Saturday, July 9, 2011

Catch Snowflakes

What you will need:

  • Black velvet or black construction paper
  • Magnifying Glass
  • Snow

Since snowflakes melt so quickly you need to freeze your cloth or paper. Have the cloth or paper frozen and ready to go for the next snowfall. Place the cloth or paper outside and let some snowflakes land on the dark surface. Quickly, before they melt, examine the snowflakes with a magnifying glass. Many snowflakes are "broken" and so you don't see the whole six-sided crystal, but with persistence you'll see some beautiful examples.

Make Your Own Snow Guage

What you will need:

  • A 2-liter plastic soda pop bottle
  • A ruler
  • Scissors
  • Permanent marker

Take the 2-litre pop bottle and remove the outside wrapper. Then use the scissors to cut off the top half. Take the ruler and hold it up against the bottom half of the pop bottle. Using the permanent marker, mark the outside of the bottle in centimeters or inches. You now have your own snow gauge! You will want to place it outside so it can collect the falling snow.

Hint: Don't place it close to buildings. The gauge might not collect as much because the building will block some of the falling snow.

Sky in a Jar

What you will need:
  • a clear, straight-sided drinking glass, or clear plastic or glass jar
  • water
  • milk
  • measuring spoons
  • flashlight
  • a darkened room


  1. Fill the glass or jar about 2/3 full of water (about 8 - 12 oz.)
  2. Add 1/2 to 1 teaspoon milk and stir.
  3. Take the glass and flashlight into a darkened room.
  4. Hold the flashlight above the surface of the water and observe the water in the glass from the side. It should have a slight bluish tint. Now, hold the flashlight to the side of the glass and look through the water directly at the light. The water should have a slightly reddish tint. Put the flashlight under the glass and look down into the water from the top. It should have a deeper reddish tint.

What's happening:

The small particles of milk suspended in the water scattered the light from the flashlight, like the dust particles and molecules in the air scatter sunlight. When the light shines in the top of the glass, the water looks blue because you see blue light scattered to the side. When you look through the water directly at the light, it appears red because some of the blue was removed by scattering.

Make Your Own Cloud

What you will need:
  • warm water
  • jar
  • ice
  • metal dish


Place the ice in the metal dish. Let it stand until it gets very cold. Once the dish is cold, place 1 inch of warm water in the jar.

Place the metal dish over the top of the jar. As the warm water evaporates, it will encounter the cold dish. The moisture will then condense and form a cloud.

Make Your Own Wind Vane

Before You Start...

A weather vane is also called a wind vane. It is a tool for measuring wind direction. It spins on a rod and points in the direction from which the wind comes.

The weather vane is one of the oldest weather tools. The part of the vane that turns into the wind is usually shaped like an arrow. The other end is wide so it will catch the smallest breeze. The breeze turns the arrow until it catches both sides of the wide end equally. The arrow always points into the wind. The arrow tells you the direction from which the wind is coming.

What you will need:

  • paper and pencil
  • scissors
  • cardboard
  • compass
  • plastic soft drink bottle
  • plastic drinking straw
  • shallow pan filled with rocks
  • felt marking pen


What is a weather vane? When have you seen weather vanes? Write down your answers. Draw a picture of a weather vane.

With the scissors, carefully cut an arrow with a tab from the tag board, as shown. Remember that scissors are sharp, so handle them carefully. Bend the tab slightly so the arrow turns easily when you put it in one end of the straw. Put the other end of the straw in the bottle. Remove enough rocks from the pan to make room for the bottle. Pile the rocks back around the bottle so it won't be blown over. (See illustrations above.)

A compass always point north. Use your compass to find north, and then mark the four sides of the bottle E, W, N, and S with a felt pen.

Set your weather vane in a high place such as the top of a playhouse or a slide. Make sure it does not wobble or tilt, and that it catches the slightest breeze.

Watch your weather vane closely and then describe how it works. Test it on windy days and again when there is just a light breeze.

Background Information:

A weather vane is a tool used to tell which direction the wind is coming from. Weather vanes are usually found on top of buildings so they will catch an open breeze. Look for them on top of barns, houses, weather stations, hardware stores, and other places that sell or use weather tools. The part of the vane that turns into the wind is usually shaped like an arrow. The other end is wide so it will catch the smallest breeze. Sometimes a metal rooster or other animal sits on top of the weather vane.

You have made a weather vane! If the wind is blowing from the south, the wind is usually warm. If the wind is blowing from the north, the wind is usually cooler.

Some weather vanes have directional strips underneath the arrow to make it easier to read. Your markings on the bottle do the same thing.

The breeze turns the arrow on the weather vane until it catches both sides of the wide equally. The arrow always points into the wind.

It is easier to see how the energy from the wind moves your weather vane if it is up high and in an open area. You might also want to experiment by putting it on the ground.

A weather vane is one of the oldest weather tools. It is still used today to measure the direction of the wind. Weather vanes can only measure wind direction a few yards (meters) off the ground. Large, helium-filled weather balloons are used to measure winds high above the earth's surface. The balloons move with the same speed and direction as the wind.

Make Your Own Anemometer

Its easier to make than pronounce! You can make your own anemometer to measure the wind speed.

What you will need:

  • five 3 ounce paper Dixie cups
  • two straight plastic soda straws
  • a pin
  • scissors
  • paper punch
  • small stapler
  • sharp pencil with an eraser


Take four of the Dixie cups. Using the paper punch, punch one hole in each, about a half inch below the rim.

Take the fifth cup. Punch four equally spaced holes about a quarter inch below the rim. Then punch a hole in the center of the bottom of the cup.

Take one of the four cups and push a soda straw through the hole. Fold the end of the straw, and staple it to the side of the cup across from the hole. Repeat this procedure for another one-hole cup and the second straw.

Now slide one cup and straw assembly through two opposite holes in the cup with four holes. Push another one-hole cup onto the end of the straw just pushed through the four-hole cup. Bend the straw and staple it to the one-hole cup, making certain that the cup faces in the opposite direction from the first cup. Repeat this procedure using the other cup and straw assembly and the remaining one-hole cup.

Align the four cups so that their open ends face in the same direction (clockwise or counterclockwise) around the center cup. Push the straight pin through the two straws where they intersect. Push the eraser end of the pencil through the bottom hole in the center cup. Push the pin into the end of the pencil eraser as far as it will go. Your anemometer is ready to use.

Your anemometer is useful because it rotates at the same speed as the wind. This instrument is quite helpful in accurately determining wind speeds because it gives a direct measure of the speed of the wind. To find the wind speed, determine the number of revolutions per minute. Next calculate the circumference of the circle (in feet) made by the rotating paper cups. Multiply the revolutions per minute by the circumference of the circle (in feet per revolution), and you will have the velocity of the wind in feet per minute. The anemometer is an example of a vertical-axis wind collector. It need not be pointed into the wind to spin.

Make Your Own Barometer

Do you know what the air pressure is today? You can find out for yourself by measuring the air pressure on a barometer.

What you will need:

  • plastic wrap
  • scissors
  • straw
  • index card
  • rubber band


  1. COVER the top of the can with plastic wrap. USE a rubber band to hold the plastic wrap in place. The cover should be taut making the can airtight.
  2. PLACE the straw horizontally on the plastic wrap so that two-thirds of the straw is on the can.
  3. TAPE the straw to the middle of the plastic wrap.
  4. TAPE the index card to the can behind the straw.
  5. Carefully RECORD the location of the straw on the index card.
  6. After 15 minutes, RECORD the new location of the straw on the index card.
  7. Continue CHECKING and RECORDING the straw location as often as desired.
  8. Be careful not to place your barometer near a window, as the barometer is sensitive to temperature as well as air pressure.

What's happening:

High pressure will make the plastic wrap cave in, and the straw go up. Low pressure will make the plastic wrap puff up, and the straw go down. Check your measurements with the barometer reading you see on the local news.

Make Your Own Thunderstorm

What you will need:

  • 1 clear plastic container, shoebox size
  • red food coloring
  • ice cubes made with water dyed with blue food coloring
  • colored pencils
  • index cards


  1. Fill container 2/3 full with room temperature water.
  2. Let the water sit for 30 seconds until completely still.
  3. Place a blue ice cube at one end of the plastic container.
  4. Add two drops of red food coloring to the water at the opposite end of the plastic container. Be careful not to disturb the water.
  5. Observe where the red and blue food coloring goes.
  6. Using the red and blue pencils draw what you see happening.

What's happening:

It's all about convection! The cold water sinks while the warmer red water rises, or stays higher than the blue. Convection is the action of warm air rising and cold air sinking. You probably guessed that the blue water represents a cold air mass and the red water represents the warm, unstable air mass. A thunderstorm is caused by unstable air and convection plays an important part. A body of warm air is forced to rise by an approaching cold front. Other things can cause warm air to rise, like a mountain slope.

A strong, persistent updraft of warm moist air is formed and lifted by the approaching cold front. Speeds in an updraft can be as fast as 90 miles per hour! The air cools as it rises, condenses, and forms cumulus clouds. When condensation occurs, heat is released and helps the thunderstorm grow.

At some point, condensation high in the cloud (now in the form of water droplets and ice) falls to the ground as rain. A cold downdraft forms as the rain falls.

"See" Air Pressure

"See" Air Pressure

How powerful is air pressure? Can it crush a can? Conduct the experiment below to find out. You will need the help of your parents for this experiement!

What you will need:

  • hot plate
  • empty soft drink can
  • tongs to pick up a hot soft drink can
  • shallow pan filled with cool water


PLACE a spoonful of water into the can. PLACE the can open side up onto a heated hotplate. As the water temperature rises, the can will fill with water vapor and steam will escape from the can's opening. USE the tongs to quickly PLACE the can, open end first (upside down), into the shallow pan filled with cool water. Quickly, the can will be crushed, and will give off a dull "pop" sound.

What's happening: The air pressure decreases as the water vapor condenses inside the can. The can is crushed because the air pressure inside the can is less than the air pressure outside the can.

Tornado Generator Box

TORNADO GENERATOR BOX (c)1996 William J. Beaty

SCIENCE FAIR NOTES: If you don't need the device to last forever, you
could build this out of cardboard or "gatorfoam" instead of plexiglas.
Use duct tape instead of glue, and use incense sticks to make "smoke"
instead of a humidifier. The bottom panel should not be cardboard,
since it's a fire hazard with incense, or humidifier mist will make it
soggy after awhile. If you use opaque materials, then make a big hole
in one of the side panels and tape clear plastic over it to form a
window. The fan creates the tornado, and the mist or incense smoke
makes it visible. Instead of using an ultrasonic humidifier, you can
use burning incense sticks or cones, but supply a large dish or pan on
the bottom so the burning incense cannot become a fire hazard! If
desired, put a small (15W) light bulb at the rear of the chamber to
light up the mist tornado, and paint the inside of the chamber black to
give good contrast. Try using the "12-volt micro fan" from Radio
Shack, part number 273-240, and run it from a 9V battery. However,
if the slots in the side of your tornado box are too wide, you'll need
a more powerful fan.

Top view of the tornado box looks like this (if the square top panel is
removed) :
|| four 14" x 24" panels,
=========================== || at least one is clear
|| (glass, acrylic, or
|| || cut a hole and cover it
|| || TOP VIEW with stretched plastic
|| || film.)
|| ||
|| ||
|| ============================= panels are positioned to
|| form four slots at the
|| (-------- about 14" --------) corners.

The four vertical panels are fastened to square top and bottom plates, but
are not fastened to each other. Gaps between the vertical panels form the
slots. With 18in square top and bottom panels, and 14in walls, the slots
are 1in across, and the square central chamber is 12in. Air rushes in
through the narrow slots at the four corners, swirls inwards to form the
tornado, then exits through the the top. A small fan was installed in the
center of the top plate (with a hole cut for the fan.) The device can be
any size, keeping the scale of the slots about the same of course: with a
12" square inner chamber, the slots end up being about 1" across. The
total height is up to you. My device was about 2ft. tall. If you make
yours lots taller, you either need to use a fairly strong fan, or you need
to make the width of the slots smaller.

"Touch the
exhibit article for more info on humidifiers.

The shallow funnel-shape allows the water which builds up in the bottom of
the tornado chamber to run back into the humidifier, rather than pooling
up in the bottom of the chamber and growing algae. Over the heat-formed
funnel I placed a 6" dia. perforated plexiglas disk with 1/8" legs around
the edge. The legs raise up the circular plate so water can run past the
edge, but the slot is narrow enough that debris from museum visitors won't
end up in the humidifier water. The perforations in this flat plate were
closely-spaced 1/4" holes made in a large circle, and the mist from the
humidifier exits through these holes. It is important to provide a
central, flat, unperforated surface for the vortex to "work against", and
therefore this plate has an unperforated center, with a circle of holes
about 3" dia. to feed mist into the vortex from around its perimeter.

I found that optical contrast is important, so I made the two back walls
opaque black, the bottom funnel and plate black, and two front walls
transparent, then I lighted the whole thing heavily from the top and from
slightly behind. If I had to do it over again, I might try installing a
flourescent tube running the length of the box. This tube would need to
be in the rear from the viewpoint of users, but with some sort of light
shields added, so it illuminates the mist column from behind, but doesn't
shine directly in the user's eyes.

To allow people to stick their hands inside, I cut the vertical slot in
the front of the box larger at the bottom, as shown below. This distorts
the vortex, but allows "hands on" access. If you use a tiny, weak fan,
you probably should skip this part, since the large hole will divert air
from the vertical slots and prevent the vortex from forming.

_____ boxer fan
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
---___ ====== __----
--_ _--
| |

And last, I built a small electronic controller which allowed users to
vary the fan speed by pushing and holding a "faster" and "slower" button.
(Speed control knobs tend to get wrecked pretty fast in an exhibits
environment, while pinball machine flipper-buttons are long-lasting.) As
the fan runs faster and faster, the tornado suddenly undergoes transition
to turbulence, changing from an onion-layered smoke column into a whirling
turbulent cloud. To preserve the contents of the water tank, the
controller would disable the humidifier if none of the buttons were pushed
for about two minutes. Once the mist had started, there was one last
button which allowed the user to turn the mist off and on, and even to
make "pulses" of mist which would travel upwards in the vortex.

The speed of the fan and the size of the slots must be adjusted correctly
in order to create a robust vortex. I used a handheld incense stick to
inject smoke into the air so I could see if the vortex was working. If
your fan is too powerful, the vortex will be turbulent and won't create
beautiful complicated "onion layers" of laminar flow in the smoke pattern.
The fan's air stream can be slowed by partially blocking its exit with
cardboard and duct tape. If the side slots of the main chamber are too
large and the fan too weak, the vortex will form very slowly and will
vanish at the slightest disturbance. If this occurs, either move the
chamber walls to make the side slots smaller, or find a more powerful fan.

Forever on my "wish list" was to install a scanned laser beam "sheet-of-
light" generator. This would allow visual cross-sections of the mist to
be created. Simply aiming a handheld laser through the rear slot of the
chamber and waving the beam rapidly back and forth through the mist caused
momentary but spectacular "wind tunnel" turbulence patterns to appear, but
I never went any further with this. Shielding the beam would be an issue,
since to be efficient, the illumination must be directed through the mist
column from behind, and towards (but not hitting) the users' eyes.

Other ideas for variations: a sculptor in New York converted an entire
room into a tornado chamber. He/she provided a large exhaust fan in the
center of the ceiling, then arranged a large circle of vertical pipes into
the shape of a skeletal cylinder, with the center of the cylinder pattern
aligned with the ceiling fan. These pipes extended from floor to ceiling,
and each pipe presumably contained its own fan, and a series of holes or
slots running one along side of the pipe. The pipe slots blew air
sideways so all the air in the room rotated slowly, and the central fan
pulled air towards the center of the circle. The large "cylinder" of
pipes acts as the walls of the chamber and provides tangential air jets,
so any air which flows towards the center of the room is forced to spiral
inwards. A powerful vortex forms in the center of the room, extending
from floor to ceiling. A big pile of leaves, shredded plastic, etc.
completes the exhibit.

The Exploratorium museum in San Francisco contains one large, famous
example of a tornado generator chamber. ( Only two
walls are provided, the walls being made of huge curved sheets of
plexiglas, with a fan in the ceiling of the exhibit. Ultrasonic
humidifiers provide mist in the floor of the exhibit. Children can walk
into the device and interrupt the spinning mist vortex.

Make Lightning

What you will need:
  • styrofoam plate
  • thumbtack
  • pencil with new eraser
  • aluminum pie pan
  • small piece of wool fabric


  1. Push the thumbtack through the center of the aluminum pie pan from the bottom.
  2. Push the eraser end of the pencil into the thumbtack. (The pencil becomes a handle to lift the pan.)
  3. Put the styrofoam plate upside-down on a table. Rub the underside of the plate with the wool fabric for one minute. Make sure you rub hard and fast!
  4. Pick up the pie pan using the pencil "handle" and place it on top of the upside-down plate.
  5. Touch the pie pan with your finger. If you don't feel anything when you touched the pan, try rubbing the plate again.
  6. Try turning out the lights before you touch the pan. Can you see anything happen when you touch the pan?

What's happening:

It's all about static electricity! Lightning happens when the negative charges (electrons) in the bottom of the cloud ( and your finger) are attracted to the positive charges (protons) in the ground (and the pie pan). The resulting spark is like a mini bolt of lightning.

The accumulation of electric charges has to be great enough to overcome the insulating properties of air. When this happens, a stream of negative charges pours down towards a high point where positive charges have clustered due to the pull of the thunderhead.

The connection is made and the protons rush up to meet the electrons. It is at that point that we see lightning and hear thunder. A bolt of lightning heats the air along its path causing it to expand rapidly. Thunder is the sound caused by rapidly expanding air.

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