Liquid Nitrogen
A little fun with liquid nitrogen, at -320°F.
"Heatstroke" experiment
We know that an object that is hotter than its environment will naturally cool down as it transfers thermal energy by conduction, convection and radiation. But how is the process of heat transfer affected by evaporation of a liquid? In the video at right, students test this by comparing 4 pop cans filled with very hot water. Two cans are wrapped in wet paper towel (one of these placed in front of a fan); and two more cans have no paper towel (one of these placed in front of the fan). The can with the wet paper towel, placed in front of the fan, cooled off the most: evaporation reduces temperature significantly!
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"Hot Bolts" experiment
As we are exploring ways that thermal energy can transfer, we conducted a lab activity to measure whether heat transfer is affected by "amount" of matter, and by "type" of matter. We heated a collection of metal bolts to 100°C, then placed the bolts in cups of water or cooking oil. Students measured the temperature change of the liquid after one minute. Our findings indicated that increasing the number of bolts increases the temperature change; and that oil heats up faster and hotter than the same amount of water.
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Food Dye and Thermal Energy
How does thermal energy affect the movement of water molecules? We placed a drop of food coloring in water at three different temperatures. We found that the hotter the water, the faster the food dye mixes with the water, due to the increased kinetic energy of the molecules (faster movement and more collisions)
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Burning Steel Wool
You can ignite steel wool by touching it to the electrodes of a 9-volt battery. Oxygen is able to assist the burning, and in a short time the entire piece of steel wool is "oxidized"- which means it has turned to rust (iron oxide). Despite the sparks and smoke that come out of the steel wool, the mass actually INCREASES during the process, due to the added oxygen. We were able to measure a gain of mass of approximately 2 grams.
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Static Electricity
What happens when you acquire a strong electric charge from a Van de Graaf generator? The generator produces a positive charge. When you touch it, the charge spreads to the surface of your body. This causes every hair to repel from every other hair. Under the right conditions, the result can be quite dramatic!
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Bowling Ball Pendulum Demonstration
The famous bowling ball demonstration illustrates the Law of Conservation of Energy. This law of physics states that energy can never be created or destroyed; it can only change to another form, or transfer from one object to another. The young scientists in this video pull the bowling ball back until it is against their nose. They let the ball swing away and come back, KNOWING that the laws of physics tell us the ball can NEVER return to its starting point- because some of the beginning potential energy is converted to friction as the ball pushes through the air. But do they BELIEVE what they know to be true? Our mind tells us the ball can't hit us; our eyes say . . . LOOK OUT, HERE IT COMES!!!
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Thermite Reaction
We learned that friction between two objects causes an increase in thermal energy (heat). When two solid steel spheres strike each other sharply, the friction- and heat- are focused in a very small area. In this demonstration, the two steel spheres are rusty; and one is coated with a layer of aluminum foil. As a result, the mixture of rust (iron oxide) and aluminum, heated to a high temperature at the point of impact, briefly results in a chemical reaction called a thermite reaction. The reaction of iron oxide and aluminum is capable of reaching about 5,000°F, and is able to melt iron. This reaction is often used to melt the rails of railroad tracks, in order to smoothly join sections of rail. Of course our demonstration just produces a shower of sparks!
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Creating Electromagnets from Copper or Aluminum Tubes
In Science we are exploring Michael Faraday's discovery that an electric current can be generated by moving a magnet near a conductor. This is how most of our electricity is created in rotating generators which are driven by wind, water or steam.
One way to demonstrate this science principle is to drop a powerful magnet down a metal tube, such as a copper pipe or a roll of aluminum foil. As gravity pulls the magnet down the tube, a current is generated in the tube. This turns the tube into an electromagnet- which repels the falling magnet! Therefore, the magnet falls much more slowly than expected, which was very puzzling to students, as seen in the video. Here is link to a Youtube video explaining the science behind this example of crazy-but-true science. To quote Michael Faraday: "Nothing is too wonderful to be true, if it be consistent with the laws of nature!" |
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Acid Breath?In the video at right, two students are blowing through straws into bottles of water. The carbon dioxide bubbling through the water creates weak carbonic acid. The water bottles contain an acid indicator solution (phenol red), which gradually turns yellow as the water becomes more acidic.
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Fireballs Experiment
Some common powders will burn when hot enough, but only if the particles receive enough oxygen. This can be achieved by blowing the powder out of a tube, and through the flame. In the video at right, we found that powders made from organic materials (plants or animals) will burn. These include flour, corn starch, sugar, non-dairy creamer, and lycopodium. Powders from mineral sources did not burn because they lack the carbon and hydrogen atoms that can easily combine with oxygen. These non-burning powders included salt, borax, and baking soda.
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What is an Electric Generator?
Students tested some simple generators to explore how electricity is produced. It seems that spinning magnets, placed near coils of copper wire, create an electric current in the wire. But how? What is electric current exactly? There is much to learn about this form of energy that is so important to our technological lives!
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Gum Chewing Experiment
Question: What is the effect of chewing on the mass of a piece of gum?
We discovered that a typical chunk of bubble gum in the wrapper has a mass of about 8 grams. After chewing the gum for 10 minutes, the mass is reduced to about 2-3 grams. What was the missing matter? To the right is a clip showing the ingredients in a piece of "Bubblicious" gum. Can you figure out what "disappeared" during the first minutes of chewing? |
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Testing Elasticity of GumBubble gum is really just a chunk of soft latex rubber, packed with sugar and a bit of artificial flavoring. Once you get that pesky sugar out of the way, the texture is conducive to stretching , as these students demonstrate. The remaining latex takes a very long time to break down, unless mixed with peanut oil, which rapidly dissolves it! That's why you don't want to chew a piece of gum right after eating a peanut butter sandwich. (Or do you?)
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Calculating Density of ObjectsDensity is calculating by dividing an object's mass by its volume (grams ÷ milliliters). Water has a density of 1.00, which means 1 milliliter of water weighs exactly 1 gram (1 ÷ 1 = 1.00)
So what would happen if an object had a density of 2.00 g/mL, and you placed it in water? What about an object with density of 0.50 g/mL? What about an object with a density of 1.01? |
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How Do Fish Control Their Depth?Meet Bruce, my pet shark. He suffers from hydrophobia (fear of water), so I occasionally let him swim around the classroom, as long as he doesn't eat the children. Bruce is able to "swim" in the atmosphere, because his density has been carefully adjusted to match the density of air in my classroom. Real fish control their swimming depth using their "swim bladder". This is a small air sac inside the fish. When a fish wants to swim closer to the surface, it takes some of the air collected through its gills, and sends it to the swim bladder. Want to swim deeper? Just "pass a little gas" out of the air sac to increase density- and down you go!
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Penny Drop ExperimentHow many drops of water can sit on a penny? How is the result affected by adding soap to the penny first?
Students discovered that water has a remarkable property called "cohesion". That means that water molecules are attracted to each other like magnets. Cohesion allows the molecules to pile up in a dome shape on the penny, resisting the force of gravity. Soap is a kind of chemical called "surfactant". That means it weakens the attraction between water molecules, resulting in fewer drops of water on the penny. |
Bald-faced Hornet NestMiles and Sarah were wondering what's on the inside of an old (dead) hornet nest. We cut a window in one side, and found lots of dead hornets, some that never hatched at all, and one that was actually climbing out of its cubby-hole when it died! Pretty cool.
(P.S. Don't try this on a nest with living hornets!!!) |