April 2014

Alka-Seltzer Rockets (4/30/14)

MATERIALS

  • Alka-Seltzer tablets
  • Film canisters with snap-on lids
  • Water
  • Safety glasses
INSTRUCTIONS
  1. Safety first! Protect your eyes with safety glasses.
  2. Fill a film canister one-half full with water.
  3. Drop an Alka-Seltzer tablet into the film canister.
  4. Quickly snap the lid on as tight as you can! What is going on inside the film canister?
  5. Stand back, and wait for it… What happens?!

HOW DOES IT WORK?
The secret to shooting an Alka-Seltzer rocket is hidden in the tiny, fizzy bubbles that you see bouncing around in the Alka-Seltzer water.  Take a look at the list of ingredients on the Alka-Seltzer package. Do you see citric acid and sodium bicarbonate listed?  These two chemicals react together when placed in water. The chemical reaction produces carbon dioxide gas! We can’t see carbon dioxide, but the gas slowly builds up pressure inside of the container…  And the container can only handle so much pressure! The path of least resistance for the carbon dioxide to escape is usually through the lid (instead of the stronger sides or bottom of the container) which causes the lid to pop off!

NOW TRY THIS!

  • What amount of water produces the best rocket fuel? One-quarter full, completely full, or somewhere in the middle? You decide!
  • Does the temperature of the water change the distance the rocket travels? Does it change the time you have to wait for the rocket to blast off? Try using cold, lukewarm, and hot water! Measure how high the rockets travel, and time each trial!
  • Try turning the film canister upside down after dropping in the Alka-Seltzer tablet and securing the lid! What happens?

The Egg Drop (4/16/14)

MATERIALS

  • Eggs
  • Water
  • Large drinking glass
  • Toilet paper tube
  • Aluminum pie pan

INSTRUCTIONS

  1. Fill the glass with water about three-quarters full.
  2. Place the pie pan on top of the glass.
  3. Position the toilet paper tube on top of the pie pan directly over the water.
  4. Balance an egg on top of the toilet paper tube.
  5. Using your dominant hand, whack the edge of the pie pan horizontally. Make sure you follow through, without hitting the glass!
  6. You will be surprised to see the egg fall straight down into the glass without breaking!

HOW DOES IT WORK?
Newton’s First Law of Motion states that an object at rest will stay at rest, and an object in motion will stay in motion unless acted upon by an unbalanced force. Since the egg is not moving while it is resting on top of the toilet paper tube, that’s what the egg wants to continue doing. When you apply enough force to the pie pan, the pan will hook the bottom of the toilet paper tube which floats away with the pan. At this point, you have knocked out the support from underneath the egg using very little friction. The force of gravity then takes over, and pulls the egg down into the glass.

 

The Floating Egg (4/16/14)

MATERIALS

  • 2 drinking glasses
  • Eggs
  • Water
  • Salt
  • Spoon

INSTRUCTIONS

  1. Fill one of the glasses almost to the top with water.
  2. Drop an egg in the glass. What happens?
  3. Fill the second glass halfway full with water.
  4. Stir approximately 4 tablespoons of salt into the water.
  5. Fill up the rest of the glass with fresh water.
  6. Carefully drop an egg into the glass. What do you see?

HOW DOES IT WORK?
The first egg sinks in fresh water because the egg has more density than water. This means that the egg has more stuff (matter) packed into a specific area (volume) than the same amount of water. When you add salt to the water, you increase the density. If you stir in enough salt, the density of the water will then be greater than the egg, which makes the egg float. If you weigh a cup of saltwater and a cup of fresh water, the saltwater will weigh more than the fresh water even though it is taking up the same amount of space! That’s because salt water is denser than fresh water.

NOW TRY THIS!

  • Does it make a difference if you use hard-boiled eggs instead of raw eggs?
  • Try using different liquids to float and sink eggs! Will an egg float in sugar water?

 

Ivory Soap Souffle (4/2/14)

MATERIALS

  • Bar of Ivory soap
  • Various bars of another brand of soap
  • Bowl of water (or a plastic tub)
  • Paper towel or paper plate
  • Microwave oven

INSTRUCTIONS

Note: Always make sure that you have permission to use the microwave oven!

  1. Put the bar of Ivory soap in the middle of a piece of paper towel or paper plate, and place the whole thing in the center of the microwave oven.
  2. Heat the bar of soap on HIGH for 2 minutes. Don’t take your eyes off the bar of soap as it begins to expand and transform into puffy clouds. Be careful not to overheat your soap soufflé.
  3. Let the soap cool down for a few minutes before touching it. What do you see? The soap is fluffy but stiff. Don’t throw away the soap when you’re done! You can still use it even though it may have a somewhat different shape and size.

HOW DOES IT WORK?

So why does the soap grow in the microwave? This phenomenon is actually very similar to what happens when popcorn pops or when you microwave a marshmallow. Ivory soap is unique because air is pumped into it during the manufacturing process.Those air bubbles in the soap (or the popcorn kernels or the marshmallow) contain water. When the water is heated by the microwave, it creates an incredible expanding effect. The water vaporizes which forms bubbles, and the heat causes trapped air to expand. The heat also causes the soap to soften and become flexible.

This effect is actually a demonstration of Charles’ Law. Charles’ Law states that as the temperature of a gas increases, so does its volume. When the soap is microwaved, molecules of air in the soap move rapidly, causing them to move away from each other. This causes the soap to puff up into an amazing soap sculpture!

NOW TRY THIS!

  • Place Ivory soap in a bowl of water along with some other brands of bar soap. Which ones float? Why does this happen? Break the bars of soap in half. Can you see any air pockets hiding in the middle of the bar?
  • Microwave other brands of soap. Which ones expand the most?