In the traditional version of the Egg in the Bottle Experiment, the burning piece of paper heats the molecules of air in the bottle and causes the molecules to move far away from each other. Some of the heated molecules actually escape out past the egg that is resting on the mouth of the bottle (that’s why the egg wiggles on top of the bottle). When the flame goes out, the molecules of air in the bottle cool down and move closer together. This is what scientists refer to as a partial vacuum. Normally the air outside the bottle would come rushing in to fill the bottle. However, that darn egg is in the way! The “push” or pressure of the air molecules outside the bottle is so great that it literally pushes the egg into the bottle.
In the Upside-Down Twist, the science is the same as the traditional Egg in the Bottle trick, but the whole thing is just inverted. It's a nice twist on a classic science demonstration.
The secret to making the ink disappear is carbon dioxide in the air which reacts with the water in the solution to form carbonic acid. The carbonic acid then reacts with the sodium hydroxide in a neutralization reaction to form sodium carbonate. This lowers the pH of the solution with the alcohol acting as an acid to turn the indicator colorless and the ink stain magically disappears. The "fading time" can be prolonged by adding a small amount (use drops to make these adjustments) of sodium hydroxide. But care should be taken not to add too much sodium hydroxide. Here's a fun fact... red disappearing ink can be made using phenolphthalein (a very common acid-base indicator) in place of thymolphthalein.
If you dip a piece of the screen (the mesh bag) into a glass of water, you notice that the water fills the screen holes. A force called cohesion, which is the attraction of molecules that are the same to each other, causes this effect. The surface tension “membrane” is always trying to contract, which explains why falling droplets of water are spherical or ball shaped. The water stays in the bottle even though the card is removed because the molecules of water are joined together to form a thin membrane between each opening in the screen. Tipping the bottle or touching the screen will break the surface tension and surprise everyone with a gush of water!
How are Pop Rocks made? According to information from the manufacturer, Pop Rocks start like any other hard candy by combining sugar, lactose (milk sugar), corn syrup, and flavoring. These ingredients are heated to the boiling point and the hot sugar mixture is mixed with carbon dioxide gas under high pressure (about 600 pounds per square inch). The process causes tiny high pressure bubbles of carbon dioxide gas to form in the candy.
When the hot candy mixture cools and the pressure of the gas is released, the hard candy shatters into tiny pieces of carbonated candy. If you look carefully at the candy under a magnifying glass, you'll see the tiny bubbles - each containing a small amount of carbon dioxide gas under high pressure (600 PSI). When the candy melts in your mouth, the 600 PSI bubbles of gas are released with a loud popping sound. Very cool!
In the experiment with the balloon, mixing Pop Rocks with soda is a physical reaction - not a chemical reaction. The soda dissolves the candy and releases the small bubble of carbon dioxide gas from the Pop Rock. Believe it or not, most of the carbon dioxide in the balloon came from the soda. Dropping Pop Rocks into soda causes some of the carbon dioxide from the soda to escape. That's the real reason why the balloon inflates.
So, will you explode if you eat Pop Rocks and drink soda? No... but you might get a pretty nice burp out of the deal.
What does the salt do? Just like we use salt on icy roads in the winter, salt mixed with ice in this case also causes the ice to melt. When salt comes into contact with ice, the freezing point of the ice is lowered. The lowering of the freezing point depends on the amount of salt added. The more salt added, the lower the temperature will be before the salt-water solution freezes. For example, water will normally freeze at 32 degrees F. A 10% salt solution freezes at 20 degrees F, and a 20% solution freezes at 2 degrees F. When salt is added to the ice, some of the ice melts because the freezing point is lowered.
Always remember that heat must be absorbed by the ice for it to melt. The heat that causes the melting comes from the surroundings (the warmer cream mixture). By lowering the temperature at which ice is frozen, you were able to create an environment in which the cream mixture could freeze at a temperature below 32 degrees F into ice cream.
The secret is inside the straw - it's air! Placing your thumb over the end of the straw traps the air inside. When you trap the air inside the straw, the air molecules compress and give the straw strength, which in turn keeps the sides from bending as you jam the straw through the potato. The trapped, compressed air makes the straw strong enough to cut through the skin, pass through the potato, and exit out the other side. Without your thumb covering the hole, the air is simply pushed out of the straw and the straw crumples and breaks as it hits the hard potato surface.
Be sure to keep your fingers out of the way. After you stab with the straw, take a look at the end that passed through the potato. There's a plug-o'-spud inside the straw. If you should have a finger or thumb or hand in the way of the straw as it collides with the potato, then there will be a plug-o'-you in the straw, too. Ouch!
When you mixed the borax in with the water, you created a suspension. A suspension is a mixture that contains solid particles large enough to settle out. By mixing the borax into hot water, instead of room temperature or cold water, the borax stays suspended longer within the water.
As the borax begins to settle out, or sediment, it begins to crystallize. You'll see this crystallization on both the bottom of the jar and, you got it, on your snowflake. The borax continues to sediment on top of the snowflake and on top of other borax crystals until you pull it out of the water the next morning.
The trick behind the Disappearing Money experiment is the refraction of light. Images that we see are all light rays that reach our eyes. When these light rays travel through air, they experience little or no refraction. That's why you can still see the penny through the side of the empty glass.
When you poured water into the glass, it was as though the penny had disappeared, but it was really just some bending light rays. After traveling through the water and the side of the glass, none of the rays were able to reach your eyes. Refraction occurs because of the molecules in the substance that the light rays are passing through. Gas molecules are spread out. This is why little to no refraction occurs. However, when light rays pass through a substance such as water, the refraction is greater because the molecules are closer together.
So when the light rays are traveling from the money through the water, they are refracted and cannot make it to your eyes. In fact, the glass also refracts the light even more! The image ends up being projected near the top of the glass after the light refraction it has undergone. You would be able to see it... if the saucer were not strategically placed atop the glass.
There are really two parts to this activity... the singing of the wine glass and the movement of the match. Let's discuss the singing wine glass first. As you rub your finger on the rim, your finger first sticks to the glass and then slides. This stick and slide action occurs in very short lengths and produces a vibration inside the glass which in turn produces a sound. As soon as the first few vibrations are produced, the glass resonates. That means you’re causing the crystals in the glass to vibrate together and create one clear tone. You can change the pitch (highness or lowness of the sound) by adding to or subtracting from the amount of water in the glass. The volume (loud or quiet) can be changed only a little bit by increasing or decreasing the pressure from your finger.
The movement of the match is caused by a sympathetic vibration. Because you added equal amounts of water, the second glass vibrates at exactly the same frequency as the first. The sound waves produced by the first glass travel in every direction. When those sound waves reach the second glass, the glass begins to vibrate as well and the match moves. Telekinesis? Nope... just some really clever science.
The Magic Rollback Can is a great example of transfer of energy. When you roll the can, it has kinetic energy. As it slows down, the energy is transferred into potential energy within the twisted rubber band inside the can. The twisted rubber band's potential energy is then transferred back to the can in kinetic energy as it untwists.
The secret to all this energy transfer comes from the weight that you've taped to the rubber band inside the can. While the weight is being pulled down by gravity, it is also being subjected to a twisting force from the rubber band. So long as the force being exerted by gravity on the weight is greater than the twisting rubber band's force on the weight (meaning the weight never goes over the rubber band), the rubber band will continue to twist.
Once all of the kinetic energy from the rolling can has been exhausted by converting to heat (friction) or potential energy (twisted rubber band), the can stops rolling and the weighted rubber band is able to unwind. Because of the weight in the middle of the rubber band, only the ends of the loop are able to unwind and, therefore, the can begins to roll backwards.
Polymers are long chains of molecules. Their natural state is similar to a knotted up string. When a bag of chips is made, these polymers are heated and stretched out to make the flat material used for chip bags. The high heat of this process locks the molecules in this "stretched out" state. When exposed to the heat of being microwaved, the material is able to release from the stretched state and return to its natural, bunched-up state.
But why do the shrinking polymers maintain the shape of the chip bag? This has to do with the other materials that are coating the polymer. Thin layers of aluminum, paint, and other materials line the outsides of the polymer and all of these layers are still bound together in the shape of the bag. So although the polymer chains bunch back into their natural shape, the overall bag shape is maintained.
Water is a very fickle material. The introduction of a contaminant will instantaneously drop the freezing point below 32°. Crazy, right? It's true. You witnessed it with the experiment you just did. When you added the salt, you introduced a contaminant to the frozen water of the ice. The ice then melted and refroze around the string as the "contaminated" H2O molecules were cooled by the surrounding molecules.