Under Pressure
+
ward
'
s
science
Recommended Grade Level(s):
Appropriate for: All grade levels
Time Requirements:
Activity Time: 15 minutes
Teaching Topics & Concepts:
• To illustrate expansion of gases under reduced pressure.
• Boyle's Law, pressure, force, compression, tension, stress, and strain.
• Structure and properties of matter, evidence, models, explanation, constancy, change, and measurement.
Materials:
• Shaving cream
• Marshmallow (for best results, use a fresh marshmallow)
• Soda water
• Doll's head
• Balloon
• Tape
• Vacuum pump with bell jar
Background:
Have you ever opened a can of soda, unaware that it dropped on the ground a few moments before, or had one shaken by a
prankster friend? We all know what happens next–the soda explodes in our faces. Have you been near someone opening a cham-
pagne bottle on New Year's Eve and heard the celebratory "pop"? These fizzy examples demonstrate basic concepts of gas and
pressure.
In this activity, students can observe what happens when they drastically reduce the air pressure surrounding a doll's head
filled with shaving cream. If holes are placed strategically in the doll's eyes and ears, students get a ghoulish demonstration of the
expansion of gases.
Safety
• Wear safety glasses and gloves.
• Ensure there are no cracks in the bell jar.
• Do not eat the marshmallows! Any food-grade items that have been brought are for lab use only. Do not
taste or ingest any materials in the laboratory, and do not remove any remaining food items after they have
been used in the lab.
!
