Mike Isley
Product Developer

One of the most popular teacher demos to illustrate the power of atmospheric pressure is to heat to a boil a small amount of water in an aluminum beverage can, then quickly submerge its mouth in an ice water bath. The walls of the can suddenly implode because the atmospheric pressure is greater than the can’s interior pressure. Students can do this activity as a quantitative guided-inquiry exercise to show the relationship between temperature, pressure, and volume of gases.¹

Background

Atmospheric pressure at sea level is 101.3 kilopascals, 760 mm mercury, or 14.7 lb per square inch. This would be the amount of pressure exerted on the outside of any empty beverage can. Since the can is open, the air pressure on the inside of this can is the same as the outside pressure. Therefore, the equilibrium of pressures enables the can to maintain its shape. When a small amount of water (20 mL) is added to the can and brought to a boil with a hot plate or Bunsen burner, the water changes into water vapor, driving out all of the air in the can and occupying all of the inside volume. When the can is quickly inverted and placed mouth down in an ice water bath, the water vapor molecules slow down and condense back into liquid water. As a result, the gas volume and pressure inside drops suddenly, creating a partial vacuum. With the drop in pressure inside the can and the atmospheric pressure remaining constant outside it, the imbalance of pressures causes the walls of the can to dramatically collapse.

The activities that follow can be done as demonstrations or in lab groups of 2 to 4 students.

Materials

For teacher demonstration or each lab group of 2 to 4 students

• Plastic Tub
• Laboratory Thermometer, –20 to 110° C
• Beaker Tongs
• Safety Goggles
• 7 Empty Aluminum Beverage Cans, 12 fl oz
• Graduated Cylinder, 100 mL
• Beaker, 400 or 600 mL
• Hot Plate (or Bunsen burner with iron ring, wire gauze, and ring stand)
• Ice
• Graph Paper (or spreadsheet program with graphing)
• Video Camera (or cell phone camera)
• Source of Tap Water

Activity 1: Classic implosion

Procedure

1. Place 20 mL of water in an empty aluminum beverage can.
2. Place the can on a hot plate or wire gauze on a ring stand with a Bunsen burner.
3. Make an ice water bath with water and ice. This bath should be 0 to 5° C.
4. Heat the can until the water inside starts to boil (100° C) and steam is emitted.
5. Designate a student to film the next step with a video or cell phone camera.
6. With beaker tongs, quickly invert and submerge the can, mouth down, in the ice water bath.
7. The can will immediately implode, like the one in the following video.²

Suggested inquiry activities

Use 3 additional empty aluminum cans for each of the activities that follow.

Activity 2: Varying the temperature of water in the can

Procedure

1. Heat the 20 mL of water in each can at 10° intervals of 80° C, 90° C, and 100° C.
2. Invert and submerge each in an ice water bath at 0° C.
3. Observe the amount of implosion for each. Have students determine if there is a difference.
4. Empty the water from each can, then determine each of their volumes by filling them with water from a graduated cylinder.
5. Plot the volume of the imploded cans on the y axis verses the temperature of the water in the cans on the x axis. Have students determine if there is a relationship between these variables, and if so, why.

Activity 3: Varying the temperature of the water bath

Procedure

1. Heat 20 mL of water to boiling inside each can, but change the temperature of the water bath by 25° increments for each; for example, 0° C, 25° C, and 50° C.
2. Invert and submerge each of the cans in the water bath at the given temperatures above.
3. Repeat step 4 from Activity 2 above to determine the volume of each imploded can.
4. Plot the volume of the imploded cans on the y axis versus the temperature of the water bath on the x axis. Have students determine if there is a relationship between these variables, and if so, why.

Answers to questions

Activity 2

3. Observe the amount of implosion for each. Have students determine if there is a difference.
   Yes, there is a difference. The higher the temperature of the water inside the can, the more severe the implosion.

5. Plot the volume of the imploded cans on the y axis versus the temperature of the water in the cans on the x axis. Have students determine if there is a relationship between these variables, and if so, why.
   Yes, there is an inverse relationship. As the temperature of the water inside of the can gets higher, the volume left in the can after the implosion is less. This is because more water vapor condenses when it is submerged, creating a greater implosion.

Activity 3

4. Plot the volume of the imploded cans on the y axis versus the temperature of the water bath on the x axis. Have students determine if there is a relationship between these variables, and if so, why.
   Yes, there is a direct relationship. As the temperature of the water bath increases, fewer water molecules condense as the can is submerged, causing a smaller vacuum that leaves a larger volume after the implosion.

Sample data

Activity 2: Varying the temperature of water in the can

Figure 1   Imploded cans with interior water from left to right at 100° C, 90° C, and 80° C.

Water Temp. in Can (°C)	Imploded Volume (mL)
100	145
90	246
80	357

Activity 3: Varying the temperature of the water bath

Water Bath Temp. (°C)	Imploded Volume (mL)
0	209
25	239
50	258

Footnotes

¹Eichler, J. 2009. Imploding Soda Cans: From Demonstration to Guided-Inquiry Laboratory Activity. Journal of Chemical Education 86 (4): 472–474.

²Coke Can Implosion. Available at: http://wn.com/coke_can_implosion  Accessed January 8, 2014.