3B Scientific Vacuum Student Kit - Manual (Page 4)

4
4. Sample experiments
4.1 Lowering of the boiling point of liquids
•
Set up the apparatus as in the illustration.
• Fill the beaker with warm water and measure its
temperature.
•
Put the beaker on the experiment plate and place
the bell jar over the top of them.
• Press the jar onto the plate and operate the pump
until the liquid visibly starts to boil.
•
Loosen the hose connection to the jar to let in air.
•
Measure the temperature of the liquid once again.
• Compare the two temperatures and discuss.
4.2 Effect of reduced air pressure on a balloon
•
Set up the apparatus as in the illustration.
• Put a partially inflated balloon on the experiment
plate and place the bell jar over the top of them.
•
Press the jar onto the plate and operate the hand
pump 10-15 times.
• The balloon inflates.
• Alternative experiments can be performed using a
mini bellows or a small quantity of shaving foam in
a beaker.
4.3 Determining the mass and density of air
Also required:
1 set of scales measuring to the nearest 0.01 g
1 measuring beaker
• Press the bell jar and experiment plate together. At-
tach hose 2 and determine the total weight.
• Connect the hand pump and evacuate the recipient.
• Loosen the connection between hoses
1 and 2
and measure the total weight of evacuated jar and
hose connection.
• The difference in weight indicates the mass of air
pumped out.
• Let air into the bell jar.
• Re-attach hose
2 to determine the volume.
• Fill the recipient and hose
2 with water adding a
bung or holding your finger over the end of the hose.
• Pour the water into a measuring beaker and read off
the volume.
• Determine the density of air by dividing the mass by
the volume.
4.4 Filling a pipette without touching it
•
Set up the apparatus as in the illustration.
• Fill a beaker with water and place it on the experi-
ment plate.
•
Put the open end of the pipette in the beaker and
place the bell jar over the lot.
• Press the jar onto the plate and operate the hand
pump a few times.
•
Air disappears from the pipette.
•
Let air into the recipient and the pipette will fill with
water.
3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany • www.3bscientific.com • Technical amendments are possible