the largest possible surface contact. For Iron electrode you may use steel wool. Steel wool has a very large surface contact. A steel screen may work as well.
You may notice that you will get more light if you stir the solution or if you remove the iron electrode and insert it back again. Such actions provide oxygen to the surface of the iron.
In this case you may add some oxygen (in the form of hydrogen peroxide) to the salt water. That should immediately increase the light.

Sunday, November 7, 2010

Science Projects & Models

The egg in a bottle demonstration is an easy chemistry or physics demonstration you can do at home or in the lab. You set an egg on top of a bottle (as pictured). You change the temperature of the air inside the container either by dropping a piece of burning paper into the bottle or by directly heating/cooling the bottle. Air pushes the egg into the bottle.

Egg in a Bottle Materials
  • peeled hard-boiled egg (or soft-boiled, if a yolk mess interests you)
  • flask or jar with opening slightly smaller than the diameter of the egg
  • paper/lighter or very hot water or very cold liquid
In a chemistry lab, this demonstration is most commonly performed using a 250-ml flask and a medium or large egg. If you are trying this demonstration at home, you can use a glass apple juice bottle. I used a Sobe™ soft drink bottle. If you use too large of an egg, it will get sucked into the bottle, but stuck (resulting in a gooey mess if the egg was soft-boiled). I recommend a medium egg for the Sobe™ bottle. An extra-large egg gets wedged in the bottle.
Perform the Demonstration
  • Method 1: Set a piece of paper on fire and drop it into the bottle. Set the egg on top of the bottle (small side pointed downward). When the flame goes out, the egg will get pushed into the bottle.
  • Method 2: Set the egg on the bottle. Run the bottle under very hot tap water. Warmed air will escape around the egg. Set the bottle on the counter. As it cools, the egg will be pushed into the bottle.
  • Method 3: Set the egg on the bottle. Immerse the bottle in a very cold liquid. I have heard of this being done using liquid nitrogen, but that sounds dangerous (could shatter the glass). I recommend trying ice water. The egg is pushed in as the air inside the bottle is chilled.
How It Works
If you just set the egg on the bottle, its diameter is too large for it to slip inside. The pressure of the air inside and outside of the bottle is the same, so the only force that would cause the egg to enter the bottle is gravity. Gravity isn't sufficient to pull the egg inside the bottle.
When you change the temperature of the air inside the bottle, you change the pressure of the air inside the bottle. If you have a constant volume of air and heat it, the pressure of the air increases. If you cool the air, the pressure decreases. If you can lower the pressure inside the bottle enough, the air pressure outside the bottle will push the egg into the container.
It's easy to see how the pressure changes when you chill the bottle, but why is the egg pushed into the bottle when heat is applied? When you drop burning paper into the bottle, the paper will burn until the oxygen is consumed (or the paper is consumed, whichever comes first). Combustion heats the air in the bottle, increasing the air pressure. The heated air pushes the egg out of the way, making it appear to jump on the mouth of the bottle. As the air cools, the egg settles down and seals the mouth of the bottle. Now there is less air in the bottle than when you started, so it exerts less pressure. When the temperature inside and outside the bottle is the same, there is enough positive pressure outside the bottle to push the egg inside.
Heating the bottle produces the same result (and may be easier to do if you can't keep the paper burning long enough to put the egg on the bottle). The bottle and the air are heated. Hot air escapes from the bottle until the pressure both inside and outside the bottle is the same. As the bottle and air inside continue to cool, a pressure gradient builds, so the egg is pushed into the bottle. 

How to Get the Egg Out
You can get the egg out by increasing the pressure inside the bottle so that it is higher than the pressure of the air outside of the bottle. Roll the egg around so it is situated with the small end resting in the mouth of the bottle. Tilt the bottle just enough so you can blow air inside the bottle. Roll the egg over the opening before you take your mouth away. Hold the bottle upside down and watch the egg 'fall' out of the bottle. Alternatively, you can apply negative pressure to the bottle by sucking the air out, but then you risk choking on an egg, so that's not a good plan.

Science Projects & Models

Make your fingers smoke when you rub them together and glow in the dark. All you need is a matchbox and a way to burn the striker portion.
Here's How:
  1. Cut out the striker portion of a matchbox from a box of safety matches. Trim off any paper around the striker.
  2. Fold the striker in half, striker-sides facing each other.
  3. Set the folded striker on top of the running cold water faucet or a refrigerated metal pan.
  4. Use a lighter to set fire to the striker. Ignite both ends. Then run the lighter along the length of the folded striker. It won't burn to ash, which is fine.
  5. Discard the burned striker.
  6. You will see a brown residue that has been deposited along the top of the faucet or metal pan. Run your fingertip along the residue to pick it up.
  7. Slowly rub your finger and thumb together. If you do this in the dark, your fingers will have a greenish glow. Very, very cool.


  1. Wash your hands after doing this, and try to avoid breathing in the smoke. The trick probably involves white phosphorus, which can be absorbed through your skin and is toxic.
  2. If you don't have scissors, you can do this trick by tearing off the striker portion of the matchbox with your fingers. It's just easier to cut out the striker, if you can.
  3. You could use the matches in the matchbox, rather than a lighter, of course.

What You Need:

  • matchbox of safety matches
  • cold water faucet or chilled pan
  • scissors
  • lighter

Science Projects & Models

This is a neat 'magic trick' that illustrates the process of combustion, the flammability of alcohol, and the special qualities of the material used to make currency.
Scientific Concept behind Burning Money
A combustion reaction occurs between alcohol and oxygen, producing heat and light (energy) and carbon dioxide and water.
C2H5OH + 4 O2 -> 2 CO2 + 3 H2O + energy
When the bill is soaked an alcohol-water solution, the alcohol has a high vapor pressure and is mainly on the outside of the material (a bill is more like fabric than paper, which is nice, if you've ever accidentally washed one). When the bill is lit, the alcohol is what actually burns. The temperature at which the alcohol burns is not high enough to evaporate the water, which has a high specific heat, so the bill remains wet and isn't able to catch fire on its own. After the alcohol has burned, the flame goes out, leaving a slightly damp dollar bill.
Here's what you need to do the demonstration...

Here is what you need to perform the burning money demonstration:
  • dollar bill (higher denomination if you're brave)
  • tongs
  • matches or a lighter 
  • flame
  • solution of 50% alcohol and 50% water (you can mix 95% alcohol with water in a 1:1 ratio, if desired)

salt (or one of these chemicals if you want a colored Flame Colorants

Lithium Chloride
Strontium Chloride
Calcium Chloride (a bleaching powder)
Sodium Chloride (table salt)
or Sodium Carbonate
Yellowish Green
Copper Sulfate or Boric Acid
Copper Chloride
3 parts Potassium Sulfate
1 part Potassium Nitrate (saltpeter)
Potassium Chloride
Magnesium Sulfate (Epsom salts)

Have you gathered your materials? Let's burn money...
  1. Prepare the alcohol and water solution. You can mix 50 ml of water with 50 ml of 95-100% alcohol.
  2. Add a pinch salt or other colorant to the alcohol/water solution, to help produce a visible flame.
  3. Soak a dollar bill in the alcohol/water solution so that it is thoroughly wet.
  4. Use tongs to pick up the bill. Allow any excess liquid to drain. Move the damp bill away from the alcohol-water solution.
  5. Light the bill on fire and allow it to burn until the flame goes out.

Science Projects & Models

Fireworks are a beautiful and fun part of many celebrations, but not something you want kids to make themselves. However, even very young explorers can experiment with these safe underwater 'fireworks'.

What You Need
  • water
  • oil
  • food coloring
  • tall clear glass
  • another cup or glass
  • fork
Create Fireworks in a Glass
  1. Fill the tall glass almost to the top with room-temperature water. Warm water is ok, too.
  2. Pour a little oil into the other glass. (1-2 tablespoons)
  3. Add a couple of drops of food coloring. I used one drop of blue and one drop of red, but you can use any colors.
  4. Briefly stir the oil and food coloring mixture with a fork. You want to break up the food coloring drops into smaller drops, but not thoroughly mix the liquid.
  5. Pour the oil and coloring mixture into the tall glass.
  6. Now watch! The food coloring will slowly sink in the glass, with each droplet expanding outward as it falls, resembling fireworks falling into water.
How It Works
Food coloring dissolves in water, but not in oil. When you stir the food coloring in the oil, you are breaking up the coloring droplets (though drops that come into contact with each other will merge... blue + red = purple). Oil is less dense than water, so the oil will float at the top of the glass. As the colored drops sink to the bottom of the oil, they mix with the water. The color diffuses outward as the heavier colored drop falls to the bottom.