Crush The Can: Difference between revisions

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== Age ==
{| class="wikitable" style="color:black; background-color:#ddd; margin-left: auto; float:right"
| [[Physics]]:
| Pressure, Vacuums
|-
| Grade Range:
| [[Elementary School]], [[Middle School]], [[High School]]
|-
| Format:
| [[Stage]]
|}


Elementary School, Middle School, High School
This demonstration is an exciting way to see how the air around us pushes on everything! We take a soda can and, by simply boiling water inside of it, we are able to get the air around us to crush the can! This demonstration works well for all ages, and can be adjusted to the age group easily.
 
== Format ==
 
Stage Show


== Materials ==
== Materials ==


    An empty aluminum can
* An empty aluminum soda can
    a small aquarium filled with water
* Bowl with water
    heat resistant gloves
* Heat resistant gloves
    propane torch
* Propane torch
    a ring to hold the can
* Can holder (ring shaped holder)
    small blast shield  
* Small blast shield


== Safety Precautions ==
== Safety Precautions ==


Science Theatre demonstrators must keep the safety of themselves and their audience in mind at all times. All Science Theatre demonstrators must have read through the Safety Training page. The ST Safety Box with first aid kit, fire extinguisher, etc. should always be available to demonstrators. Always wear safety gloves, glasses, and a labcoat if handling chemicals; always perform potentially dangerous demonstrations at a safe distance from the audience; and always keep a very close eye on any volunteers you call from the audience. This demonstration uses a propane torch, thus there is a hot flame. You must have the fire extinguisher at hand. Make sure the audience is far enough away. When you turn the can upside down to put it in the water, make sure not to splash anyone (this should be easy to avoid but its important to be aware of the possibility and be careful). Moreover you must be wearing the heat resistant gloves, a lab coat, and goggles. Hold the end of the ring with which you are holding the can to keep the distance between the flame and you a maximum. You should put up the small blast shield in front of the aquarium.
Please read the Fire Demonstration Safety and Loud Demonstration Safety sections of the [[Demonstration Safety]] page before performing this demonstration.


== Preparation ==
This demonstration requires: safety glasses, heat gloves, fire extinguisher, blast shield


Before the show, fill the aquarium 2/3 or so with water. It’s an awkward size and shape, so you’ll need a larger sink if you can find one. If one is not at hand, it may be necessary to use a smaller container to collect water which can be poured into aquarium. It would be helpful to assemble the torch by connecting the fuel container to the torch by simply twisting it tightly, but do not turn it on yet. Put the shield in front of the aquarium.


== Demonstration ==
== Demonstration ==


Fill the can with 3 centimeters of water. It is best to listen to the water as you shake the can gently. You should hear and feel some water moving in the can, but not an amount that makes it substantially heavier.
Preparation: Fill the bowl with water, and set the small blast shield in front of the bowl. Put a small amount of water in the can, measuring less than an inch deep inside the can (approximately 10mL). Set the can in the ring holder. Put on the safety glasses and heat gloves.
 
Put the can through the ring. Put on the heat resistant gloves, attach the torch to the fuel container if not yet done and turn the switch on the side of the torch to its “on” position. Holding the can with the ring and the torch with the other, position the torch so that it is aimed toward the bottom of the can, but not your fingers, your body, or the audience. Holding down the trigger of the torch begin to heat the bottom of the can. Try to evenly distribute the heat, not focusing on one spot, so that you do not burn a hole through the can.
 
Soon the water will begin to boil (maybe a minute or so). You will feel the water boiling, possibly hear it, and begin to see substantial amounts of water vapor leaving the can. Once it begins to boil, wait awhile, maybe 15-30 seconds, continuing to heat evenly. Now putting down the torch, move the can toward the aquarium. In a smooth motion, making sure not to spill any remaining water on the audience, turn the can upside down into the water. The can must be upside prior to entering the water but don’t do it too soon. The can will implode if you did it right. Let the can sit in the water. Turn of the torch, detach it from the container and take off the gloves.


== What to Say ==
# Hold the can holder in one hand, and the blowtorch in the other. Turn on the blowtorch, and heat the bottom of the can, moving the  blowtorch flame in a small circle.
# Once the water starts to boil, have the assembly give a countdown. At the end of the countdown, flip the soda can, open end first, into the bowl of water. It should crush!
# Turn off the blowtorch, and lift the soda can out of the bowl, allowing the water to drain. Wear the gloves while removing the can from the holder, as it may still be hot.


Ask the audience what they think will happen if you heat a can of water. If the answer is not given, explain that eventually the water will boil and water vapor will fill the can, escaping through the opening. Then ask them what they think will happen if they put a can full of water vapor into a cold container of water. Now begin the demo. As you set up the safety equipment, comment on why you are doing what you are doing-gloves to protect you from the flame, the shield to protect the audience, etc. As the can heats, explain what’s going on- the water molecules are gaining energy. When it begins to boil comment of the water vapor (it’s not steam) that is escaping. When you are about to turn the can over, comment on the fact that much of the water is now water vapor and has either escaped or has filled the can and is moving around energetically.
== Why This Works ==


After the can implodes, ask what happened. Tell them that when the can was placed in the water, the water vapor condensed into water. Say that this caused a change in pressure that happened so quickly the can imploded. Prior to entering the water, the can was being pushed from the outside by the air and the inside by the water vapor. Once in the water, when the vapor was quickly condensed, only the pressure of the water remained on the can, pushing inward. Because this change happened so suddenly, the can imploded.
Pressure is when a force is applied over an area. Air pressure refers to the force that the air around us is constantly applying on us. We don't notice how strong air pressure really is, since our bodies push back and we stay un-smashed. But, we can see the effects by using this can.


== Why It Is ==
When we heated the water in the can, we made it boil, and start to evaporate. Liquids take the shape of the container they are in, while gases take up all of the space within a container that they can. The steam caused the rest of the air to leave the can, leaving steam and boiling water in the can. The walls of the can could push back while it had gas (steam) inside to push against the gas (air) outside. When the can was flipped into the water, the steam inside of it condensed back to a liquid. This left a lot of empty space in the can, which we call a ''vacuum''.  Since we had no gas left inside the can, the gas outside could then exert a lot of pressure on the can and crush it!


When the can is heated it becomes filled with water vapor. This vapor occupies approximately 1000 times more space than it did as a liquid. When you turn the can over into the cool water the water vapor turns back to liquid water very quickly creating a partial vacuum in the can.
== Additional Information ==


== Real Life Examples ==
* This demonstration benefits from being performed twice in a row. The first time is to show the students and get them thinking, the second time is to explain the different parts of the experiment.
* This demonstration is a part of the [[Pressure Show]].

Latest revision as of 16:03, 8 April 2016

Physics: Pressure, Vacuums
Grade Range: Elementary School, Middle School, High School
Format: Stage

This demonstration is an exciting way to see how the air around us pushes on everything! We take a soda can and, by simply boiling water inside of it, we are able to get the air around us to crush the can! This demonstration works well for all ages, and can be adjusted to the age group easily.

Materials

  • An empty aluminum soda can
  • Bowl with water
  • Heat resistant gloves
  • Propane torch
  • Can holder (ring shaped holder)
  • Small blast shield

Safety Precautions

Please read the Fire Demonstration Safety and Loud Demonstration Safety sections of the Demonstration Safety page before performing this demonstration.

This demonstration requires: safety glasses, heat gloves, fire extinguisher, blast shield


Demonstration

Preparation: Fill the bowl with water, and set the small blast shield in front of the bowl. Put a small amount of water in the can, measuring less than an inch deep inside the can (approximately 10mL). Set the can in the ring holder. Put on the safety glasses and heat gloves.

  1. Hold the can holder in one hand, and the blowtorch in the other. Turn on the blowtorch, and heat the bottom of the can, moving the blowtorch flame in a small circle.
  2. Once the water starts to boil, have the assembly give a countdown. At the end of the countdown, flip the soda can, open end first, into the bowl of water. It should crush!
  3. Turn off the blowtorch, and lift the soda can out of the bowl, allowing the water to drain. Wear the gloves while removing the can from the holder, as it may still be hot.

Why This Works

Pressure is when a force is applied over an area. Air pressure refers to the force that the air around us is constantly applying on us. We don't notice how strong air pressure really is, since our bodies push back and we stay un-smashed. But, we can see the effects by using this can.

When we heated the water in the can, we made it boil, and start to evaporate. Liquids take the shape of the container they are in, while gases take up all of the space within a container that they can. The steam caused the rest of the air to leave the can, leaving steam and boiling water in the can. The walls of the can could push back while it had gas (steam) inside to push against the gas (air) outside. When the can was flipped into the water, the steam inside of it condensed back to a liquid. This left a lot of empty space in the can, which we call a vacuum. Since we had no gas left inside the can, the gas outside could then exert a lot of pressure on the can and crush it!

Additional Information

  • This demonstration benefits from being performed twice in a row. The first time is to show the students and get them thinking, the second time is to explain the different parts of the experiment.
  • This demonstration is a part of the Pressure Show.
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