Evaporativ køling af propanon/ethanol-blandinger

To investigate if there is a linear relationship between the mole composition of an Propanone/ethanol mixture and the degree of cooling through evaporation.

Identification of Variables:

Dependent variable:

• The minimum temperature reached on the probe during the evaporation.

Independent variable:

• The mole composition of the Propanone/ethanol mixture tested.

Controlled Variables:

• The amount of solvent mixture used in cooling experiment.

• The initial solvent temperature.

• The initial surface area of solvent drop being cooled.

• The surrounding air temperature.

• The amount of draught in the surrounding air.

Materials required:

Pure Propanone

Pure ethanol

Vernier data-logging interface and two temperature probes

Lap-top computer

Dropping pipettes

Boiling tubes and rubber bungs

Top-pan balance

Thick laboratory tissue paper

Clamp stands and clamps.

Procedure:

1. Place a boiling tube (balanced in a small beaker) on the top pan balance and set tare to zero.

2. Use a dropping pipette to measure about 5.00 g of Propanone into the boiling tube and quickly insert bung. Label as sample A.

3. In boiling tube B measure out about 3.50g of Propanone then re-set the tare to zero and then add about 1.50g ethanol.

4. Repeat this procedure to make a total of six samples of different compositions (A to F) finishing with pure ethanol.