Collapsing Can

Introduction

Here’s a pressure-packed demonstration that will convince students that air exerts significant pressure!

Concepts

  • Pressure differential
  • Atmospheric pressure

Materials

Tap water, 50 mL
Hot plate
Metal can with screw top lid*
Water bath
Zetex™ gloves, for high and low temperatures
*Materials included in kit.

Safety Precautions

Be careful of the hot can and the steam created by heating the water in the can. Wear goggles and protective gloves during the demonstration.

Procedure

  1. Locate a metal can with an airtight screw top lid.
  2. Remove the lid from the metal can. Be sure the can is clean and free of chemicals—a new, unused can is preferred.
  3. Add approximately 50 mL of tap water to the metal can. This should be enough to cover the bottom of the can to a depth of approximately 1 cm.
  4. Place the can on a hot plate and heat it until the water boils and steam flows out of the uncapped hole.
  5. Using protective gloves, remove the steaming can from the hot plate. Place the can where it can be easily viewed.
  6. Immediately place the cap on the can and close tightly.
  7. The can will be dramatically crushed and it will likely do so in a loud fashion. For a quick crush, place the sealed can into an ice water bath to cool the can rapidly.

Teacher Tips

  • It is important that the cover on the can has an airtight seal. Be sure to get the lid placed tightly on the can before the cooling process begins.
  • The collapsed can and an identical un-crushed can make a nice exhibit in a classroom display case.
  • If a cap to the can is not available, try a rubber stopper. Be sure the rubber stopper fits snugly in the can opening.
  • For a more impressive implosion, immerse the can into a sink of cold water.

Correlation to Next Generation Science Standards (NGSS)†

Science & Engineering Practices

Developing and using models
Planning and carrying out investigations
Using mathematics and computational thinking

Disciplinary Core Ideas

MS-PS1.A: Structure and Properties of Matter
MS-PS3.A: Definitions of Energy
MS-PS2.A: Forces and Motion
HS-PS3.A: Definitions of Energy
HS-PS3.B: Conservation of Energy and Energy Transfer

Crosscutting Concepts

Cause and effect
Structure and function
Energy and matter

Performance Expectations

MS-PS1-4: Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
HS-PS3-2: Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motion of particles (objects) and energy associated with the relative position of particles (objects).
HS-PS3-4: Plan and conduct an investigation to provide evidence that the transfer of thermal energy when two components of different temperature are combined within a closed system results in a more uniform energy distribution among the components in the system (second law of thermodynamics).

Discussion

The tremendous pressure required to “crush” the can comes from the differential in pressure that exists between the outside of the can (normal air pressure) and the partial vacuum created inside the can by the condensing steam. The pressure differential is caused by the condensation of the steam inside the closed system as the can cools. The pressure on the outside of the can remains at atmospheric pressure (14.7 lb/in2) while the pressure inside the can is significantly reduced as the steam condenses. Remember that the can is not “sucked in”—it is the greater pressure on the outside of the can that pushes in on the can and “crushes” it. The total pressure exerted on the outside of the can may be calculated by determining the surface area of the outside of the can and multiplying this area by atmospheric pressure per unit area.

Recommended Products

Item No. Description
AP4695 Collapsing Can—Demonstration Kit

†Next Generation Science Standards and NGSS are registered trademarks of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.