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Whelmer #3: Dancing Penny
Description:
A coin is mysteriously made to dance on the top of a glass soda bottle.
Science process skills:
- observation
- inference
- identifying variables
Complex reasoning strategies:
- comparison
- deduction
Standards:
K-4:
- Employ simple equipment and tools to gather data and extend the senses
(Standard A.1.3).
- Heat can move from one object to another by conduction (Standard B.3.2).
5-8:
- Energy is a property of many substances and is associated with heat...
Energy is transferred in many ways (Standard B.3.1).
- Heat moves in predictable ways, flowing from warmer objects to cooler
ones, until both reach the same temperature (Standard B.3.2).
9-12:
- Everything tends to become less organized and less orderly over time.
Thus, in all energy transfers, the overall effect is that the energy
is spread out uniformly. Examples are the transfer of energy from hotter
to cooler objects by conduction, radiation, or convection (Standard
B.5.4).
Above Standards from the National
Science Education Standards.
Content topics:
- conduction of heat
- relationship between temperature and pressure (gases)
- body heat/energy
You will need:
- empty soft drink bottle (glass bottles are best, but plastic bottles
will work)
- pennies, dimes, nickels
- a few drops of water or cooking oil
Instructions:
Chilling the bottle for several minutes before presenting the demonstration
will increase the effect but is not necessary. Select a coin which will
"seat" in the opening of the bottle without falling into the bottle. You
may need to try different coins and bottles to find an acceptable combination.
Presentation:
Lay the coin flat over the opening of the bottle.
Place a few drops of water or cooking oil at the edge of the coin, to form
a seal between the coin and the lip of the bottle.
Wrap both hands around the body of the bottle. Direct students to quiet
themselves and focus their attention on the coin. The coin will begin to
tap on the lip of the bottle. If the coin does not tap, warmed air might
be escaping between the coin and the lip of the bottle. Add a few more drops
of water or oil.
Elicit explanations from students. Allow them to try different methods to
increase the effect. (rubbing hands together to create more heat; or chilling
the bottle)
After explaining that heat was conducted from the hands to the air, causing
it to expand, challenge students to trace the origins of the energy that
caused the coin to move (body heat, energy from food, the sun). Also, where
did that energy go? (It dissipated to the surroundings.)
Content:
In a closed container of any gas, there is a direct relationship between
temperature and pressure; as temperature increases, so does pressure. The
pressure increase is caused by the increase in motion of the gas molecules
as they become warmer. The added energy (provided by the warm hands) increases
the motion of the gas molecules until they lift the coin. As some of the
gas escapes, the coin drops.
Scientists have heated gas molecules to millions of degrees, with a great
increase in their energy of motion. Also, scientists have cooled gas molecules
to near absolute zero, the temperature at which molecules slow down until
they have no motion. Absolute zero is -273°C. There is no "colder"
temperature. Molecules can move no slower than standing still!
Assessment:
Type: individual assessment.
Content/Process: relationship between temperature and pressure.
Age/Level: intermediate grades and higher.
Manufacturers of products in aerosol cans warn us to keep these cans away
from heat. Based on the activity you have just completed, explain why this
caution is given to the consumer. Use diagrams to show the forces that support
your conclusion.
Assessment should be based on the student's understanding of the expansion
of gases when heated. Young students may have to be informed about the construction
of aerosol cans before they can address this problem.
Notes:
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