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Science Demonstrations

Science Demonstrations, Science Experiments, Science Activities


 


 

 

RINGING ROD DEMO LESSON PLAN

Robert Ruisinger

For grades 7-12 (physics)

Materials: Metal rod about one meter or less in length, and some rosin.

Procedure: Find the midpoint of the rod by balancing it on one finger. Hold it in your hand at the midpoint that you just determined. rub the rosin on your other hand between your thumb and your index finger. Now slide your hand down the bottom half of the metal rod with light pressure. The rod will begin to "whine" a screeching sound if done correctly. The more you slide your fingers down it, the louder it gets.

Concept: By holding the rod at it's center, you are allowing it to act like a wave. The center is the node of the wave, and both sides resonate as you apply the frictional vibration. By pulling your "sticky" fingers down the rod, you are causing a vibration, and at certain levels you can hear this vibration.

You can tie this demo into a lesson on frequency, wave motion, or sound. You can also obtain a wave with more than one node. By finding the center of one of the halves you have already and holding it there. You now have three nodes. You will need to apply a significant force of vibration, because this frequency is much higher. Any more nodes are usually not going to be heard. You can experiment with different length rods, though.

Credits: Bonnstetter, 1995

Jim Wright

SUBJECT AREA Physics

CONCEPTS COVERED BY DEMO

  1. Inertia
  2. Kinetic energy
  3. Potential energy
  4. Friction

"Can" You Come Back!

Materials:

  1. A coffee can with plastic lid
  2. An object to use as a weight (The object must be heavy enough to resist movement while suspended by rubber band. Some experimentation may be necessary)
  3. Two rubber bands or one if it is large enough to reach both end of the can plus be attached to the weight

Procedure: Some assembly required.

  1. Punch a two holes in the metal end of the can and also in the plastic end of the can
  2. Push the rubber band through the holes and place a tooth pick through the loops.
  3. Attach the weight to the rubber band in the center of the can and replace the plastic lid.

Experiment and demo Roll the can across a level surface. The can will roll and stop and then return close to the original starting point.

Questions:

  1. Why does the can roll away from you?
  2. Why does the can stop?
  3. What makes the can return to you?
  4. What is inside of the can that could cause this to happen?

Rationale: This demo uses several principles that could be talked about and worked with in class. By using your hand to push the can originally kinetic energy was used. While the can was rolling the rubber band inside was being twisted and therefore potential energy was being stored. The weight in the middle of the rubber band was heavy enough that it's own inertia prevented it from turning with the can. When the can stopped due to friction and the energy taken up by the rubber band the potential energy in the rubber band was released. Since the weight was heavier than the can, it was easier for the can to roll than for the weight to turn. Therefore the can rolled back toward your hand until the energy in the rubber band could not over come the friction of the can being rolled.

Resources: Wizard

SUBJECT AREA (Chemistry, Atmospheric Science)

CLOUD CHAMBER

MATERIALS

PROCEDURE
EXPERIMENT #1

  1. Barely cover the bottom of the gallon jar with water
  2. Hang the rubber glove inside the jar with the fingers down, and stretch the open end of the glove over the mouth of the jar for a tight seal.
  3. Insert your hand into the glove and pull it outward without disturbing the seal of the jar.
  4. Nothing should happen.

EXPERIMENT #2

  1. Remove the glove, drop two to three lit matches into the jar, and replace the glove for a tight seal.
  2. Pull outward on the glove once more.
  3. Fog should form inside the jar when you pull outward with the glove. The fog will disappear when the glove is snapped back.

QUESTIONS

  1. What is happening to the pressure inside the jar when the glove is pulled outward and when the glove snapped back?
  2. Why was there no smoke in the first part on the experiment?
  3. What is the purpose of the matches in the second part of the experiment?

RATIONALE

Water molecules in the form of invisible water vapor are present inside the jar. This water vapor is quickly moving around inside of the jar without sticking to each other. When the glove is pulled outward the air is expanding inside of the jar and thermal energy is lost. This causes the tiny water molecules to slow down and stick to each other. These water molecules bunch together more easily when there are solid particles to act as a nucleus, such as smoke, dust or other particles in the air. When the glove is pushed back into the jar the pressure is increased and the air is warmed causing the tiny droplets to evaporate.

In the atmosphere, air expands and releases heat as it rises to regions of lower pressure. As heat is lost, the air cools and condenses on dust and smoke particles which provide nuclei to help the water condense.

Meteorologist consider a falling barometer(low pressure) to be a sign of approaching storms, while a rising barometer (high pressure) is a sign of clear weather. The temperature at which the water droplets begin to form is called the dew point.

*This experiment was taken from The Exploratorium "Science Snackbook."

APPLICATION

Changing weather patterns, falling and rising barometer, relation of temperature and pressure.

FLINKERS

SUBJECT AREA: (Physics, General Science)

CONCEPTS: (Scientific Experimentation, Observation)

MATERIALS:

  1. A 2-liter plastic pop bottle with cap
  2. Plastic disposable pipette or a glass pipette with rubber bulb (If plastic pipettes are used they must be modified slightly. The ends of the pipette need to be cut off about an inch from the bulb. The 1/4 nut is then placed on the end of the pipette, to give it the added weight needed.)
  3. 1/4 inch hex nuts (if plastic pipettes are used)
  4. Water (enough to fill the pop bottle and then some)

OBJECTIVE: Flinking can be used in different ways to discuss the properties of density and mass. The construction of the flinker remains the same for both activities, but the goal for each is different. In the first, try and fill the bottle and the dropper with the correct amounts of water to enable the dropper to sink when pressure is applied to the pop bottle and rise when that pressure is removed. In the second activity, the dropper is to be filled with just the right amount of water that enables it to neither rise or sink, but float suspended in the water. After this activity, talk with students and define the terms density, volume, compression, mass, and pressure in very simple terms. Have the students define these terms both verbally and graphically.

PROCEDURE:

  1. Fill the pop bottle with water and place the dropper inside. More or less water in the dropper will make it sink or float. Cap the bottle and try the flinker by squeezing the bottle. If there is not enough water in the pipette, it will not sink, if there is too much water, the pipette will sink to the bottom. Just the right amount of water allows the pipette sink when the bottle is squeezed and float when it is released.
  2. To add depth to this activity, have students try their flinker in distilled, drinking, soft, and salt water.

QUESTIONS:

  1. What made the dropper sink? float?
  2. What did the water level inside the dropper do when it moved down? up?
  3. Did the air inside the dropper increase or decrease in volume during the diving? During the floating?
  4. Is water or air more compressible? Which has the greater density?
  5. What is the difference in floating/sinking in different types of water? Why?

RATIONALE: By putting pressure on the bottle the air inside the dropper gets compressed, the water level rises and thus the whole dropper becomes heavier and sinks. By releasing the pressure, the water is pushed out of the dropper again, the dropper becomes lighter, and floats.

APPLICATION: This principle is applied to submarines, where water is pumped in to submerge or pumped out to surface.

SUBJECT AREA: Physics

CONCEPTS: Centripetal forces, centrifugation, potential and kinetic energy.

WILL YOU BE WET OR DRY?

MATERIALS:

PROCEDURE: Simply fix the string to the bucket so that you can hold the bucket at the end of the string and so that you can fill the bucket up about half way with water. When you have filled up the bucket with the desired amount of water. Swing the bucket back and forth some, until you are ready to try and swing it around so that the bucket is upside down during each revolution. Imagine that you are a cowboy trying to rope a stray cow with a lasso. It works best to keep the string and bucket swinging at a 90 degree angle to the floor.

QUESTIONS:

  1. Why did the water not fall/stay in the bucket?
  2. Does it matter how fast I spin the bucket?
  3. Does it matter how long the string is?
  4. Does it matter how much water is in the bucket?
  5. Does the bucket overcome the force of gravity?

RATIONALE: This is a simple demonstration of centripetal force. The water, when it is set in circular motion, tends to want to move in a line tangent to that of its circular pathway. It pushes with a force outward into the bottom of the bucket. The bucket, however, acts an opposing force to the water, and holds it in place. If there were no bucket, the water would simple splash out in a line tangent to its starting point. Also, a certain velocity must be achieved, in order to overcome the force of gravity at the apex of the swing motion.

APPLICATIONS: Laboratory centrifuges/Roller Coasters

A Piercing Experience

"You'll get the point"

A Lesson adapted from Operation Chemistry, sponsored by the American Chemical Society.

Written by: David T. Crowther

Title: A Piercing Experience: You'll get the point."

Grade: 2-12

Outcome: The students will be able to identify and understand the concept of polymers as chains of molecules by role playing chains of molecules and through piercing a balloon with a bamboo skewer.

Proficiencies:

  1. Identify and explain monomers and polymers as molecules and chains of molecules respectively.
  2. Explain the polymer structure of a balloon in general terms (eg.. plate of spaghetti).
  3. Understand and illustrate that there is space between molecules.
  4. Hypothesize and relate other polymer substances.

Safety: Caution the students that the bamboo skewers are sharp and could cause bodily harm if pointed at or jabbed into another person either on purpose or by accident. Discourage any movement around the room holding skewers.

Materials:

  1. A 10 or 12 inch balloon for each participant.
  2. A bamboo skewer 10 -12 inches long. (Usually the smaller Shishkabob skewers work well and are available at any grocery store)
  3. A large bottle of cooking oil.
  4. a 3 ounce cup for every five people. (the cups are for the oil)

Description:

  1. Teacher holds up a balloon and a bamboo skewer and asks the class what is going to happen when the skewer is pushed into the balloon. (This is a partially inflated 12 inch balloon inflated to about 6 inches)
  2. Dip the skewer into the oil and gently twist and push the skewer through the thick nipple end of the balloon. Continue to gently twist and push the skewer until it penetrates the surface of the balloon.
  3. Continue to gently twist and push the skewer through the balloon until it starts to poke out through the area around the knot. Continue to gently twist and push until the skewer penetrates the knot end of the balloon.
  4. Ask the students if this is what they thought that the balloon and skewer would do.
  5. Allow each student to try this activity until they are successful. (note: you might have to tell them where to pierce the balloon to be most successful). Try to set a new record of skewers through the balloon. The record is seven!!
  6. Once all students have successfully pierced the balloon initiate a conversation about why this phenomenon occurred. (refer to background knowledge below).
  7. To illustrate that polymers are chains of molecules - group the students into chains of 7 - 10 by holding hands. Allow each chain to freely move around the room. Note that the beginning and end of each chain has a free "hand." another chain (Ideally in the middle of another chain). This simulates the polymer chains all hooked together to form a surface. This is easily explained by comparing it to a plate of spaghetti.
  8. Explain to the students that they are on the molecular level and that they are extremely small. Then using your finger pointing out of the top of your head role play a bamboo skewer and use the spaces between the chains to pierce the balloon all of the way through.
  9. Conclude the role play by pretending your skewer breaks one of the polymer chains - POP!!

Possible Assessment/extension: Have the students go home and find another polymer surface or container that they could also pierce with a sharp object without the object leaking (while the sharp object remains in the surface or container)

Possible suggestion: A ZipLock bag full of water.

Background information:

"It is possible to punch a bamboo skewer through an inflated balloon without popping it if one first considers the properties of the balloon. Balloons are made out of thin sheets of rubber latex which in turn are made from many long intertwined strands of polymer molecules. The rubber is stretchy because of the elasticity of the polymer chains. When the balloon is blown up, the polymer strands are stretched. The middle area of the balloon stretches more than the tied end and the nipple end (opposite the tie). A sharp, lubricated point can be pushed through the strands at the tie and nipple ends because the polymer strands will stretch around it. A sharp, lubricated point pushed through the strands at the side of the balloon will (usually) pop the balloon because the strands are already stretched and will break. Once a tear begins, it enlarges as the air rushes out of the balloon." (1994, American Chemical Society, Operation Chemistry, Polymers Unit p.4)

SUBJECT AREA (Electricity and Magnetism)

LENZ Law

MATERIALS

PROCEDURE

  1. Hold the plastic tube vertically and drop the magnet down the plastic tubing having the students keep track of the time it takes for the magnet to travel through the tube.
  2. Next, show the students that the magnet does not visibly react to the outside of the copper, aluminum, or brass tubing.
  3. Hold the copper, aluminum, or brass tubing vertically and drop the magnet down the tube. Have the students keep track of the time it takes for the magnet to travel down the tube. ( I like to start with the plastic tubing and work my way up to the thick copper pipe.)
  4. Last, drop a non-magnetic object down the copper, aluminum, or brass tubing. Have the students keep track of the time it takes for the non-metalic object to fall through the tube.

OTHER SUGGESTIONS

  1. Experiment with tubing of different thickness and diameter. How will this affect the time it takes for the magnet to travel through the tube. Try overlappping tubes of varying diameter.
  2. As an alternative to metal tubing, you may also use 2 flat pieces of aluminum with cardboard spacers for the magnet to travel between. This device can be held together with heavy duty ruber bands.

QUESTIONS

  1. What happens to the magnet as it travels through the copper, alluminum, brass, and plastic pipes? How does the magnets rate of travel differ with the different materials, diameters, and thicknesses of pipe?
  2. Are the magnets attracted to the outside of the copper, alluminum, brass, or plastic tubing?
  3. Is there a visible interaction between the foil and the magnet.

RATIONALE As the magnet falls through the tube the magnetic field around it is constantly changing. The changing magnetic field induces the flow of eddy currents through the copper, aluminum, and brass tubing. The eddy currents have a magnetic field of their own which opposes the fall of the magnet. This causes the magnet to fall more slowly.

APPLICATION

  1. Eddy currents are generated from transformers and often lead to power losses. This is prevented by using insulating glue between the thin strips of the transformer.
  2. Eddy currents are also used to reduce oscillations in many mechanical balances.

*This experiment was taken from The Exploratorium "Science Snackbook."

Subject Area -Physics

Concepts - Gravity/Acceleration/Freefall

THE SOUND OF GRAVITY

Materials

  1. Two sets of seven splitshot fishing weights.
  2. Two, 250 cm strong thin threads (monofilament fishing line).
  3. Two metal cookie sheets.

Procedure

  1. Tape one end of the fishing line to the cookie sheet and fasten the fishing weights so that the first weight is 30cm above the cookie sheet. Fasten each of the other weights so they are 30 cm from each other.
  2. Construct supports under the cookie sheet so it is a few inches off the floor (this will improve the sound produced by the falling weights).
  3. Stand on a chair and hold the line tight above the cookie sheet. Release the thread and note the rhythm of the sound as the weights hit. Note also the time interval between percussions.
  4. Clamp the seven other weights to the other thread the following distances from each other: cookie sheet to 1st weight 5 cm, the next seven: 15,25,35,45,55, &65 cm from each other respectively. *
  5. Repeat step #3.
  6. Repeat both demonstrations, alternately, several times

* At teachers discretion, one can either give the correct measurements or have the students calculate the proper measurements or find them through trial and error.

Questions

  1. What were the differences in intervals (even or increasing intervals) between the first demonstration and the second?
  2. Which of the weights had the highest velocity when hitting the cookie sheet? What was this velocity in m/s?
  3. What kind of motion is the free fall of the weights?
  4. What gives a falling object its acceleration?

Rationale The falling weights are all independently subjected to gravity. The force of gravity imparts an accelerated (ever increasing) motion to each of the weights. This acceleration is constant because of Newton's Second Law, (F=MA). Since the Force and Mass of the weights are equal, the acceleration of each of the weights is the same. The difference is that the further or "longer" the weight falls, the greater the velocity (v=at) of the weight when it hits the cookie sheet.

The distances between weights in the second demonstration were obtained from:

d=1/2 gt2 (d= distance, g= accel. of gravity, t= time)

When the weights are placed at regular intervals, the arrival is irregular, getting faster and faster (ever increasing), due to increased velocity (acceleration of gravity x time). The weights in the second demonstration also have equal increasing velocity, but because of the increased distance between weights, they arrive at even intervals.

Application A falling object increases velocity proportional to the time of fall. A high fly ball goes up and falls down with more velocity than a pop fly, but it takes longer for a high fly ball to come down because of the distance (v=dt) it travels due to an increased velocity.

Subject Area Physics Concepts

THE COLLAPSING CAN

Materials

  1. One empty aluminum can (354 ml)
  2. A Hot plate or burner
  3. Large bowl of water
  4. Tongs to hold pop can

Procedure

  1. Put about 5 ml of water in the pop can (just enough to cover the bottom).
  2. Heat the can over the hot plate or burner.
  3. Let the water boil vigorously.
  4. In a single motion, remove the pop can from the burner and INVERT it in the bowl of water.
  5. Submerge the opening to the pop can in to the water. The can will IMPLODE instantly.

Questions

  1. What was in the can besides water?
  2. What happens when water is boiled?
  3. What do you think will happen if the can is inverted in the bowl of water?
  4. What happens to the air in the can as water vapor is formed?
  5. What force is working on the outside of the can?

Rationale
Before heating, the can was filled with water and air. By boiling the water, it changes states, from liquid to gas (water vapor). The water vapor (steam) pushes the air that was inside, out of the can. By inverting the can in water, we are cooling the vapor very quickly and constraining the potential for rapid flow of air back into the can. The cooling condenses the water vapor back to water. All of the vapor which took up the interior space of the can before is now turned into a few drops of water, which take up much less space. This causes the pressure to drop and the atmospheric pressure is therefore pushing on the can and crushing it.

The total force working on the outside of the can is the total of the can's surface area in cm. multiplied by 1 kg.

Application

SUBJECT AREA General Science

HOW MUCH CO2 IN A SODA CAN?

MATERIALS:

  1. Warm 12 oz can of soda.
  2. Glass Baby Bottle
  3. Nipple for baby bottle (Hole in nipple must be closed up, this can be done via superglue).

PROCEDURE:

  1. Fill glass baby bottle with warm soda.
  2. Place nipple on baby bottle tightly.
  3. Slightly shake baby bottle.
  4. Watch nipple fill with CO2 from soda.
  5. Hold bottle upside sown demonstrating that liquid from the soda will fit inside the nipple.
  6. Slowly loosen the nipple form the bottle and watch as the nipple rockets from the bottle.

QUESTIONS:

  1. Do you know how much air you are drinking when you drink one soda?
  2. What will happen when the bottle is shaken?
  3. What will happen when I loosen the nipple from the baby bottle?

RATIONALE: The Carbon Dioxide from the soda is released via shaking of the bottle. This causes the nipple to expand because there is no where else for the CO2 to go.

Due to the pressure built up in the bottle from the CO2, when the nipple is loosened it rockets away from the bottle.

FLYING TUBE

MATERIALS:

  1. Center tube from paper towel roll
  2. 5 feet of surgical rubber tubing or "bungee" cord
  3. 3 feet of cloth ribbon (do not use slippery ribbon)
  4. 2 feet of bell or iron wire
  5. C-clamp
  6. Pliers

PROCEDURE:

  1. Fold over about 1 inch of the rubber tubing and wrap it tight with a piece wire. Twist the wire tight with the pliers and as doing so, form a loop about 1 inch in the diameter in the wire.
  2. Attach one end of the ribbon to the other end of the rubber tubing with a piece of wire. Twist the wire tight.
  3. Slip the wire loop over the screw shaft of the C-clamp. tighten the clamp to the end of a table.
  4. Lay the tube and ribbon across the table. Place the paper tube on top of the ribbon at its free end and roll it up snugly in the ribbon.
  5. While keeping the ribbon from slipping, pull the paper tube back to stretch the rubber tubing. Release the tube. The tube will be spun as the rubber tubing spins it at the same time. With enough speed and spin, the paper tube will lift off the table and may fly a loop through the air.

QUESTIONS:

  1. In what direction was the tube spinning?
  2. How is the air moving around the tube as it flies through the air?
  3. What effect does the movement of the air have on the tube?
  4. How could you make the tube turn right, left, or down?

RATIONALE: We all know that a baseball pitcher can throw a ball in such a way that it will curve off to one side of its trajectory. This is accomplished by imparting a large spin to the ball. The same is true for the tube. The thin layer of air is dragged around the spinning tube by friction. The spinning air gives a greater velocity to the air on one side of the tube creating lesser pressure on that side of the tube. Since the air pressure is then greater on one side of the tube than the other, the tube curves. This is another application of Bernoulli's principle.

APPLICATIONS: curving baseballs and tennis balls

Subject Area: General Science

MAGIC LID

Objective: To show students that atmospheric pressure is not just a downward force, but is a force acting in all directions.

Materials:

  1. 1-one gallon jar
  2. 1-glass dish large enough to cover mouth of jar

Procedure: Fill jar completly full, so the meiniscus stands high. Place glass plate on top of the jar. making sure that no air is trapped between jar and glass plate. Then quickly turn the jar upside down. It may take a couple of times to get this right, so this should be done over a sink area.

Questions:

  1. What will happen to the plate? Will it fall or stay in place?
  2. What causes the plate to stick to the jar?
  3. What conclusions can one draw from this?
  4. Is atmospheric pressure greater than water pressure?
  5. How tall would a cup have to be in order for the water pressure inside to overcome the atmospheric pressure outside?

Rationale: This is an application of atmospheric pressure. Most students think that atmospheric pressure and the force of gravity have only a downward effect, the latter is true, but atmospheric pressure exerts force in all directions. This is what allows the plate to stay attached to the jar.

Surface Tension

Subject Area: General Science

Floating Paper Clip

Objective: To show students that water has a surface tension that allows some objects to float upon the surface.

Materials:

  1. 1 paper clip
  2. A container of water
  3. 1 dinner fork
  4. Bottle of dish soap

Procedure: Start by filling container full of water. Then take paper clip and place it upon fork. Carefully place the paper clip, as level as possible on the surface of the water. This is tricky and may take several tries. Once the paper clip is floating , ask students why they believe the clip is floating. Then add one drop of dish soap and watch the clip fall to the bottom of the dish.

Questions:

  1. What causes the paper clip to float?
  2. Why does the soap cause the paper clip to fall?
  3. Could this be done with an object larger than a paper clip? If so what would it be?

Rationale: This is an example of surface tension of water. The water molecules have an attraction to each other that creates a skin like surface to the water. Adding the soap to the container disrupts this attraction and the paper clip no longer floats on the surface, but instead sinks to the bottom of the container.

Application: Water Striders (insect)

B Squared (Burning Balloons)

Robert Ruisinger

For grades 7-12 (chemistry)

Materials: One balloon filled with water, one balloon filled with air to an equal volume, and matches.

Procedure: Hold the lit match to the balloon filled with air and it will pop immediately. Next, hold the lit match to the water balloon and notice that it will not pop. It is advisable not to hold the match in one place for too long, because it may eventually pop! You may want to one before the other one, depending on your application.

Concept: The air balloon explodes immediately because the heat from the lit match quickly burns through the rubber wall. The water balloon, does not explode because the water inside absorbs the heat and disperses it throughout the volume of water. It does not let the rubber wall get to it's melting point. You can tie this demo into a lesson on heat capacities, melting points, heat absorption, conduction, etc. . Credits: South Windsor High School, South Windsor, CT 06074

Toni Orso

Subject Area: General Science (7-12)

Concepts Covered by Demonstration: Scientific Method

The Black Whole

Materials:

  1. A coffee can which is specially constructed (a slanted metal piece attached on the inside to keep water in.
  2. A glass of water

Procedure:

  1. Hold the coffee can above the observers to ensure that they can not view what is inside.
  2. Pour a glass of water directly into the coffee can. Note: do not let observers see inside to coffee can.
  3. Tip the can over on the side which will allow no water to spill out of the coffee can.

Questions:

  1. Describe exactly what you observed.
  2. Based on your observations, describe or draw what might be in the coffee can.
  3. Are you making an educated guess about what occurred?
  4. What is the scientific word for making and educated guess?
  5. How might you collect further information to support your educated guess?
  6. Write down some examples in which scientist have made educated guess about natural events that occur to try to explain what is happening in the world.

Rationale: This demonstration is an excellent way to introduce the Scientific Method because it deals with observing and recording those observations. Furthermore, the students can make an educated guess (hypothesis) about what might be occurring.

Students can also be introduced to the idea that in science there are many wonders that scientist can not fully explain. Scientist can only make observations and try to collect as much information as possible and based on the knowledge they gain from these observations they can hypothesize about what is happening. For example, scientist did not actually see the dinosaurs that lived during the Triassic Period; However, they can predict because of the evidence that was left behind in the fossil record.

It is important to inform the students that even though their educated guess about what was inside the coffee can was correct, that they would have to do millions of test to state that it was because in order for a hypothesis to become a fact or theory an enormous amount of data must be collected to support the hypothesis and millions of tests must have taken place.

Toni Orso

Subject Area: General Science (7-12)

Concepts Covered by Demonstration: Inference

Now You See It, Now You Don't

Materials:

  1. A Candle
  2. An apple
    • soak the apple in lemon juice to keep it from browning
    • carve the apple in the shape of a candle
  3. An almond
    • carve the almond in the shape of a wick

Procedure:

  1. Light the candle and give it to the audience so that they can observe it.
  2. While they are observing the candle, light the apple with the almond wick.
  3. Show the apple, almond (candle) to the audience
  4. Quickly eat the apple, almond candle (make sure you blow it out first)

Questions:

  1. What do you know about candles?
  2. Based on previous knowledge you have on candles, are the edible?
  3. Is it possible that what we already know about candles (they are not edible) could be incorrect.
  4. How do we know if candles are edible or not.
  5. Do you think that the second candle (the edible candle) is really a candle? Why or why not?
  6. In science, what is it called when we assume without actually observing it?
  7. Why did we infer that the second candle (the edible candle) was really a candle?
  8. Name 3 different example of Inference.

Rationale: This demonstration is a great tool to introduce the idea of inference. It is important for students to understand and distinguish the differences between inference and observation.

The first candle was given to the students to observe. In this instance they could easily tell that the candle was made out of wax and it was indeed a candle.

However, the second candle the students were not able to observe the candle by using all their senses. Instead they had to rely on seeing which as we know is not always reliable.

This demonstration teaches students that it is important in science to be observant and try not to make inferences.

Keeping paper dry under water

Materials: A cup, and large beaker.

Procedure: Fill large beaker with water, crumple paper and squeeze into bottom of cup. Invert cup and immerse it under water holding it as vertical as possible. Take cup back out of water, and then remove paper from bottom of the cup. have the students feel whether the paper is dry or not.

Questions:

Explanation Air is space occupying. The cup is filled with air whether it is upside down or not.This is why the water did not enter the cup.

Fission and Fusion

Materials: Soap bubble solution, two circular wire rims.

Procedure: dip two wire rims in the soap solution and blow through the wire frame. Catch the bubble on wire frame. Now stretch the bubble by pulling the frames apart until it separates into two bubbles.(fission). Press the bubbles back together until they form one large bubble again.(fusion)

Questions:

Explanation: In the case of fission, a very heavy nucleas splits and forms two medium weight nucleas. When two lightweight nuclei combine to form heavier , more stable nuclei it is called fusion.The elements that are missing in this model are the neutrons, protrons and the energy released.

Bionic Plungers

Materials: Two heavy rubber plungers(one of them with small hole in it)

Procedure: Push plungers together and pull them apart. This can be done relatively easily. Now tell students that you have bionic strength and can hold the plungers together while others try to separate them.Let students push plungers together and then cover the hole with your finger. Students will not be able to pull plungers apart and will be amazed at your bionic strength.

Questions:

Explanation: The plungers were easy to separatebecause of the hole in one of them.This allowed air to enter. By covering the hole the air was preventedfrom coming in and when the students tried to pull them apart, the volume increased between the plungers, thus decreasing the pressure. The atmospheric air pressure holding the two plungers together. The force can be calculated from the total surface area of the two circles multiplied by 1kg.

A QUICK PULL IS A BREAK FOR NEWTON

MATERIALS:

  1. light weight string
  2. 2 to 3 Kg weight with hooks on both ends
  3. roll of toilet paper

PROCEDURES:
Experiment #1

  1. suspend weight from top string with left hand
  2. pull on lower string with a quick pull with the right hand.
  3. replace string(s) and repeat pulling with a slow steady pressure.

Experiment #2

  1. hold or hang a roll of toilet paper in normal dispensing position.
  2. pull on paper with a quick pull.
  3. pull on paper with a slow steady pressure.

QUESTIONS:

  1. Do you see any difference in the way the string was pulled?
  2. Why does a slow pull on the string break it above the weight?
  3. Why does a sharp jerk break the string below the weight?
  4. Which of the two breaks makes special use of the weight's inertia?

RATIONALE: By pulling the string slowly, we are putting a strain in the string below and above the weight. Due to the mass of the weight, the strain above the weight is much larger than below. The string snaps wherever the strain is highest. When a sharp jerk is exerted on the string, the inertia of the weight keeps the strain below the weight. Although there is some strain above the weight, compared to the strain below the weight the strain in the latter is still higher, and the string snaps below the weight.

APPLICATION: tow lines; tug of war

Subject Area Chemistry, General Science

Concepts Covered by Demonstration Spontaneous Combustion

Burn Paper with Ice?

Materials:

  1. Sodium peroxide - Na2O2
  2. Finely chopped tissue paper, or sawdust, or starch.
  3. A small chip of ice.

Procedure:

  1. Before doing anything, show students a piece of tissue paper and ask: Would I be able to burn this piece of tissue paper with ice?"
  2. Tear or cut tissue paper into very fine pieces and place them in a heap on an asbestos/ tile plate, and build it up to a cone which is about 5 cm high in the center.
  3. On top of the cone, place a half teaspoon of sodium peroxide.
  4. Now show the students the small chip of ice and put it on top of the heap stand back and observe.

Questions:

  1. What reaction took place? What made the paper burn?
  2. What does the burning process need in terms of chemicals?
  3. What was the function of the sodium peroxide?
  4. Why was it necessary to divide the paper into such small pieces?
  5. What else besides paper could we use to replace the paper?
  6. What is the reaction between sodium peroxide and water.
  7. Is this reaction exothermic or endothermic?
  8. Would regular writing paper work better or worse than tissue paper? Why?

Rationale: The chip of ice at room temperature will melt and turn into water. The reaction between water and sodium peroxide is as follows:

Na2O2 + H2O ----> 2NaOH + On + energy(heat)

The oxygen released from the above reaction is in status nacendi, this means that it is in atomic form, and thus very reactive. The very reactive oxygen immediately attacks the combustible paper and sets it into flames. By slicing the paper into fine pieces, we actually decrease the kindling temperature or the activation energy needed to drive the reaction.

In place of the paper we can use fine sugar, fine coal powder, or any other highly combustible material. The reaction is very exothermic, and the released heat is enough to further decompose more of the sodium peroxide, which releases more active oxygen.

Application: Automobiles, engines, Human body(sugars)

Na2O2 + H2O ----> 2NaOH + On + energy(heat)

The oxygen released from the above reaction is in status nacendi, this means that it is in atomic form, and thus very reactive. The very reactive oxygen immediately attacks the combustible paper and sets it into flames. By slicing the paper into fine pieces, we actually decrease the kindling temperature or the activation energy needed to drive the reaction.

In place of the paper we can use fine sugar, fine coal powder, or any other highly combustible material. The reaction is very exothermic, and the released heat is enough to further decompose more of the sodium peroxide, which releases more active oxygen.

Application: Automobiles, engines, Human body(sugars)

References: Liem, Tik, L. Invitations to Science Inquiry. 1992. Science inquiry enterprises; Chino Hills, California.

Subject Area Chemistry, General Science

Concepts: Characteristics of matter, solutions, freezing and melting

Ice Cube Lifter

Materials:

Procedure:

  1. Let the ice cube float in a full cup of cold water.
  2. Show students the salt shaker and the thread and ask: "How can I lift the ice cube out of the water without getting under the cube?"
  3. Let the thread lie on the ice cube and sprinkle salt on it -- especially close to the thread.
  4. Wait a minute or so, lift the thread slowly to check whether the water above it is frozen; if so, lift both ends of the thread and lift the ice cube out of the water.

Questions:

  1. What does salt do to ice on the road in the winter time?
  2. At what temperature does ice melt?
  3. What do you think salt does to the melting point of ice?
  4. What must the melted ice above the string do in order to lift the cube?
  5. Where else do we find this principle of lowering the melting point of ice applied in daily life

Rationale: As salt water has a lower melting or freezing point than pure water, the addition of salt to the ice cube makes it melt at the places where the salt is sprinkled. This means that the ice around the thread will melt, but the temperature of this water above the ice cube is still below 0oC. When the salt dissolves in more of the melted ice, the solution gets more dilute, increasing the freezing point close to 0oC. As the water still has a temperature of a few degrees below 0oC, it freezes again. This makes it possible to lift the ice cube out of the water. When making ice cream at home, crushed ice and salt are mixed in the mantle of the ice cream maker to lower the temperature below the freezing point of water.

Application: Snow and ice removal from city streets, home made ice cream

REFERENCES References: Liem, Tik, L. Invitations to Science Inquiry. 1992. Science inquiry enterprizes; Chino Hills, California.

A HOT TONE

SUBJECT AREA: (Physics, General Science, Sound)

MATERIALS

  1. PVC drain pipe, 1.5 to 2 inches diameter, several lengths from two to five feet long.
  2. Propane torch

PROCEDURE:

  1. Light propane torch and turn on to largest (hottest) setting.
  2. Hold the torch in a position so that the flame is perpendicular.
  3. Lower the pipe over the flame. Adjust height until tone develops.
  4. Repeat with each pipe length.

QUESTIONS:

  1. How is the tone produced?
  2. Is there a difference with different lengths of pipe?

RATIONALE: The heat of the flame causes the air in the tube to suddenly expand. The hot air begins to oscillate up the tube, resulting in a resonating tone. A standing wave is created in a tube with open ends. The longer the tube, the longer the wavelengths produced in the standing wave and thus the lower the tone.

APPLICATION: Steam whistles, upward air draft on a chimney

Prepared by: Annette Hynes

Taken from: Ron Bonnstetter

Subject Area: Physics

Concepts: Density.

Magic Disappearing Balls

Materials:

  1. Three ping-pong balls
  2. Two or three metal balls about the same size as the ping pong balls
  3. A bag of pinto beans
  4. A large mixing bowl

Procedure:

  1. Pour the beans into the bowl.
  2. Bury the ping-pong balls under the beans and lay the metal balls on top.
  3. Gently shake the bowl.
  4. The metal balls will sink to the bottom and the ping-pong balls will rise to the top.

Questions:

  1. What happened to the metal balls?
  2. What happened to the ping-pong balls?
  3. Compare the densities of the three objects.
  4. What would happen if we tried a similar experiment in water by dropping the metal ballsfrom the top and and releasing the ping-pong balls from the bottom?

Rationale: The two types of balls and the beans all have different densities. The metal balls have the highest density, the ping-pong balls have the lowest density, and the pinto beans have a density somewhere in between. When you first start shaking the bowl, all the objects are free to move around. The metal balls are the densest so they sink to the bottom and the ping-pong balls are the lightest, so they "float" up. The same effect happens in water since water has a density somewhere in the middle between the metal balls and the ping-pong balls.

Application: Buoyancy of objects in water.

Chemistry

Concepts Covered from National Science Standards:

  1. Force and Motion
  2. Energy
  3. The Universe and its Happenings

THE SODA CAN CANNON

MATERIALS:

  1. Three empty soda or juice cans
  2. Two Styrofoam cups
  3. Lighter fluid
  4. A match
  5. Goggles

PROCEDURE:

  1. With a can opener, cut the tops of the cans as follows:
    Top can: open on top of can and half of the bottom removed.
    Middle can: open on both ends.
    Bottom can: only the top removed, leave bottom closed.
  2. Connect the three cans on top of each other with masking tape or duct tape
  3. Punch a hole about 2 cm in the bottom can on the side about 1/2 cm in diameter (i.e.. use a large nail).
  4. Tape the two Styrofoam cups together rim to rim and place it tightly in the top opening.
  5. Place two or three squirts of light fluid in the bottom hole and shake the stack of cans.
  6. Let the stack stand for a few minutes. You are now ready for ignition!
  7. Strike a match and hold the flame close to the bottom opening.
  8. BE CAREFUL, KEEP AWAY FROM THE CANNON BALL!

QUESTIONS:

  1. What are the two baffles in the cans for?
  2. What purpose did shacking the stack of cans have?
  3. What kind of energy resulted from the chemical explosion?
  4. What other kinds of liquids do you think could be use in place of lighter fluid?

RATIONALE: The baffles were left in the cans to enhance the mixing of the fuel with the air in the cylinder. The baffles momentarily retain and reflect the heat of the ignition to ensure combustion of the fuel. The shaking of the cylinder was done immediately after the fuel was added for exactly the same reason. The better the mixture of fuel vapors and the air, the better the explosion. The chemical energy stored in the lighter fluid is transformed by the combustion into kinetic energy of the moving cannon ball. Gasoline or alcohol may be used instead of lighter fluid.

APPLICATION: internal combustion engine; liquid fuel rockets

Prepared by: Annette Hynes

Taken from: Dale Kyser and Roger Gray, physiology teachers of Garden County High School, Oshkosh, Nebraska.

Subject Area: Physics and Physiology

Concepts: Sound, hearing, vocalization.

Eardrums

Materials:

  1. Empty coffee can
  2. Disposable latex gloves
  3. Pieces of a broken mirror (a compact mirror works really well)
  4. Glue
  5. Tape and/or rubber bands
  6. Flashlight or laser beam

Procedure:

  1. Cut both sides of the coffee can off with a can opener.
  2. Stretch the latex over one side of the can and keep it in place with the rubber bands and the tape.
  3. Break a mirror and glue one of the pieces on the outside of the latex. Usually a piece of about one square inch works well.
  4. In a dark room, have one person shine the flashlight on the mirror piece. Have the other person hold the can and yell into open end.
  5. Watch the light patterns that form on the wall. Experiment with different voices. Try different volumes, pitches, words and people.

Questions:

  1. What causes the different patterns on the wall?
  2. Why does the mirror on the latex vibrate?
  3. What happens when you change the pitch, volume, or tone of the voice being used?
  4. How is this similar to your ear drum? How about your vocal cords?

Rationale: The sound waves from the speaker's voice causes the latex to vibrate like an ear drum or a vocal cord. These vibrations change according to the pitch (how high or low the voice is), the volume, and the tone of the voice. The different kinds of vibrations show different light patterns on the wall. If you make enough of these, you could have your own musical "laser light show" in your classroom.

Application: Eardrums, vocal cords, percussion instruments.

Subject Area: (Physics)

Concepts Covered by Demonstration:

Bottle Blast

Materials: Beer bottle and water.

Procedure:

Experiment 1
Have bottle filled full of water and ask the class if you should be able to break the bottom out of it and why.
Experiment 2
Have the bottle empty and ask the class if you should be able to bread the bottom out of it and why.
Experiment 3
Have the bottle half-filled with water and ask the class if you should be able to break the bottom out of it and why.

Questions:

  1. How can I (the teacher) break the bottom out of the bottle?
  2. Why won't the bottom break out with the bottle full of water?
  3. Why won't the bottom break out with the bottle empty?
  4. What causes the bottle to break out when it was half full of water?
  5. What concepts could we talk about as a class on this demo?
  6. Why don't the sides of the bottle break instead of the bottom?

Rationale:
This is a demo that shows pressure, force and gravity. Pressure is the force exerted on a unit area of surface. Force is the push or pull measured by the acceleration it produces on a standard, isolated object. (usually measured in Newton's) Gravity is the force experienced by one unit of mass placed at that location.

This demo helps explain the concepts of every day life.

Application: Bottle and water

SUBJECT AREA General Science, Discussion of Lenses

TITANIUM DIOXIDE

MATERIALS:

  1. A large print of the TITANIUM DIOXIDE. (Must all be capital letters)
  2. A Cylinder filled with water, and closed at top so it can be turned sideways

PROCEDURE:

  1. Tell the class you have a magic cylinder and have them watch what it does.
  2. Hold the cylinder of water in front of the word TITANIUM DIOXIDE. See what happens.

QUESTIONS:

  1. Why does the Word titanium invert and the word dioxide not?
  2. Why does the Cylinder invert the words?

RATIONALE:
Both words actually convert, however when the word DIOXIDE converts it still looks the same. This is because these letters look the same when either upside down or right side up.

This can be used as a discussion of science and how a scientist has to think everything out and can not be easily teased.

This can also be used in a discussion of lenses and why the letters are converted.

Egg Blow

Materials:
Clear rubber tubing (2-3 feet, 1 in. diameter works best.), 2 raw eggs (doesn't hurt to have some extra on hand), 2 plastic garbage bags with holes for arms and head, paper towel for clean up.

Objective:
Egg Blow can be used as a fun activity involving air flow, pressure and force. Two students compete trying to blow egg yoke through the tube onto the other student. You can clue one of the students in by having them create a seal on their end of the tube with their lips. This creates a sealed container and no matter how hard the other student blows the egg yoke will not move. By using this activity and some questioning your class can discover the laws for air flow.

Procedure:

Round one: Raw egg yoke is placed in the center of the clear rubber tube. Two volunteers are called up to participate in the egg blow competition (take either volunteers or students that you feel will be good sports.) The volunteers should put on the garbage bags to protect their clothing. Have the two volunteers take opposite ends of the tube. They should hold the tube carefully in their hand so the egg yoke does not slide out of the tube. The two volunteers hold the tube to their mouth and the instructor says "Go". In the first round let the students compete normally by blowing and see who wins. Question the students about what just happened (see Questioning #1 below.)

Round two: Without telling the winner have the other volunteer create a seal at their end of the tube using their lips so no air escapes. Make sure you tell the person who is sealing the tube not to blow. Let the two students compete again, same procedure as the first. When the student who is blowing hard, trying to win his/her second straight competition stops to take a breath of air. Have the student that was sealing their end of the tube blow the egg out of the tube. Hopefully making for a good laugh.

Thank your volunteers and have the student who sealed the tube describe what they did.

Questioning:

  1. Have the students describe what happened in the first round of Egg Blow in terms of force and pressure. Why did the egg come out of the end it did?
  2. Have the students describe what happened in the second round of Egg Blow in terms of force, pressure, and air flow. Why didn't the same thing that happened in round one happen in round two?

Explanation: In the first round of Egg Blow the egg yoke goes to the end of the tube of lesser force. In the second round when one end of the tube is sealed the reason for the egg yoke not moving is air flow in equals air flow out. Since no air flow is able to move out of the tube, the air being blown at the opposite end of the tube is not able to apply a force to the egg yoke. Because there is no air flow out, no matter how hard you blow it has no effect on the egg yoke.

Prepared by: Annette Hynes

Taken from: Observations made on my college friends in the residence hall cafeteria.

Subject Area: Chemistry & Physics (a little biology could also be thrown in).

Concepts: Solubility and solutions.

Cafeteria Coke Joke

Materials:

  1. One can of sodapop.
  2. A glass container (cafeteria glass, beaker, or erlenmeyer flask).
  3. Table salt.
  4. Teaspoon
  5. Basin (to catch the overflow)

Procedure:

  1. Pour the soda into the glass. Try to tip the glass and pour along the side so that the pop doesn't fizz too much.
  2. Pour about one teaspoon (or more, if you like) of salt into the spoon.
  3. Dump the salt into the soda.
  4. Watch the fizz rise!

Questions:

  1. How soluble is salt in water?
  2. How soluble is gas in water?
  3. What happens to the salt when you dump it in the sodapop?
  4. What happens to the gas when you dump the salt in the sodapop?
  5. Why does the gas dissolve out of the sodapop?
  6. How can you apply what you just learned about the solubility of gas in water to aquatic and marine animals? What happens to a fish (or a SCUBA diver) if it moves from a deep area to the surface too quickly?

Rationale:
Salt is very soluble in water. Air dissolves in water, but not very well, especially compared to salt. In a solution, the solvent (the water in this case) can only hold so much solute (stuff like salt, sugar, air, etc.) . When the salt is added to the water, the water can't hold as much dissolved air in it, so the air escapes and we see the fizz.

Another way to say this is that the solubility of the gas is decreased. The things that affect the solubility of gas in water include temperature, pressure, and the amount of stuff already dissolved in the solution. A cod fish (or a SCUBA diver) swimming deep in the ocean is under a lot of pressure. If a fisher catches the fish and pulls it up quickly, the pressure that the fish is under decreases. Then not as much air can be dissolved in the blood of the fish. The gas in the blood dissolves out, and the fish has a bloated swim bladder and its tummy will be puffed up. Quick changes like this can kill a fish or a diver.

Application: SCUBA gear, physiology of marine and aquatic animals, storing sodapop.

PHYSICS

THE BERNOULLI POP CAN GHOST

MATERIALS:

  1. Two empty soft drink cans.
  2. About two dozen straight drinking straws.

PROCEDURE:

  1. Spread the straws parallel to each other on the table and leave about 1/2 to 1 cm gap in between them.
  2. Place the two cans upright about 2 cn from each other on the straws and show the students that they can easily move closer or further apart.
  3. Blow in between the two cans with a short hard puff.
  4. Now spread the two cans about 5 cm apart. Blow harder.
  5. Now place the cans about 20 cm apart. Take a deep breath and blow a constant stream of air on the RIGHT SIDE of the LEFT can and move your head towards the right, while constantly blowing.

RATIONALE:
This demonstration illustrated the Bernoulli principle. As the speed of air increases, the air pressure decreases. Blowing in between the cans created a flow of air and thus a lower pressure compared to the stationary air on the other side of the cans. It is this lower pressure that drew them together.

Theoretically, the cans could be placed an infinite distance away from each other and still be drawn together, as long as a constant flow of air on one side of one can moves along with it, to move it to the other can. Indeed, the faster the flow of air, the lower the pressure it exerts. But for the cans that were placed 20 cm apart, only a constant flow that could move the can, was necessary.

APPLICATION: Aviation ( ie. airplane wings)

Chemistry

CONCEPTS COVERED BY DEMONSTRATION Melting Points

ICE CUBE LIFT

MATERIALS:

  1. Ice cube floating in a cup of cold water.
  2. Piece of thread or string Salt shaker

PROCEDURE:

  1. Float the ice cube in the glass.
  2. Show the audience the salt shaker and thread.
  3. Dip the thread in the water, lay it over the ice cube and shake salt on it.
  4. Wait a minute or so, lift the the thread slowly out of the water and the ice cube will be frozen to it.

QUESTIONS:

  1. What does salt do to ice on roads in the winter?
  2. At what temperature does ice melt?
  3. What do you think salt does to the melting point of ice?
  4. What must the melted ice above the string do in order to lift the cube?
  5. Where else do we find this principle of lowering the melting point of ice applied in daily life?

RATIONALE: As salt has a lower melting point or freezing point than pure water, the addition of salt to the ice cube makes it melt at the places where the salt is sprinkled. This means that the ice around the thread will melt, but the temperature of this water above the ice cube is still below zero degrees C. When the salt dissolves in more of the melted ice, the solution gets more dilute, increasing the freezing point close to zero degrees C. As this water still has a temperature of a few degrees below zero degrees C, it freezes again. This makes it possible to lift the ice cube out of the water. When making ice cream at home, crushed ice and salt are mixed in the ice cream maker to lower the temperature below the freezing point of water.

APPLICATION:

Taken from Mr. Wizard's Supermarket Science

Chemistry

CONCEPTS COVERED BY DEMONSTRATION

EGG DROP

MATERIALS:

  1. 1 hard boiled egg (w/o shell)
  2. 8oz. glass nursing bottle or flask
  3. Accordion folded 4x4in piece of paper
  4. matches

PROCEDURE:

  1. Light the piece of paper on fire.
  2. Quickly drop the paper into the bottle and immediately place the egg over the opening.
  3. The egg should drop into the bottle. Now to get it out, rinse the bottle out with water.
  4. Turn the bottle upside down so the egg drops into the mouth of the bottle. Blow as hard as you can into the bottle. When you stop blowing, the egg will drop out!

QUESTIONS:

  1. Why does the egg drop into the bottle?
  2. What happens to gases as they are heated?
  3. What is a vacuum?
  4. What element is required by fire?

RATIONALE
As the paper in the bottle burns, the gases inside the bottle are heated and expand. (These gases are both air and the gases produced by the burning of the paper). The pressure inside the bottle increases causing some of the gases to be forced out past the egg. This acts as a one-way valve. When the flame burns out, the gases contract which in turn causes a vacuum to pull the egg into the bottle.

APPLICATION

Taken from Mr. Wizard's Supermarket Science

Presented by Cindy Larson-Miller

Borrowed from Newton's Apple

Subject Area: Physical Science, Earth Science

Concepts Covered: Air pressure, weather phenomena

Pop Bottle Barometer

Materials:

Procedure:

  1. Turn the empty pop bottle upside down into the measuring cup containing the colored water. Make sure the bottle fits tight into the cup so that the lip of the bottle does not touch the bottom of the glass.
  2. Mark a line on the cup to indicate the water level within the pop bottle.
  3. Reexamine the water level as the weather changes.

Questions:

  1. Did the water level change with the changing temperature?
  2. What is inside the bottle?
  3. What force is acting on the water?
  4. What causes the water level in the bottle to rise?
  5. Why is dry air heavier than moist air?

Rationale:
The amount of air within the bottle is fixed at whatever the atmospheric pressure was on the day you turned the bottle upside down. The pressure on the surface of the water depends on the current air pressure. As the weather becomes drier, the air pressure increases, forcing the water to rise in the bottle.

Application: To be added by user

Presented by Cindy Larson-Miller

Borrowed from Newton's Apple

Subject Area: Physical Science, Chemistry

Concepts Covered: Surface tension

Something's Fishy

Materials:

Procedure:

  1. Trace a picture of a fish on a piece of paper and cut it out. Cut a small hole in the center of the fish.
  2. Place the paper fish in the pan of water.
  3. Drop a tiny amount of oil or detergent into the hole in the fish.

Questions:

  1. Ask the students to predict what will happen.
  2. What happened?
  3. Why doesn't the fish move at first?
  4. Why does the fish move after the oil is placed on it?
  5. What is surface tension?
  6. Is the surface tension of the water increased or decreased by the oil?
  7. Which has a greater surface tension, the water or the oil?

Rationale:
All liquids have a certain amount of surface tension, a property that causes a liquid surface to behave like an elastic skin. The vegetable oil or detergent decreases the water's surface tension. If different parts of the fish have contact with different surface tensions, the fish will be propelled.

Application: To be added by user

Presented by Cindy Larson-Miller

Borrowed from Newton's Apple

Subject Area: Biology, Health

Concepts Covered: Osmosis, nutrition

Soaking Spuds

Materials:

  1. A small potato sliced into several flat pieces
  2. Two small bowls
  3. Table Salt

Procedure

  1. Place some pieces of the potato in one bowl and the rest in the other.
  2. Fill both bowls with water. Add two tablespoons of salt to one and label it "salt water".
  3. Let the potatoes soak for 15 minutes and compare.

Questions:

  1. Is there a difference in the firmness of the potatoes? Why?
  2. Is there a change in the amount of water in the potatoes?
  3. Where did the water go? Why?
  4. What is osmosis?

Rationale:
Through osmosis, water moves from areas of low salt concentration to areas of high salt concentrations. Adding salt to the water creates a higher salt concentration in the dish than in the potato. Consequently, water in a potato that is soaking in salt water migrates out, leaving behind a limp spud.

Application: To be added by user

Presented by Cindy Larson-Miller

Borrowed from Saturday Science Activities

Subject Area: Physical Science, Health

Concepts Covered: Air pressure, food content

Swelling Syringes

Materials: A clean, empty plastic syringe and several marshmallows

Procedure:

  1. Place the marshmallows in the barrel of the syringe.
  2. Cover the tip of the syringe with your finger during the demo.
  3. Pull the syringe back and watch what happens to the marshmallow.
  4. Plunge the syringe forward and watch what happens to the marshmallow.

Questions:

  1. Ask the students to predict what will happen to the marshmallow.
  2. Is there a change in the size of the marshmallow? Why?
  3. What does this mean about the content of the marshmallow?
  4. What is being compressed, the air or the marshmallow?

Rationale:
As you pull back the plunger on the syringe, you are decreasing the air pressure in the barrel of the syringe by allowing the air molecules more space to move around in. The air in the marshmallow "pushes" out and causes it to expand. The opposite happens when you push in on the plunger. As the air pressure increases the marshmallow is compressed.

Application: To be added by user

Subject Area (Physics, Chemistry, Biology, Earth Science, General Science)

Concepts Cover by Demonstration. (taken from National Standards and Frameworks) (list as many as apply)

THE HOOVER BUGLE

MATERIALS: corrugated plastic tube

  1. swimming pool drain hose or vacuum cleaner hose
  2. 6 feet long, 4 cm diameter

PROCEDURE:
Experiment #1:

  1. holding the plastic tube in one hand at one end, swing it above your head using only the wrist.
  2. swing slowly at first, then slowly increase the rate faster and faster, then slow down again.
  3. try to vary the speeds to imitate the sound of a bugle

Experiment #2:

  1. tear a piece of paper up into small pieces
  2. place the pieces in a pile on the edge of a table.
  3. with one hand, hold one end of the tube just above the paper and with the other hand swing the other end above your head.

QUESTIONS:

  1. How was the sound produced?
  2. How did the pitch change with increase in speed?
  3. Why did the pitch skip an interval each time it changed?
  4. What is the next higher pitch called?
  5. Which way is the air flowing in the tube?
  6. What caused the pieces of paper to move?
  7. Which experiment could be performed using a smooth walled tube?

Rationale:
This is an application of Bernoulli's principle. As the free end of the tube passes through the air, the air pressure within the tube is reduced. Air flows through the tube from the fixed end to the moving end. The papers move due to the air moving into the fixed end of the tube.

As the air moves through the tube, it begins to oscillate due to the corrugations of the tube. The corrugations determine the frequency of the oscillations and thus the tone produced. At slower speeds the oscillations are slower (lower frequency) and a basic low tone is heard. As the tube moves faster, the air moves faster with the production of ovetones (harmonics). The next tone heard will be at a frequency twice the original, or one octave higher, but only when the tube reaches a certain velocity. No intermediate tones are heard at intermediate velocities. Higher harmonic tones can be produced by increasing the rate of rotation. The sound will resemble that of a bugle. The quality of the tone is dependent upon the number of corrugations per inch and the pitch dependent upon the length of the tube. Visit the vacuum cleaner section of your local department store and try out several different tubes to find one that you like.

APPLICATION: Pop Bottle Whistles; Oriental flutes

Seeing the Light: An AC Experience

SUBJECT AREA: (Physics, Physical Science)

CONCEPTS COVERED BY DEMO.: AC Current, Color wheel

MATERIALS:

First Example:

  1. 12.6 Volt AC 1.2 AMP Power Transformer (Radio Shack Cat. No. 273-1452)
  2. Two 220 - 400 OHM Resistors (1/2 Watt)
  3. AC Line Cord (6 foot) (Radio Shack Cat. No. 278-1255)
  4. LED (Diffused Bi-Color (Red/Green) .200 Diameter (pack of three were bought for $1.50 from JIM-PAK Electronic components)
  5. 4 to 6 foot of output electrical cord to run from the transformer to the resistors and LED

Second Example:

  1. AC Adapter Input: 120V 60 Hz 5.5 VA
    Output: AC 6V 500mA
    (Comment: This was just an adapter found around the house)
  2. Two 220 - 440 OHM Resistors (1/2 Watt)
  3. LED (Diffused Bi-Color (Red/Green) .200 Diameter

ASSEMBLY MATERIALS: