The Density And Volume Of A Water-Alcohol Mixture - Wikieducator Page 2

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2. Perform six sets of measurements as follows and record the results in Table 1. If a volume required
is “0.0”, simply measure out the other liquid and continue. For each trial (HORIZONTAL line) in the
Table perform parts 2(a) to 2(c) of this experimental step.
(a) Flick the “water” cylinder several times to shake it dry and dry the outside of the cylinder. Then
ACCURATELY measure the volume of water required (use a dropping pipette to be sure that the
bottom of the water’s meniscus line just touches the required volume marking). After adding the
water, weigh the cylinder and water and enter the data in column 1 of Table 1. Keep the water in
the cylinder for use in part 2(c).
(b) Flick the "alcohol" cylinder several times to dry it. Dry the outside of the cylinder. Then
ACCURATELY measure the required volume of alcohol . Again, use a dropping pipet to be sure
the alcohol’s meniscus line touches the volume marking. After adding the alcohol, weigh the
cylinder and alcohol and enter the data in column 2 of Table I. Keep the alcohol for part 2(c).
(c) Carefully, WITHOUT LOSING ANY LIQUID, mix the water and alcohol back and forth, FINALLY
HAVING THE MIXTURE END UP IN THE ALCOHOL CYLINDER. Let the last of the mixture
drain from the water cylinder into the alcohol cylinder for about 15 seconds. (In order to correctly
analyze the data, the mixture MUST end up in one cylinder all the time and we are arbitrarily
choosing to use the ALCOHOL CYLINDER for measurements on the mixture.) Then measure
• the volume of the mixture to the nearest 0.1 mL. Enter the volume in column 3 of Table I.
• the mass of the alcohol cylinder and mixture to 0.01 g. Enter the mass in column 4 of Table
1.
Finally, discard the mixture down the sink.
ANALYSIS OF DATA
1. Fill in Table 2 as follows.
Column 1 (mass of water)
Calculate the mass of water used in each trial by subtracting the Mass of empty “water”
graduated cylinder (recorded at the start of the DATA section) from each entry in column 1 of
Table 1. DO NOT CHANGE THE VALUES IN TABLE 1. Enter the results in the corresponding
space in column 1 of Table 2.
Column 2 (mass of alcohol)
For each trial, subtract the Mass of empty “alcohol” graduated cylinder from each entry in
column 2 of Table 1. Enter the results in column 2 of Table 2.
Column 3 (volume of mixture)
Copy, unchanged, each entry from column 3 of Table 1 to column 3 of Table 2.
Column 4 (mass of mixture)
For each trial, subtract the Mass of empty “alcohol” graduated cylinder from each entry in
column 4 of Table 1. Enter the results in column 4 of Table 2.
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Column 5 (the sum of the masses of water and alcohol in each mixture)
For each trial, add the mass of water in column 1 of Table 2 to the mass of alcohol in column 2 of
Table 2 for each trial. Enter the results in column 5 of Table 2.
Column 6 (the mass lost during the mixing process)
For each trial, subtract the mass of the mixture (column 4 in Table 2) from the combined mass
given in column 5 of Table 2. Enter the results in column 6 of Table 2. [The entries in column 5
should be very close to the values in column 4. Column 6 tells us how much mass is lost by
being left behind in the water cylinder (or by spillage) when the alcohol and water are mixed and
poured back into the alcohol cylinder. Columns 5 and 6 are not used for calculations. Instead,
columns 5 and 6 serve as a check on how carefully you carried out the experiment.]