Chemistry Reference
In-Depth Information
Material: Gas liquefaction pump, camping gas cartridge, hose; butane (F
+
)
from the camping gas cartridge.
Procedure: The pump is to be opened and filled totally with butane by air
displacement (get the hose deep into the cylinder and take it out slowly).
The piston is being attached, pushed firmly into the cylinder of the pump
and locked. The locking mechanism is being loosened and the liquid butane
is being observed. This process can be repeated many times.
Observation: A big drop of liquid butane forms, when the gas is being
compressed, the gas volume decreases to one-tenth. After the locking
mechanism is being loosened, the piston moves out of the cylinder to the
same extent as before, the drop disappears and cools down the bottom of the
cylinder: the gas volume is the same as at the beginning.
E1.15.
Evaporation and Condensation of Ethanol
Problem: Young students accept that matter consists of smallest particles:
ethanol particles exist in ethanol, water particles exist in water. When they
have to interpret small particles in a gas and are asked about the space
between the particles, they mostly think of “air” or “other material.” To
demonstrate that there is nothing between those particles, ethanol is
evaporated first to show the big volume compared with the liquid volume
and then it is cooled down and condensed to the same very little volume as
before: no air or other material is observed. The bigger volume of ethanol
vapor should be interpreted by the higher movement of the ethanol particles
and bigger distances between the particles.
Material: Beaker (2 L), electric heater, balloon, pipette, tweezers; ethanol.
Procedure: 1 L of water is heated in the beaker until it keeps boiling (at
100
C at normal pressure). 1-2 mL of ethanol are given into the balloon,
closed by a knot and thrown into the boiling water (ethanol boils at 79
C).
After some time the balloon is taken out of the water and thrown again into
the boiling water.
Observation: The balloon increases to a volume of about 200-300 mL, after
cooling down the same small volume of 1-2 mL as before is to be observed.
Throwing the balloon again into the boiling water, the same big volume
appears as before.
