Refer to Lab Manual & Worksheets

01_09
(a) (b) (c)
Rank the images from best to worst precision.
A) a > b > c B) b > c > a C) c > a > b D) c > b > a

01_09
(a) (b) (c)
Rank the images from best to worst precision.
A) a > b > c B) b > c > a C) c > a > b D) c > b > a

01_09
(a) (b)
(c)
Rank the images from best to worst accuracy.
A) a > b > c B) b > c > a C) c > a > b D) c > b > a

01_09
(a) (b) (c)
Rank the images from best to worst accuracy.
A) a > b > c B) b > c > a C) c > a > b D) c > b > a

QUESTION
Two Chem 120 students are each drinking a can of cranberry juice after class. The printed label indicates that the respective volume of both containers is 375 milliliters. Euna remarks that the Federal
Trade Commision (FTC) requires bottlers to be very precise. Mike correctly responded:
A. If precision were the only requirement, bottlers could claim any volume as long as it was always very nearly the same volume.
B. Since precision is a requirement, bottlers have to get exactly
375 mL in every can.
C. Bottlers must have a precise average of all of the containers in a case of soft drinks equal to 375 mL.
D. If there were a difference of no more than +/- 1 mL between containers, the bottlers can sell their beverage.

Answer
Two Chem 120 students are each drinking a can of cranberry juice after class. The printed label indicates that the respective volume of both containers is 375 milliliters. Euna remarks that the Federal
Trade Commision (FTC) requires bottlers to be very precise. Mike correctly responded:
A. If precision were the only requirement, bottlers could claim any volume as long as it was always very nearly the same volume.
B. Since precision is a requirement, bottlers have to get exactly
375 mL in every can.
C. Bottlers must have a precise average of all of the containers in a case of soft drinks equal to 375 mL.
D. If there were a difference of no more than +/- 1 mL between containers, the bottlers can sell their beverage.

(The Following Measured Data is for Volume in mL) a) a)
9.5 2
8.3 6
7.2 9
8.3 4
9.52
8.36
7.29
8.34
8.378
8.38
b) b)
8.4 0
8.3 5
8.4 2
8.3 6
8.40
8.35
8.42
8.36
8.383
8.38
c) c)
7.9 5
8.0 0
8.0 5
7.9 5
7.95
8.00
8.05
7.95
7.988
7.99
Averag e Avera ge
Roun d Off
Avera ge
Roun d Off
9.52
8.36
7.29
8.34
__ ____ ____
8.378
a) b) de vi atio n
-1.14
0.02
1.09
0.04
0.573
8.40
8.35
8.42
8.36
__ ____ ____
8.383
c) de vi atio n
-0.02
0.03
-0.04
0.02
0.028
7.95
8.00
8.05
7.95
__ ____ ____
7.988
de vi atio n
0.0 4
-0.0 1
-0.0 6
0.0 4
0.038
8.38 +/- 0.57
8.38 +/- 0.0 3
Abs olute va lue ( all of the - becom e +)
7.99
+/- 0.04

QUESTION
The melting point of pure benzoic acid is 122 ° C. Data obtained by four students in a laboratory experiment are shown below. Which student’s data are precise but not the most accurate?
A) Student A
C) Student C
B) Student B
D) Student D

Answer
The melting point of pure benzoic acid is 122 ° C. Data obtained by four students in a laboratory experiment are shown below. Which student’s data are precise but not the most accurate?
A) Student A
C) Student C
B) Student B
D) Student D

(Average Deviation vs. Standard Deviation) http://en.wikipedia.org/wiki/Standard_deviation
The distribution of data (individual data points) in a set is not considered by the Average Deviation. Standard
Deviation, which is the square root of the data set’s variance relative to its average (mean), is commonly used to do this.

(Standard Deviation) http://en.wikipedia.org/wiki/Standard_deviation
Standard Deviation is the square root of the data set’s variance relative to its average (mean). Mathematically:
Where σ is the Standard Deviation, μ is the data’s average (mean), N is the total number of data points, and x i is the individual data point.

Provide the Standard Deviation
(The Following Measured Data is for Volume in mL)
Standard deviation
+/- 0.91
+/- 0.57
(Avg. Dev)
Standard deviation
+/- 0.03
+/- 0.03
(Avg. Dev)
Standard deviation
+/- 0.05
+/- 0.04

Example: Chem 120 VAT Survey Results
What number best represent the respective
VAT class result?
Average of each.
A
28
24
20
30
28
6
26
26
24
22
34
22
28
26
32
30
32
22
26
24
22
26
12
30
22
28
22
26
22
28
26
26
24
28
22
22
22
28
30
26
30
32
21
24
22
14
28
32
28
24
24
20
30
24
24
30
22
26
28
28
V
34
34
34
30
32
35
36
30
28
30
28
28
30
32
36
26
30
36
28
22
32
32
30
28
28
26
30
22
30
28
32
28
32
34
26
38
32
30
32
32
26
28
22
38
32
36
34
34
32
30
24
32
34
40
25
32
34
34
34
28
T
28
26
26
24
35
34
28
22
16
28
18
23
18
22
30
18
15
32
22
28
18
26
38
30
30
30
14
22
26
32
28
38
28
24
20
24
24
21
32
24
26
16
30
32
24
26
28
24
23
20
22
24
18
22
26
38
24
22
14
16
How much does the class vary in each?
Standard
Deviation of each,
Maximum &
Minimum of each.

Example: Chem 120 VAT Survey Results
AVG
STDev
Max
Min
V
31
4
40
22
A
25
5
34
6
T
25
6
38
14
Can you use a spreadsheet?

QUESTION
Rank the relative precision of the three sets of data: a), b) and c). The accepted value is 8.08 mL.
Average a)
8.38
Average b)
8.38
Average c)
7.99
Standard deviation a)
+/- 0.91
A) Precision: a > c > b
C) Precision: a = b > c
Standard deviation b)
+/- 0.03
Standard deviation c)
+/- 0.05
Answer:
B) Precision: b > c > a
D) Precision: a > b > c

QUESTION
Rank the relative accuracy of the three sets of data: a), b) and c). The accepted value is 8.08 mL.
Average a)
8.38
Average b)
8.38
Average c)
7.99
Standard deviation a)
+/- 0.91
A) Accuracy: a > c > b
Answer:
C) Accuracy: c > a = b
Standard deviation b)
+/- 0.03
Standard deviation c)
+/- 0.05
B) Accuracy: b > c > a
D) Accuracy: a = b > c

Density
Density = Mass / Volume [ g/mL or g/cm 3 ; g/L ]
Refer to Lab Manual/Worksheets
•
One of the densest substances: a White Dwarf http://antwrp.gsfc.nasa.gov/apod/ap961203.html
1.0 teaspoon = 3.0 T (metric tons);
Calculate its density:
D = ? g/cm 3
(1 tsp = 4.93 mL; 1 mL = 1 cm 3 ; 1 metric ton =
1,000 kg )
D = ? g/cm 3

Density
Density = Mass / Volume [ g/mL or g/cm 3 ; g/L ] (k g/m 3 )
Refer to Lab Manual/Worksheets
White Dwarf http://antwrp.gsfc.nasa.gov/apod/ap961203.html
D = 610,000 g/cm 3 ( 6.1 x 10 5 g/cm 3 )
A White Dwarf’s mass is comparable to our Sun's, but its volume is about a million times smaller; the average density is ~1,000,000 times greater than the Sun’s, approximately 1 x 10 6 g/cm 3
Our Sun will eventually become a white dwarf
“butterfly”….. but not for
~5 billion years.

Density
Density = Mass / Volume [ g/mL or g/cm 3 ; g/L ]
Refer to Lab Manual/Worksheets
White Dwarf http://antwrp.gsfc.nasa.gov/apod/ap961203.html
D = 610,000 g/cm 3 ( 6.1 x 10 5 g/cm 3 )
Density astro
= ? kg/m 3
The density of a Neutron star (pulsar) is
3.7
× 10 17 to 5.9
× 10 17 kg/m 3 (~ 3 × 10 14 times the density of our Sun)
How many times denser a Neutron Star versus a
White Dwarf?

Density
Density = Mass / Volume [ g/mL or g/cm 3 ; g/L ]
Refer to Lab Manual/Worksheets
•
One of the least dense man-made solid substances: Aerogel http://eetd.lbl.gov/ECS/aerogels/aerogels.htm
http://stardust.jpl.nasa.gov/spacecraft/aerogel.html
•
PS 275 has a volume of ~220 yd 3 .
•
When filled with Aerogel, the total weight of Aerogel is
• ~ 1100 lbs. What is the density of Aerogel?
D = ? g/cm 3
•
D = 3.0 x 10 -3 g/cm 3
D = ? g/L

Density
Density = Mass / Volume [ g/mL or g/cm 3 ; g/L ]
Refer to Lab Manual/Worksheets
•
Aerographite is a synthetic foam consisting of a porous interconnected network of tubular carbon. It was first reported by researchers at the University of Kiel and the Technical University of
Hamburg in Germany in a scientific journal in June 2012. It’s density is:
•
D = 0.00112 lbs/ft 3
•
Which is less dense Aerogel or
Aerographite?
•
D = ? g/cm 3

QUESTION
A metal sample is hammered into a rectangular sheet with an area of 31.2 ft 2 and an average thickness of
2.30 × 10
−6 cm. If the mass of this sample is 0.4767 g, predict the identity of the metal.
The density of the metal is shown in parenthesis.
Useful information: 1 in = 2.54 cm
A) Aluminum (2.70 g/cm 3 ) B) Copper (8.95 g/cm 3 )
C) Gold (19.3 g/cm 3 ) D) Zinc (7.15 g/cm 3 )

Answer
A metal sample is hammered into a rectangular sheet with an area of 31.2 ft 2 and an average thickness of
2.30 × 10
−6 cm. If the mass of this sample is 0.4767 g, predict the identity of the metal.
The density of the metal is shown in parenthesis.
Useful information: 1 in = 2.54 cm
A) Aluminum (2.70 g/cm 3 ) B) Copper (8.95 g/cm 3 )
C) Gold (19.3 g/cm 3 ) D) Zinc (7.15 g/cm 3 )

Density
Density = Mass / Volume [ g/mL or g/cm 3 ; g/L ]
Refer to Lab Manual/Worksheets
•
How many pounds of air are there in PS 275?
It has a volume of ~220 yd 3 .
•
D air
•
= 1.22 x 10 -3 g/cm 3 (1.22 g/L)
•
Mass = Density x Volume
Mass = 450 lbs

What number best represent the respective
VAT class result?
Average of each.
A
28
24
22
26
24
22
6
22
28
26
32
30
32
26
26
20
30
28
24
22
34
30
22
28
22
26
12
30
26
22
28
26
21
24
22
22
22
26
24
28
28
30
26
24
24
22
14
28
32
24
32
28
26
28
28
24
30
22
20
30
T
18
23
18
32
22
28
22
30
18
15
34
28
26
26
24
22
28
18
35
16
28
26
30
30
14
26
38
30
22
26
32
28
30
32
20
24
24
38
28
24
21
32
24
20
22
24
26
28
16
22
24
23
22
14
16
26
38
24
24
18
V
34
34
36
28
22
32
35
28
30
32
36
26
30
36
30
34
30
32
28
30
28
26
28
26
30
32
30
28
22
30
28
32
22
38
26
38
32
28
32
34
30
32
32
30
24
32
36
34
28
40
34
32
34
34
28
25
32
34
32
34
How much does the class vary in each?
Standard
Deviation of each,
Maximum &
Minimum of each.

Chem 120 VAT Survey Results
AVG
STDev
Max
Min
V
31
4
40
22
A
25
5
34
6
T
25
6
38
14
Should V=40 and A=6 be eliminated from the Data set and the Average recalculated?

METHOD 3: METHOD 1:
Stack of 10 Pennies
Height Diameter
(mm) (mm)
13.1
17.1
NEW or OLD?
Mass
(g)
19.7483
Density g/cm3 DEV
Indivdual Penny
Height
(mm)
1.2
Diameter
(mm)
18.9
NEW or OLD?
Mass
(g)
2.0085
Density g/cm3 DEV
6.0215
6.6985
6.6905
6.3495
6.6806
6.0294
6.8811
6.3789
6.0800
6.3016
6.8984
7.0055
7.7045
5.7002
6.1998
6.0008
5.7992
7.5000
Working Calculated Average Working Calculated Average
REPORTED AVERAGE
AVG DEV.
STD DEV
ACCURACY
Correct # of significant digits
%
REPORTED AVERAGE
AVG DEV.
STD DEV
ACCURACY
Correct # of significant digits
%
METHOD 2:
Stack of 10 Pennies
Volume
(mL)
4.1
NEW or OLD?
Mass
(g)
29.5854
Density g/cm3
7.6015
7.0585
7.9802
7.7998
7.3600
7.1006
7.0100
7.0194
7.8600
Working Calculated Average
REPORTED AVERAGE
AVG DEV.
STD DEV
ACCURACY
DEV
Correct # of significant digits
%
METHOD 4:
Indivdual Penny
Volume
(mL)
0.35
NEW or OLD?
Mass
(g)
2.6525
Density g/cm3
9.2008
6.8992
7.9805
7.1995
6.7122
6.1878
7.0100
6.3005
8.8995
Working Calculated Average
REPORTED AVERAGE
AVG DEV.
STD DEV
ACCURACY
DEV
Correct # of significant digits
%
Q-Test, Standard Deviation & 10% Test (Avg. Dev.)

QUESTION
Which would provide more grams of NaCl, sample one with a mass of 2,350 mg, or sample two, a solid with a volume of 2.00 cm 3 ? (The density of solid salt is 2.16 g/cm 3 .) Select the most massive sample and its mass in grams.
A. Sample two; 1.08 grams
B. Sample two; 4.32 grams
C. Sample one; 2.35 grams
D. Sample one; 2.350 grams

Answer
Which would provide more grams of NaCl, sample one with a mass of 2,350 mg, or sample two, a solid with a volume of 2.00 cm 3 ? (The density of solid salt is 2.16 g/cm 3 .) Select the most massive sample and its mass in grams.
A. Sample two; 1.08 grams
B. Sample two; 4.32 grams
C. Sample one; 2.35 grams
D. Sample one; 2.350 grams
The mass of sample two is obtained from its density and volume by multiplying 2.00 cm 3 × 2.16 g/cm 3 .

QUESTION
The volume of any material can be obtained from its density and mass.
If the mass of a sample of acid from a battery were 5.00 grams and its density was 1.2 g/mL, what would the correct reported volume in mL with the proper number of significant digits?
A. 6.0 mL
B. 6.00 mL
C. 4.2 mL
D. 4.17 mL

Answer
The volume of any material can be obtained from its density and mass.
If the mass of a sample of acid from a battery were 5.00 grams and its density was 1.2 g/mL, what would the correct reported volume in mL with the proper number of significant digits?
A. 6.0 mL
B. 6.00 mL
C. 4.2 mL
D. 4.17 mL
Volume from mass and density is V = m/D. Significant digits in the answer, which involves division in the calculation, is limited to the same number of significant digits as the least number in any of the values used in the calculation.