3B Scientific Air Cushion Plate - Manual (Page 31)

Physical Experiments on the Air-Cushion Table
32
The larger the mean velocity of the hover discs
is, the faster individual discs will leave the origi-
nal section.
Interpretation:
A liquid contains molecules of different veloci-
ties at all times. The fastest among these molecu-
les succeed in leaving the liquid. This process of
evaporation also occurs beneath the boiling tem-
perature of the liquid. Since molecules from the
gas atmosphere also return into the liquid, a dy-
namic equilibrium state is soon reached.
The speed of evaporation increases as the tem-
perature rises.
Note:
The inclination of the experiment surface simulates
the gravitational field. This makes more particles
return from the gas phase into the liquid phase.
2.2.6 Liquefaction of a Gas through Pressure
Components:
Air-cushion table with fan
Overhead projector
Magnetic barrier, long
2 Pieces
Magnetic barrier, short 2 Pieces
Magnetic piston 1 Piece
Guide piece for the
magnetic piston
l Piece
Hover disc, red 20 Pieces
Model simulation
Real Object Model
Vessel containing Experiment surface of
the liquid the air-cushion table
Walls of the vessel Magnetic barriers
Piston for the com- Magnetic piston
pression of the gas
Gas molecules
Hover discs
How to proceed:
Align the air-cushion table horizontally and attach
the magnetic barriers. Place the piston on the
experiment surface right next to barrier no. 2. The
guide piece for the magnetic piston placed onto
magnetic barrier no. 2 ensures excellent guidance
of the piston rod. Arrange the magnetic hover
discs near barrier no.1.
Turn the fan to a medium setting. Slowly move
the piston towards barrier no.1 until the available
area for the hover discs is less than half of the
experiment surface. Observe the configuration
and motions of the hover discs.
Result:
Reducing the area in size changes the behavior
of the hover discs. The number of impacts in-
creases. The distances in which the hover discs
can move in a straight line become shorter and
shorter. Oscillating and circular motions prevail.
Permanent changes in location mostly occur as a
mutual exchange of positions.
Interpretation:
Under certain conditions, the compression of a
gas can result in liquefaction. The configuration
of the molecules and their type of motion change
in this process. While in the gaseous aggregati-
on state only translational movements occur, the
motion prevailing in the liquid state is oscillati-
on around the respective location.
2.2.7 Solidification of a Liquid
Components:
Air-cushion table with fan
Overhead projector
Magnetic barrier, long
2 Pieces
Magnetic barrier, short 2 Pieces
Air-cushion table with fan
Overhead projector
Magnetic barrier, long
2 Pieces
Magnetic barrier, short 2 Pieces
Hover disc, orange 25 Pieces
Model simulation
Real Object Model
Vessel containing Experiment surface of
the liquid the air-cushion table
Walls of the vessel Magnetic barriers
Molecules of the Hover discs
liquid
How to proceed:
Align the air-cushion table horizontally and attach