PHSC 101 BSU Density & Specific Gravity Experimental Materials Lab Report

Earth Science (PHSC 101) Virtual Lab Expt. #3: Density and SpecificGravity
Name: ________________________ Section: _______ Date: ______
Note on this virtual Lab Experiment
Read the introductory principle, procedure and experimental materials outlined below,
and understand as to how this virtual experiment would be conducted under real lab
condition to generate the theoretical data supplied in Tables below. After clearly
understanding the procedure and the formula for the calculations, enter calculated values
in the blank columns and write brief discussions as per the guideline, and resubmit the
completed assignment in the Drop Box.
Introduction
Density
Density is a physical property of solids and fluids that can be defined as the mass (m)
or quantity of a substance contained in one unit of its volume (v).
m
d=
v
The density of water is 1.0 g/ml (1g/cm3); in other words, 10ml has a mass of 10g.
Specific Gravity
Specific gravity of a body is that number which denotes the ratio of the mass of a body
and the mass of equal volume water.
Specific gravity = Mass of solid or liquid
Mass of an equal volume of water
Water is used as the standard, because the density of water does not vary by more than
1
/2 of a percent over the temperature range of zero to 30-degree Celsius.
The density and specific gravity of any substance are numerically the same when the
density is expressed in g/ml. When density is expressed in g/ml (g/cm3), specific gravity
can be calculated by dividing the density value by 1 g/ml (1g/cm3), thus making it unitless. Example, for copper: density is 8.5 g/ml (g/cm3); specific gravity is 8.5.
Standard specific gravities (densities) values of some materials are shown below:
Water
1.0 (1g/cm3)
Aluminum 2.7 (2.7g/cm3)
Copper
8.5 (8.5g/cm3)
Steel
7.8 (7.8g/cm3)
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The main objective of this experiment is to determine the densities and specific gravities
of different materials and compare them with their standard values.
Materials and Procedure
Equipment
• Beakers
• Analytical Balance
•
Metal rounds
Graduated cylinders
Metal pieces (small)
Overflow-cup with nozzle
Experimental Procedure
1. Density of water
• A 100ml graduate cylinder is filled with water more than half and read the
exact volume in ml is read to one decimal place, and record in Table 1, under
the column designated volume of water (ml), Rep #1, third column.
• A 150ml beaker is tared (zero) on analytical balance.
• The volume of water in the cylinder is transferred quantitatively into the
beaker; mass in grams of water in the beaker is measured, and data record
under mass of water (g), in the second column, Rep #1
• The same procedure is repeated for Rep #2 and #3, the mass and volume data
recorded in the appropriate columns.
Assignment
The theoretical data generated for mass and volume of water are already given in
Table 1 below. From these data, calculate the density and % error values, using
the formulae given and enter values in the respective blank spaces (last column):
• The density of water (d) is calculated by dividing the mass (m) in grams of
water to the volume (v) of water in ml.
• The mean density values are calculated by adding the three replications and
dividing by 3.
• The error % as compared to the standard density of water, which is 1g/ml,
is calculated using the following formula.
% Error = */Standard value – observed mean/ x 100
Standard value
*absolute difference (no negative sign)
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Table 1. Density of water
Replicate
#1
#2
#3
Mass of water
(g)
80
90
100
Volume of water
(ml)
84
92
103
Mean (average)
% Error
Density
(mass/volume)
(g/ml)
2. Density of pieces of metal (copper)
• Some metal pieces (copper) provided are weighed on a balance (about 60g)
and the exact weight in gram recorded in Table 2, under mass (g) in column
2, Rep #1.
• A 100-ml cylinder is filled to about 50 ml of water and exact volume in ml is
recorded under the V1 column, Rep #1.
• The weighed metal pieces are immersed into the water in the cylinder.
• The new volume of water in ml is recorded under the V2 column in the data
Table 2, which is the volume after immersing the metal pieces.
• The change in volume of water (V2 – V1) is calculated and recorded (This is
the actual volume in ml of the metal pieces).
• This procedure is repeated in the same manner to complete Rep #2 and #3.
Assignment
The theoretical data generated following the procedure outlined above are given
in Table 2 below. From these data, calculate the density and % error values and
enter in the last column blank spaces.
• Density of metal pieces is calculated by dividing mass of metal by change in
volume, (g/ml)
• The mean density values are calculated by adding the three replications and
dividing by 3.
• The error % as compared to the standard density of copper, which is
8.5g/ml, is calculated using the formula given under density of water
measurement.
Table 2. Density of pieces of metal
Replicate
#1
#2
#3
Mass
(g)
60
70
80
Initial volume
of water
(V1)
50
50
50
Volume (ml)
Final volume
of water
(V2)
57
58
59
Density
Actual volume
of metal pieces Mass/volume
(g/ml)
(V2 – V1)
7
8
9
Mean (average)
% Error
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3. Density of metal rounds (steel)
• The mass in gram of three metal round (steel) provided is measured one at a time
and data entered in Table 3, under column 2, Replications #1, #2, #3,
respectively.
• Overflow-cup with a drain-nozzle is placed on a bench above the water sink and
filled with water until excess water flows out through the nozzle and levels off.
• After the excess water stops dripping out of the overflow-cup, an empty beaker is
held under the nozzle with one hand and the metal round, of which mass entered
in Rep #1, is gently dropped in the water with the other hand; the metal will
displace a fraction of the water and water flows out through the nozzle into the
beaker.
• The content of the beaker is then poured into a small, graduated cylinder, and the
volume is measured in ml and data recorded under volume of metal column.
• The experiment described for Rep #1 is repeated in the same manner for metal
rounds 2, and 3, and data entered in Row 2 and 3, in the appropriate columns.
Assignment
The theoretical data generated following the above outlined procedure are given
Table 3 below. From the given data, calculate and enter the density for each
replication, the mean density value, and the % error of the experiment, using the
given formulae.
• The density (g/ml) of the metal is calculated for each replication by dividing the
mass of metal round (g) by the volume of metal (ml), and results entered in the
last column.
• The mean density values are calculated by adding the three replications and
dividing by 3.
• The error % as compared to the standard density of steel, which is 7.8g/ml, is
calculated using the formula given under density of water measurement.
Table 3. Density of round metal (steel)
Replicate
#1
#2
#3
Mass of metal
(g)
70
95
120
Volume of metal
(ml)
9.5
13.5
16.0
Mean (average)
% Error
Density
mass/volume
(g/ml)
Discussion
In the space provided below, briefly discuss the results of each of your experiments by
indicating the mean and percent error values. Also indicate the level of precision of
the experiment, by comparing the measurement results in the different replications, as
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well as the level of accuracy of the experiment by comparing the means with their
respective standard values. Try to give explanation for the level of error obtained by
indicating possible sources of error, if high % error (>10%) is observed.
1. Density of water
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2. Density of metal pieces
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3. Density of metal rounds
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