258 DIY Science: Illustrated Guide to Home Chemistry Experiments
- With the cap removed, slide the plunger in and out of
the syringe several times to distribute the lubricant.
There should be little discernible resistance when
moving the plunger. - Adjust the plunger to about 75% of the maximum
capacity of the syringe. For example, with my 10 mL
syringe, I set the initial volume to 7.5 mL. If the plunger
seal has multiple wipes (as are visible in Figure 14-2), the
bottom wipe is the one that matters. Once the plunger is
in the correct position, reinstall the cap on the syringe. - Clamp the syringe as shown in Figure 14-4. Make sure
that the cap of the syringe is pressing directly against
the bottom of the beaker. Otherwise, when you add
mass to the container, the cap may pop off the syringe. - Obtain the atmospheric pressure using a barometer or
from a local radio or TV broadcast. Convert that value to
Pa and enter it on line C of Table 14-3. - Verify the initial volume reading on the syringe, and
record that value as accurately as possible on line D of
Table 14-3. (Your syringe may use cc graduations, which
are the same as mL graduations for our purposes.)
Fill the beaker with tap water at room temperature,
making sure that the gas-filled portion of the syringe
body is as far below the water line as possible. Record
the temperature on line E of Table 14-3.
Bring the water to a boil, and allow it to continue boiling
for at least two or three minutes to give the gas in the
syringe a chance to equilibrate. Record the temperature
on line F of Table 14-3. (Do not assume 100°C; the actual
boiling point of water varies with atmospheric pressure.)
Carefully add lead shot to the container while watching
the volume reading on the syringe. When the volume
approach the initial volume, “bump” the plunger carefully
by raising the container once or twice and then allowing
it to come to rest on the plunger again. Continue adding
lead shot until the volume is as close as possible to the
original volume.
Remove heat from the beaker and allow it to cool. While
it cools, weigh the lead shot in the container and record
its mass on line G of Table 14-3.
Using the combined masses of the empty container,
plunger, and lead shot, calculate the pressure as
described in Laboratory 14.1. Enter that value on line H
of Table 14-3.
POCEDURER
1.f you have not already done so, put on your splash I
goggles, gloves, and protective clothing.
- Use the caliper to measure the inside diameter of
the syringe bore in millimeters. Calculate the surface
area of the syringe bore by dividing the diameter by
2 to determine the radius, squaring the radius, and
multiplying by pi (π, 3.14159). Divide by 1,000,000 to
convert the result from square millimeters to square
meters and enter that value on line A of Table 14-3. (The
number you obtain will be very small. For example,
my syringe has an internal bore of 15.0 mm, which
corresponds to an area of 0.000177 m^2 .) - Weigh the container and syringe plunger (just the
plunger—not the body of the syringe) together, and
record their combined mass on line B of Table 14-3. - Spread a tiny amount (~1 drop) of mineral oil or
petroleum jelly on the seal at the bottom of the plunger.
Use just enough to lubricate the seal so that it slides
freely within the body of the syringe.
10.
11.
12.
13.
14.
FIGURE 14-4: Our apparatus for verifying Gay-Lussac’s Law
dISoALp S : No waste products are produced in this
laboratory session. Save the lead shot for future use.