Chem2 help

2 parts:

1. Data and Results page (Use images to fill in the data) 

2. M2 post lab assignment

Material for study is attached.

Check link: http://stemtransfer.org/resources/competencies/sigfigs/ before doing the work

Need it in 24 hours, by 7am PST on 20th Feb

Appendix1

SIGNIFICANT FIGURES

A-1

Part I: Reading Measuring Devices

When you measure an object with a ruler such as Ruler I shown in the figure below, you
know for sure that its length is somewhere between 6.2 and 6.3 cm. To figure what digit
should come after the 2, you visually divide up the space in ten parts and note the
approximate location of the right edge of the object. Because the right edge appears to be
about 6/10th of the way between the 0.2 and the 0.3 marks, we would say that the length is
6.26 cm. If someone else reports the measurement as 6.27 cm, that would also be acceptable.
It is understood that the last digit reported always has some uncertainty. We call these three
digits significant figures. Significant figures are digits that are of significance—they are all
the accurately known digits plus the first uncertain digit in a measurement. They tell us
how finely graduated the measuring device is. The more finely the graduation, the more
reproducible the results would be, and therefore the more precise the measurement is. By
reporting the length as 6.26

cm

(2 decimal places), you are telling someone that the smallest
divisions on the ruler are 0.1 cm apart and that the last digit is uncertain.

Ruler I

In comparison, when you measure the same object with Ruler II, which is graduated only to
1 cm, you only know for sure that the length is somewhere between 6 and 7 cm. The next
digit you read is an estimate. So, you might read it as 6.2 cm, but you cannot report it as
6.20 or 6.25 cm. By reporting 6.2 cm, you are telling someone that the smallest divisions on
the ruler are 1 cm apart and that the last digit is your best estimate of reading between the 6
cm and 7 cm marks.

The general rule is therefore, to read a measurement to one-tenth of the smallest division on
the measuring device. That is, you should add one more digit than can be read directly from
the calibration marks. For Ruler I, the smallest division is 0.1 cm and so you read
measurements to two decimal places. For Ruler II, the smallest division is 1 cm and so you
read measurements to one decimal place. Keep this in mind whenever you make a
measurement with equipment (such as rulers, graduated cylinders and burets) that does not
give you a digital display (such as an electronic balance or temperature probe). When using
a digital display, you must record all the digits displayed—they are all significant.

Learning to read measuring devices properly is very important for laboratory work. To
check your understanding, do the following practice exercise.

cm Ruler II

cm

Appendix 1: SIGNIFICANT FIGURES

A-2

Practice Exercise 1
Write your answers on the blanks, then check them against answers provided at the end of
this appendix.

1.1) Record the measurements to the correct significant figures. Don’t forget your units!
A B C D

A = __________ B = __________ C = __________ D = __________

1.2) E F G H

E = __________ F = __________ G = __________ H = __________

1.3) I J K L

I = __________ J = __________ K = __________ L = __________

Part II: Identifying Significant Figures in Numbers

There are various methods to determining which digits in a given number are “significant,”
but ultimately they all point to the same answer. Your textbook may tell you one method,
and your instructor may tell you another. You are likely to find that the method shown
below is the simplest to remember.
The general rule is as follows:

All digits in a measurement are significant with the exception that:
1. leading zeroes are NEVER significant (0.0005 has only one sig. fig.)
2. tailing zeroes in numbers without decimal points are ambiguous. (Zeroes in

700 are ambiguous. Zeroes in 700.0 are significant.)
• Such tailing zeroes are generally assumed to be not significant.
• They can be expressed in scientific notation to remove the ambiguity.

| | | | cm

| | | | cm

in | | | |

Appendix 1: REVIEW OF TREATMENT OF SIGNIFICANT FIGURES

A-3

For example, 5200 as stated is assumed to have 2 sig. figs.
If it were to have 3 sig. figs., it should have been expressed as 5.20 x 103.
If it were to have 4 sig. figs., it should have been expressed as 5.200 x 103, or it could
have been expressed as 5200. with the decimal point after the last zero. This indicates that
the tailing zeroes are significant. (Remember tailing zeroes are assumed not significant
only when there is no decimal point. Tailing zeroes in numbers with decimal points are
significant.)

In the following examples, the significant figures are underlined.

30 is assumed to have one sig. fig.
30. has 2 sig. figs. (The number has a decimal point, so all tailing zeroes are significant.)
30.0 has 3 sig. figs. (Again, the number has a decimal point, so all tailing zeroes are

significant.)
0.0050200 has 5 sig. figs. (Leading zeroes are not significant, but the tailing zeroes are

significant, because the number has a decimal point.)
12.00 has 4 sig. figs.
3.20 x 102 has 3 sig. figs.

Do not confuse the number of significant figures with the number of decimal places. The
number of decimal places refer to the number of digits to the right of the decimal point.
Thus 30.0 has three sig. figs. but only one decimal place. The practice exercise below
provides opportunity for you to distinguish between the number of significant figures and
the number of decimal places in a number. It also provides the opportunity to distinguish
between zeroes that are significant and those that are not significant.

Practice Exercise 2
2.1) Give the number of sig. figs. and the number of decimal places in each of the number

below.
# sig. figs. # decimal places # sig. figs. # decimal places

12.92 _______ ______________ 8,000 _______ ______________
30.009 _______ ______________ 8,000. _______ ______________
0.005 _______ ______________ 8,000.00 _______ ______________
0.00260 _______ ______________

2.2) These numbers have ambiguous zeroes. Express them in scientific notation to remove

the ambiguity.

35000 in 2 sig. figs. ______________ 1800 in 3 sig. figs. ______________
35000 in 3 sig. figs. ______________ 680,000 in 4 sig. figs. ______________
35000 in 4 sig. figs. ______________ 2700 x 10-8 in 3 sig. figs. ______________

Appendix 1: SIGNIFICANT FIGURES

A-4

Part III: Using Scientific Notation

A number should be expressed in scientific notation (with only one nonzero digit to the left
of the decimal) under these conditions:

1. A number with ambiguous zeroes (tailing zeroes in a number without a decimal)
To remove the ambiguity, it can be expressed in scientific notation.
e.g. It is not clear whether 35000 has 2, 3, 4 or 5 sig. figs. It is not clear whether the
three “tailing zeroes” are significant or not. Suppose you mean 35000 to have 3 sig.
figs., then it should be expressed as 3.50 x 104.

2. A number that is very small (as a rule of thumb, less than 0.01).

It is tedious and riskier to copy numbers with a string of avoidable zeroes.
e.g. 0.000 000 83 should be expressed as 8.3 x 10−7

3. A number that is in exponential form for any reason

e.g. 324.3 x 10−8 should be expressed as 3.243 x 10–6

Some students indiscriminately express all their numbers in scientific notation. Although it
is not “wrong” to do so, you should learn when it is appropriate. For example, it would not
be appropriate to tell someone to weigh out “2.5 x 10 grams of salt” when “25 grams of salt”
would do equally well.

20.0 x 5.0 = 100
This should be expressed as 2 sig. figs. Because the tailing zeros are ambiguous, the
number should be expressed in scientific notation.
Correct answer = 1.0 x 102

0.004 ÷ 800 = 0.000005
This should be expressed as 1 sig. fig. Because there are so many leading zeros, the
number can be expressed in exponential notation.
Correct answer = 5 x 10−6

(42 x 10 3) x 2 = 84 x 103
This should be in 1 sig. fig. and being a very large number, needs to be in scientific
notation.

Correct answer = 8 x 104

22 x 2.0 = 44

This should be in 2 sig. figs. There is nothing wrong with the way it is stated.
Correct answer = 44

The following practice exercise provides an opportunity for you to check your
understanding of when to use scientific notation.

Appendix 1: REVIEW OF TREATMENT OF SIGNIFICANT FIGURES

A-5

Practice Exercise 3
3.1) Which of the following numbers require scientific notation? For any that require it,

give the correct way of expressing it.
A. 350 cm B. 0.13 g C. 38 mL D. 0.00032871 E. 235.2 x 104

3.2) Convert the following numbers from scientific notation to standard notation.

A. 1.5 x 104 B. 4.59 x 10-7

Part IV: Rounding-off Numbers

In correcting a number to express the proper number of sig. figs., we often have to drop off
unwanted digits. The rules for rounding off numbers are explained in your textbook and/or
lab manual. Here is a summary:

Rules for rounding off numbers:

If the digit immediately to the right of the last sig. fig. is equal or greater than 5, you
round up.
If the digit immediately to the right of the last sig. fig. is less than 5, you round down.

For example,
72.49 in 3 sig. figs. is 72.5
45.52 in 3 sig. figs. is 45.5
299 000 in 2 sig. figs. is 300000 and to remove ambiguity, the answer is 3.0 x 105
92528 in 4 sig. figs. is 92530 and to remove ambiguity, answer is 9.253 x 104

The practice exercise below provides an opportunity to check your understanding of
rounding.

Practice Exercise 4
4.1) Round the following numbers to the specified significant figures:

A. 26000 to one sig. fig.

Ans. _____________

B. 3510 to two sig. figs. Ans. _____________
C. 0.00375 to two sig. figs. Ans. _____________
D. 0.002787 x 103 to three sig. figs. Ans. _____________

4.2) A student was given the numbers in column A and asked to round them off to three
sig. figs. The student’s answers are in column B. Indicate whether the student’s
answers are correct or incorrect. If incorrect, give the correct answer.
Column A Column B Correct or Incorrect?
4925 493
0.0006399 0.0006400
535.456 535.000

Appendix 1: SIGNIFICANT FIGURES

A-6

Part V: Handling Significant Figures in Calculations

Rule 1: During Addition or Subtraction, the answer has the same number of decimal
places as the measurement with the least number of decimal places.

e.g. 3.255 3 decimal places

+ 1.76 2 decimal places
5.015 (should have only 2 decimal places)

= 5.02

Rule 2: During Multiplication or Division, the answer has the same number of sig. figs. as
the measurement with the least number of sig. figs.
e.g. 3.5 x 2.78 = 9.73 = 9.7

(2 sig. figs.) (3 sig. figs.) (should have 2 sig. figs.)

e.g. 4.00 x 3.0 = (2 sig. figs.)
2.00

Rule 3: When Addition, Subtraction, Multiplication, or Division are mixed together,
apply rules 1 and 2 one step at a time. This is very tricky, so think through this very
carefully.
e.g. 4.05 − 4.00 = 0.05 = 0.025 = 0.03
2.00 2.00
Count 1 sig. fig. for the division
2 decimal places for the subtraction

Rule 4: When there are several steps before you get to the final answer, carry one extra
digit and round off properly at the end. You can keep track of where the last digit should be
by placing a line under the digit in that position. Or, we can keep track of the extra digit by
writing a line through it.
e.g. 78.2 + 5.23 = ?
21.3 3.4

= 3.671 + 1.54

= 5.211 = 5.2 (limiting answer to one decimal place in the addition)

6.0

Appendix 1: REVIEW OF TREATMENT OF SIGNIFICANT FIGURES

A-7

Rule 5: Keep in mind that you cannot get more precision just by doing a calculation such as
finding the average of several numbers. The average must have the same number of decimal
places as the individual numbers themselves.
e.g. The average of 37 and 38 mathematically comes out to 37.5, but as written the
average would have more digits than 37 and 38. The correct answer is 38 (37.5 rounded off.)

Practice Exercise 5
Provide answers for the following computations.

5.1) 69.76
– 65.2
Ans. _____________

5.2) 9.21
+ 7.242
Ans. _____________

5.3) 21 x 3 =
Ans. _____________

5.4)
5.0 + 3.0

=
2.00

Ans. _____________

5.5)
33.9 – 32.1

=
2.00
Ans. _____________

5.6) Find the average of 73.2, 73.8 and 74.2. Ans. _____________

5.7) Find the average of 82.3 and 82.4. Ans. _____________

Part VI: Calculating with Exact Numbers

Certain types of numbers are considered “exact.” For example, there are exactly 16 ounces
in one pound. The number 1 and the number 16 would have an unlimited number of
significant figures. So one pound (1.00000000000…), for example, has 16.000000000000….
ounces. Calculations involving these number should not be limited by the significant figures
shown in “16 oz/lb.” If we want to calculate how many ounces are in 2.00 lb, for example,
we would set up the problem thus:

2.00 lb x
16 oz

= 32.0 oz
1 lb

Appendix 1: SIGNIFICANT FIGURES

A-8

The answer has 3 sig. figs. even though 1 appears as 1 sig. fig. and 16 appears as 2 sig. figs.
The answer is limited by 2.00 lb (3 sig. figs.) and not by 1 or 16 because they are “exact”
numbers.

Which types of numbers are considered “exact?” Below are the general rules.
1. Conversions between units within the English System are exact.
e.g. 12 in. = 1 ft or 12 in./1 ft (12 and 1 are both exact.)

2. Conversions between units within the Metric System are exact.
e.g. 1 m = 100 cm or 1 m/100 cm (1 and 100 are both exact.)

3. Conversions between English and Metric system are generally not exact. Exceptions will

be pointed out to you.
Example of an exception: 1 in. = 2.54 cm exactly (Both 1 and 2.54 are exact.)

Example of general rule: 454 g = 1 lb or 454 g/1 lb (454 has 3 sig. fig., but 1 is
exact.)

4. “Per” means out of exactly one.

e.g. 45 miles per hour means 45 mi = 1 hr or 45 mi/1 hr. (45 has 2 sig. fig. but 1 is
exactly one.)

5. “Percent” means out of exactly one hundred.

e.g. 25.9% means 25.9 out of exactly 100 or 25.9/100. (25.9 has 3 sig. fig., but 100 is
exact.)

6. Counting numbers are exact. Sometimes it is hard to decide whether a number is a

“counting number” or not. In most cases it would be obvious. Ask when in doubt.
e.g. There are 5 students in the room. (5 would be an exact number because you cannot

have a fraction of a student in the room.)
e.g. Find the average of 3.27 and 3.87. (To find the average, you add the two numbers

together and divide by 2. “2” is an exact number. Do not round your average to 1
sig. fig.)

Appendix 1: REVIEW OF TREATMENT OF SIGNIFICANT FIGURES

A-9

Answers to Practice Exercises

Practice Exercise 1

A = 1.64 cm B = 3.04 cm C = 5.00 cm D = 8.97 cm
E = 0.2 cm F = 2.9 cm G = 6.0 cm H = 8.3 cm
I = 0.602 in. J = 0.696 in. K = 0.794 in. L = 0.822 in.
Because the last digit in any measurement should be an estimate, your measurements
can be different in the last digit.

Practice Exercise 2
2.1) sig. fig. # decimal places # sig. fig. # decimal places

12.92 ___4___ _____2________ 8000 assume 1 _____none_____
30.009 ___5___ _____3________ 8000. ___4___ _____none_____
0.005 ___1___ _____3________ 8000.00 ___6___ _______2______
0.00260 ___3___ _____5________

2.2) These numbers have ambiguous zeroes. Express them in scientific notation to remove

the ambiguity.

35000 in 2 sig. fig. ___3.5 x 104____ 1800 in 3 sig. fig. __1.80 x 103____
35000 in 3 sig. fig. ___3.50 x 104___ 680,000 in 4 sig. fig. __6.800 x 105___
35000 in 4 sig. fig. ___3.500 x 104__ 2700 x 10-8 in 3 sig. fig. __2.70 x 10−5___

Practice Exercise 3
3.1) A = 3.5 x 102 cm D = 3.2871 x 10−4 E = 2.352 x 106

B and C do not require scientific notation.

3.2) A. 1.5 x 104 = 15000 (2 sig. figs) B. 4.59 x 10-7 = 0.000000459

Practice Exercise 4
4.1) A = 3 x 104 B = 3.5 x 103 C = 3.8 x 10−3 D = 2.79

4.2)
Column A Column B Correct or Incorrect?
4925 493 Incorrect, 4.93 x 103
0.0006399 0.0006400 Incorrect, 6.40 x 10-4

535.456 535.000 Incorrect, 535

Practice Exercise 5

5.1) 4.6 5.2) 16.45 5.3) 6 x 101 5.4) 4.0 5.5) 0.90
5.6) 73.7 5.7) 82.4

Appendix 1: SIGNIFICANT FIGURES

A-10

Experiment 2: MEASUREMENT

1

Purpose: To learn how to properly use common laboratory measuring devices, to learn
the difference between accuracy and precision in measurement, and to compare the
reliability of measuring versus estimating.

Introduction
Have you ever watched a cooking show on television and noticed the chef mixing
ingredients without measuring? Well, he is probably able to do that because of years of
experience. If you were required to do an experiment that calls for specific amounts of
various chemicals, could you, like the chef, estimate well the amount of each chemical and
get a good result? Unlikely! When it comes to cooking, a little less or more of an ingredient
might not even be noticed but for chemistry, the amount matters. And because the amount
matters when doing scientific work, chemists generally do not estimate the amount of the
chemicals they use in sensitive experiments but instead they make careful measurements.

Measurement is considered to be the foundation of modern chemistry. It is a foundation that
was laid by scientists such as Antoine Lavoisier (1743-1794) who was able to make careful
measurements that lead to the formulation of the law of conservation of mass. For his work,
Lavoisier had acquired a sophisticated balance that was sensitive enough to detect the
changes in mass during his experiments. Still, any measuring device, whether sophisticated
or simple, has limitations, which affect the accuracy of the measurements that can be made
using it.

Accuracy and Precision
Because all measuring devices have limitations, any measurement made with a laboratory
tool has an experimental uncertainty associated with it. Therefore, whenever a scientist
records a measurement, it is important to convey how reliable it is, that is, how accurate or
precise that measurement is. By accuracy, we mean how close the experimentally measured
value is to the correct or true value. The term precision, on the other hand, means how
reproducible the experimentally measured values are. That is, if we were to measure the
same object several times, precision is how close those experimental values are to each
other. To some extent this depends on the expertise of the person doing the measurement,
and on the method of measurement, but the type of apparatus being used can also limit the
precision of the measurement. To provide information about the accuracy of a
measurement, the percent error is generally calculated and reported.

Error = experimental value − true value

Percent Error = !””#”

!”#$ !”#$%
x 100

A positive error or percent error tells us that the experimental value is too high. A negative
value tells us that the experimental value is too low. The size of the error depends on a
number of factors but suffice it to say that a small percent error, say between 0 and 5% is
acceptable for many chemistry experiments and indicates good accuracy.

Experiment 2: MEASUREMENT

2

Precision is determined by the deviation of the experimental value from the average value
(rather than the true value). In this course you will not be asked to calculate the deviation.
However you should be aware of the difference between accuracy and precision. We will
concentrate on how the apparatus affects the precision of measurement. To convey
precision, the experimental value should be recorded to the correct significant figures.

Location of the Uncertain Digit in a Measurement
Information concerning the experimental uncertainty associated with measurements made
using a particular tool can be obtained by examining the calibrations marked on it. In
making a measurement a scientist always reads and records all the digits which can be read
directly from the tool plus one additional digit which represents his or her estimate in
reading between the calibration lines. This last digit is what is called the uncertain digit.
Thus, a correctly determined measurement from a particular tool contains all the digits one
is sure of plus a final digit that is the scientist’s best estimate between lines. This is true for
all measurements made with tools that are marked with calibration lines. If however, the
measuring device displays the measured value (as is the case with electronic balances); all
the digits displayed must be recorded. For the displayed value, the uncertain digit is the
rightmost digit. Thus, all measured values—whether figured-out by an experimenter or
displayed by a device—must contain one uncertain digit. All the certain digits along with the
one uncertain digit in a measurement are called significant figures or significant digits.

In this experiment we will concentrate on how the apparatus affects the precision of a
measurement. To convey precision, the experimental value should be recorded to the
correct number of significant figures. The general rule is to record all measurements to
one-tenth of the smallest division on the measuring device. Table 2.1 shows the size of
the smallest divisions on a measuring device and the number of decimal places expected in a
measurement made with that device.

Table 2.1 Divisions on Measuring Scales and Expected Decimal Places in Measurements
Size of Smallest
Divisions on a
Measuring Device

!
!”

of Smallest Division # Decimal Places
in Measurement

Place Value of
Last Significant
Digit

1000 100 none hundreds
100 10 none tens
10 1 none ones
5 0.5 1 tenth
2 0.2 1 tenth
1 0.1 1 tenth

0.5 0.05 2 hundredth
0.2 0.02 2 hundredth
0.1 0.01 2 hundredth
0.01 0.001 3 thousandth

It is important to note that a more precise measuring device can be used to make
measurements requiring less precision but a less precise measuring device cannot be used to
make a more precise measurement. For example, to measure 25.0 mL of a liquid, we could

Experiment 2: MEASUREMENT

3

use a 50-mL buret with 0.1 mL divisions as well as a 50-mL or 100-mL graduated cylinder
with divisions of 1 mL. What we could not use is a 50-mL beaker with divisions of 10 mL.
The buret would give 25.00 mL; the graduated cylinder would give 25.0 mL; and the beaker
would give 25 mL. Since the 2 and the 5 must be certain, the beaker could not be used
because the 5 is an uncertain digit in the measurement made with the beaker.

Making Measurements Using various Measuring Devices
In this experiment you will use a variety of commonly used laboratory tools to measure
length, volume, and mass. As described below, each measuring device must be handled
properly and read correctly. (See also Appendix 1 that deals with significant figures.)

Length: Length can be measured with a ruler. The size of the calibration marks on the ruler
determines the number of decimal places in each length measurement. Consider the ruler in
Figure 2.1, for example. The smallest division of this ruler is 0.1 cm. Because you record
the length as one-tenth of 0.1 cm, which would be 0.01 cm (to 2 decimal places), you can
see the length of the object below could be read as 4.83 cm or 4.84 cm. The last digit we
should record is by estimating how far the object extends between 4.8 and 4.9 cm.
Obviously there is some uncertainty as to what that last digit might be. One might see it as
4.83 cm; another, as 4.84 cm.

Using the ruler pictured in

Figure 2.2

below, one could read the length of the same object as
being 4.8 cm or 4.9 cm. For this ruler, the smallest division is 1 cm, and one-tenth of 1

cm

is 0.1 cm. This means you can record only to one decimal place.

Volume: Volumetric wares are designed to contain (TC) or to deliver (TD) a certain volume
of a liquid. You can find these letters stamped on the container. It is important to use the
appropriate container for best results. Some volumetric wares also provide information
about the tolerance. The tolerance is the allowed deviation of the measuring device. The
tolerance is generally printed on the measuring device as a ± value. For example, on a 10-
mL volumetric flask you might see ±0.08 mL meaning that when the flask is filled, the
volume could be any value between 9.92 mL and 10.08 mL. The volume should therefore be
written as 10.00 ± 0.08 mL.

The graduated cylinder is generally used for measuring the volume of a liquid. In a narrow
tube such as a graduated cylinder or a buret, many liquids such as water and aqueous
solutions have a curved surface called a meniscus. The proper way to measure the volume

cm

Figure 2.1

cm
Figure 2.2

Experiment 2: MEASUREMENT

4

of such a liquid is to read the bottom of the meniscus at eye-level as shown in Figure 2.3.
This is easier said than done with water being colorless. For this reason you will prepare a

Volume-Reading Card

to make the bottom of the meniscus more visible.

Figure 2.3

It is important to note that for most volume measurements only one reading of volume is
required. However, when using the buret to measure volume, two readings are required—an
initial reading and a final reading. The volume dispensed is determined by taking the
difference between them.

Volume dispensed from buret = final buret reading – initial buret reading

Mass: Mass is measured with a balance. Some balances have to be read manually but the
balances used in this experiment are electronic balances and they are designed to display the
masses for you. The last digit in a displayed mass is the uncertain digit in that mass
measurement. And, because all measurements should have one uncertain digit, it means that
all of the digits displayed on the balances are significant and should be recorded.

The use of the electronic balance is simple. Generally, a substance to be weighed is placed
in the container in which it will be used and weighed with the container. This method of
weighing is called weighing by difference and it is generally a more accurate way of
weighing than weighing directly. To get the mass of the substance, the empty container is
weighed first. Next the substance is placed in it and the two are weighed together. Finally,
the mass of the empty container is subtracted from the mass of the container and substance.
Figure 2.4 shows diagrams of two kinds of balances you are likely to use.

Always remember to read
the meniscus at eye-level.

Volume-Reading Card

Experiment 2: MEASUREMENT

5

Figure 2.4

In addition to paying attention to the significant figures, you must learn to always convey
what units you are using. For example, if you are measuring dimensions with a ruler, you
need to specify whether you are measuring in inches, centimeters, millimeters, or some other
unit. It is gross carelessness to leave off the units of a measurement. And in real life
situations, such carelessness could lead to loss of lives and property.

Equipment/Materials
Metric ruler, index card, black marker, 50-mL and 100-mL beakers, 50-mL buret, ring stand,
buret clamp, 100-mL volumetric flask, 25-mL pipet, pipet pump, 10-mL graduated cylinder,
50-mL graduated cylinder, 100-mL graduated cylinder, 100-mL plastic beaker, metal shots,
100-gram standard, electronic balance

Procedure
(Using a pen or pencil, record by hand all of your data and results and perform all
calculations on the Data Collection and Results Pages.)

I. Length Measurement
1. Obtain a metric ruler.
2. Note and record the size of the smallest divisions on the ruler.
3. Use the ruler to measure the length of Rod A below in cm.

Rod A

II. Volume Measurement
1. Preparation of the Volume-Reading Card: Obtain an index card. With a black marker,

draw a thick black line (about 1 cm thick) across the length of the card.

2.

Experiment 2: MEASUREMENT

6

3. Obtain the following volumetric wares: 50-mL beakers (2), 50-mL buret, 100-mL
volumetric flask, 25-mL pipet, 50-mL and 100-mL graduated cylinders. Make sure all
these items are clean and dry.

4. Examine each piece of glassware to determine whether it is designed as TC, TD, or both
TC and TD, or neither.

5. Note and record the size of the smallest division on each piece of glassware or the
tolerance.

Measuring with a beaker:

6. Pour tap water into one of the 50-mL beakers until the water level is somewhere between
the 30-mL and 40-mL marks. Read and record the actual amount of water in the beaker.

7. Transfer the water from the 50-mL beaker into the 50-mL graduated cylinder. Do your
best to transfer all of the water from the beaker to the graduated cylinder. Read and
record the amount of water in the graduated cylinder. Use your Volume-Reading Card to
help you see the meniscus more clearly.

Measuring with a buret:

8. Take the clean and dry 50-mL buret and pour tap water into it until it is filled. You may
need to use a filling funnel to help channel the water into the buret.

9. Set up the buret on a ring stand. Place a small beaker under the tip of the buret. Open
the valve at the bottom of the buret and allow the water to drain down until the bottom of
the meniscus is on the 1-mL mark. Make sure there are no air bubbles in the liquid. If
there are bubbles, drain some more of the water out of buret and fill the buret back up to
the 1-mL mark. Remove the filling funnel (if you had used one) and then read and record
the volume as initial buret reading.

10. Place a dry 50-mL graduated cylinder under the tip of the buret and drain the water
down until the level of the water in the buret is at the 26-mL mark. Read and record the
volume in the buret as final buret reading. Then, calculate the volume of water
dispensed from the buret. Next, read and record the volume of water collected in the
graduated cylinder.

Measuring with a pipet:

11. Pour tap water into the other 50-mL beaker up to about the 40-mL mark. Use the 25-mL
pipet to transfer 25 mL of the water from the beaker to a 50-mL graduated cylinder.
After the liquid is run out of the pipet, touch the tip of the pipet to the side of the
graduated cylinder to dislodge any adhering droplet and examine the pipet tip. You will
note that there is a tiny amount of the liquid remaining in the narrow tip. This is
supposed to remain in the tip. Do not blow this into your pipetted sample.

12. Read and record the volume of water in the graduated cylinder.

Experiment 2: MEASUREMENT

7

Pipetting with a pipet pump: To pipet a liquid, do the following:

i) make sure the plunger is all the way down into the barrel;
ii) insert the mouth of the pipet into the chuck with a slight rotating motion;

Warning: Be careful when placing a glass pipet into the pump. Glass
may break or shatter when forced.

iii) using your dominant hand, immerse the pipet tip beneath the surface of the
liquid in the beaker and roll the wheel to bring the plunger up and draw the
liquid into the pipet until the bottom of the meniscus is at the scratch mark on
the neck;

iv) remove the tip of the pipet from the liquid and place the tip over the container
that you are transferring the liquid to;

v) then roll the wheel in the opposite direction to bring the plunger down and
dispense the liquid or press the quick release lever to quickly dispense the
liquid.

Pipet Pump

Measuring with a volumetric flask:
13. Take the clean and dry 100-mL volumetric flask. Find and record the tolerance of the

flask. The tolerance is usually stamped on the bulb region of the flask.

14. Take a clean and dry 100-mL graduated cylinder and fill it with tap water to the 100-mL
mark.

15. Carefully transfer the water from the graduated cylinder to the 100-mL volumetric flask

using a small funnel. There should be no droplets of water remaining in the cylinder or
adhering to the neck of the funnel and volumetric flask. Note where the bottom of the
meniscus of the water is in relation to the scratch mark on the volumetric flask (that is,
at, above, or below the scratch mark).

III. Precision of Measuring Volumes
Effect of Eye-Level on Accuracy of Reading Volumes

1. Place exactly 7.00 mL of deionized water into a 10-mL grad cylinder. Use a
disposable pipet to help you add or remove excess water so that the bottom of the
meniscus is at exactly the 7-mL mark when held at eye-level.

plunger

thumb wheel

quick release lever

barrel

chuck with threaded collar

Experiment 2: MEASUREMENT

8

2. Hold the cylinder so that the meniscus is well above your eye-level. Record the
volume. (Remember to record to the correct sig. fig.)

3. Repeat with the cylinder at eye-level and below eye-level.
4. Calculate the error for each reading.

Precision of Volume Using Various Apparatus
1. Pour the 7.00 mL of deionized water from the 10-mL grad cylinder into your 50-mL

grad cylinder and record the volume as precisely as you can.
2. Pour the water from the 50-mL grad cylinder into your 50-mL beaker and record the

volume as precisely as you can. Take the time to figure out how many decimal
places you need to record.

IV. Mass Measurement

1. Obtain a plastic beaker or small plastic cup, 100-gram standard weight, and metal
shots.

2. Hold the empty plastic beaker or cup in one hand and the 100-gram weight in the
other hand.

3. Have someone add metal shots into the plastic beaker or cup while you try to use the
weight in the other hand to help you judge when the beaker and shots together are
about the same weight as the 100-gram standard.

4. Once you feel that the beaker with the shots is about 100 g, weigh it.
5. Switch with the other person and repeat.
6. For these data calculate the error and % error for each result.

Clean-up

1. Empty water from containers into the sink.
2. Pour the metal shot back into the containers.
3. Return all equipment and materials back to their original location.
4. Clean up your work area.
5. Wipe off and return the safety goggles to the cabinet (or place it in your drawer if

it belongs to you). Note that once you put away your safety goggles, you must
leave the lab. Remember to wash your hands before leaving.

Name __________________________

Module 2

Post-Lab Assignment

Short Answer (45 points)

Answer the following questions based on material covered in this module. (5 points each)

(You must use complete sentences when answering each question.

1-point deduction per question not answered in complete sentences.)

1) How many significant figures are in your cm measurement of Rod A? How did you figure out how many decimal places to use in your answer?

2) Could you use a 100-mL volumetric flask to measure 50.0 mL of a liquid? Explain.

3) Which types of measuring devices could you use to measure 50.0 mL of a liquid? Explain.

4) Chefs often estimate the amount of ingredients needed for a dish. Do you think it would be a good idea to estimate rather than weigh the amount of chemicals needed for an experiment? Explain.

5) When the meniscus is above eye-level, what is the sign of your error? (positive or negative)

6) When the meniscus is below eye-level, what is the sign of your error? (positive or negative)

7) What is the effect on the volume when reading the meniscus above eye-level? below eye-level?

8) Examine the data you have collected in this section. Of the three different types of apparatus used in Part III, which do you think would give you:

(a) the most precise measurement of volume?

(b) the least precise measurement?

9) Based on your results in Part IV of the experiment, what does the percent error in the masses of your samples tell you about the accuracy of estimating? Is it a good idea or bad idea? Explain.

Experiment 2
MEASUREMENT

1

Data Collection and Results Pages Name: __________________________

Date: ___________________

I. Length Measurement
Size of smallest division ____________
Length of Rod A ___________________

II. Volume Measurement

50-mL beaker:
TC, TD, Both or Neither ____________ Size of smallest division __________
50-mL buret:
TC, TD, Both or Neither ____________ Size of smallest division __________
50-mL graduated cylinder:
TC, TD, Both or Neither ____________ Size of smallest division __________
100-mL graduated cylinder:
TC, TD, Both or Neither ____________ Size of smallest division __________
25-mL pipet:
TC, TD, Both or Neither ____________ Tolerance __________
100-mL volumetric flask:
TC, TD, Both or Neither ____________ Tolerance __________

Measuring with a Beaker
Volume of water in 50-mL beaker ______________
Volume transferred from beaker in 50-mL graduated cylinder _______________

Measuring with a Buret
Initial buret reading _____________
Final buret reading ______________
Volume dispensed from buret ____________
Volume transferred from buret to 50-mL graduated cylinder ________________

Measuring with a Pipet
Volume of water in 25-mL pipet _____________________
Volume transferred to 50-mL graduated cylinder _________________________

Measuring with a Volumetric Flask
Tolerance of 100-mL volumetric flask _________________________________
Volume of water in 100-mL graduated cylinder __________________________
Is the bottom of the meniscus at, above, or below the line on the flask? ________

Experiment 2: MEASUREMENT

2

III. Precision of Measuring Volumes
Effect of Eye-Level on Accuracy of Reading Volumes

Meniscus
At Eye-Level

Meniscus
Above Eye-Level

Meniscus
Below Eye-Level

Volume of
Water

Assuming that the volume measured at eye-level is the correct value (7.00 mL), calculate the
error in the volumes read above and below eye-level. (Show work.)

Above eye-level:

Below eye-level:

Eye-Level Meniscus Above Eye-Level
Meniscus

Below Eye-Level

Error

Precision of Volume Using Various Apparatus

Type of Apparatus 10-mL grad cylinder 50-mL grad cylinder 50-mL beaker

Volume of Water

Give the number of decimal places you are able to record with each apparatus:
Type of Apparatus 10-mL grad cylinder 50-mL grad cylinder 50-mL beaker

# of decimal places

Experiment 2: MEASUREMENT

3

IV. Mass Measurement

True Value ________________

Calculations
In the space below, show calculations:

Error

Person 1)

Person 2)

% Error

Person 1)

Person 2)

Results Person 1 Person 2

Error

%Error

Images for Expt 2 Data & Results/Part3 – Effect of Eye-Level.zip

10-mL graduated cylinder with water.html

IMG_4049

csfiles/home_dir/CHEM102.93687.201991/IMG_4049

10-mL graduated cylinder with 7.00 mL of water – a.html

IMG_4053

csfiles/home_dir/CHEM102.93687.201991/IMG_4053

10-mL graduated cylinder with water – held above e.html

IMG_4055

csfiles/home_dir/CHEM102.93687.201991/IMG_4055

10-mL graduated cylinder with water – held below e.html

IMG_4056

csfiles/home_dir/CHEM102.93687.201991/IMG_4056

Table of Contents.html

 

Spring 2022 CCBC CHEM102 W01 22608 Lab Chem&Role in Society(B) – Effect of Eye-Level on Accuracy of Reading Volumes
1. 10-mL graduated cylinder with water

2. 10-mL graduated cylinder with 7.00 mL of water – at eye-level

3. 10-mL graduated cylinder with water – held above eye-level

4. 10-mL graduated cylinder with water – held below eye-level

Images for Expt 2 Data & Results/Part3- Precision of Volume.zip

10-mL graduated cylinder with 7.00 mL of water and.html

IMG_4057

csfiles/home_dir/CHEM102.93687.201991/IMG_4057

50-mL graduated cylinder with the water from the 1.html

IMG_4058

csfiles/home_dir/CHEM102.93687.201991/IMG_4058

50-mL graduated cylinder with water from 10-mL gra.html

IMG_4059

csfiles/home_dir/CHEM102.93687.201991/IMG_4059

50-mL beaker with water from the 50-mL graduated c.html

IMG_4061

csfiles/home_dir/CHEM102.93687.201991/IMG_4061

Table of Contents.html

 

Spring 2022 CCBC CHEM102 W01 22608 Lab Chem&Role in Society(B) – Precision of Volume Using Various Apparatus
1. 10-mL graduated cylinder with 7.00 mL of water and 50-mL graduated cylinder

2. 50-mL graduated cylinder with the water from the 10-mL graduated cylinder

3. 50-mL graduated cylinder with water from 10-mL graduated cylinder and a 50-mL beaker

4. 50-mL beaker with water from the 50-mL graduated cylinder

Images for Expt 2 Data & Results/Part4.zip

Plastic cup 100-g standard weight container of alu.html

IMG_4062

csfiles/home_dir/CHEM102.93687.201991/IMG_4062

Person 1.html

IMG_4063

csfiles/home_dir/CHEM102.93687.201991/IMG_4063

Person 2.html

IMG_4064

csfiles/home_dir/CHEM102.93687.201991/IMG_4064

Table of Contents.html

 

Spring 2022 CCBC CHEM102 W01 22608 Lab Chem&Role in Society(B) – Part 4
1. Plastic cup, 100-g standard weight, container of aluminum metal shots

2. Person 1

3. Person 2

Images for Expt 2 Data & Results/PartI.zip

Rod A with ruler.html

IMG_4065

csfiles/home_dir/CHEM102.93687.201991/IMG_4065

Table of Contents.html

 

Spring 2022 CCBC CHEM102 W01 22608 Lab Chem&Role in Society(B) – Part 1
1. Rod A with ruler

Images for Expt 2 Data & Results/PartII-Measuring with a volumetric flask.zip

100-mL volumetric flask(2).html

IMG_3997

csfiles/home_dir/CHEM102.93687.201991/IMG_3997(1)

100-mL graduated cylinder with water.html

IMG_4042

csfiles/home_dir/CHEM102.93687.201991/IMG_4042

100-mL volumetric flask with funnel and 100-mL gra.html

IMG_4045

csfiles/home_dir/CHEM102.93687.201991/IMG_4045

100-mL volumetric flask with water from 100-mL gra.html

IMG_4046

csfiles/home_dir/CHEM102.93687.201991/IMG_4046

Table of Contents.html

 

Spring 2022 CCBC CHEM102 W01 22608 Lab Chem&Role in Society(B) – Measuring with a volumetric flask
1. 100-mL volumetric flask

2. 100-mL graduated cylinder with water

3. 100-mL volumetric flask with funnel and 100-mL graduated cylinder with water

4. 100-mL volumetric flask with water from 100-mL graduated cylinder

Images for Expt 2 Data & Results/PartII-Measuring with beaker.zip

50-mL beaker with water.html

IMG_4007

csfiles/home_dir/CHEM102.93687.201991/IMG_4007

50-mL graduated cylinder with the water from the 5.html

IMG_4008

IMG_4008

csfiles/home_dir/CHEM102.93687.201991/IMG_4008

csfiles/home_dir/CHEM102.93687.201991/IMG_4008(1)

Table of Contents.html

 

Spring 2022 CCBC CHEM102 W01 22608 Lab Chem&Role in Society(B) – Measuring with a beaker
1. 50-mL beaker with water

2. 50-mL graduated cylinder with the water from the 50-mL beaker

Images for Expt 2 Data & Results/PartII-Measuring with buret.zip

50-mL buret filled with water.html

IMG_4010

Caution: Note that the buret markings run in the opposite direction of the graduated cylinders and beakers.  The zero is at the top and the 50 is at the bottom.  Make your volume readings accordingly.

csfiles/home_dir/CHEM102.93687.201991/IMG_4010

Initial Buret Reading 50-mL buret with water drain.html

IMG_4012

csfiles/home_dir/CHEM102.93687.201991/IMG_4012

50-mL buret with 50-mL graduated cylinder under th.html

IMG_4014

csfiles/home_dir/CHEM102.93687.201991/IMG_4014

Final Buret Reading 50-mL buret with water drained.html

IMG_4015

csfiles/home_dir/CHEM102.93687.201991/IMG_4015

50-mL graduated cylinder with the water drained fr.html

IMG_4016

csfiles/home_dir/CHEM102.93687.201991/IMG_4016

Table of Contents.html

 

Spring 2022 CCBC CHEM102 W01 22608 Lab Chem&Role in Society(B) – Measuring with a buret
1. 50-mL buret filled with water

2. Initial Buret Reading: 50-mL buret with water drained to 1-mL mark

3. 50-mL buret with 50-mL graduated cylinder under the tip

4. Final Buret Reading: 50-mL buret with water drained to 26-mL mark

5. 50-mL graduated cylinder with the water drained from the buret

Images for Expt 2 Data & Results/PartII-Measuring with pipet.zip

25-mL pipet and 50-mL beaker with water.html

IMG_4035

IMG_4035

csfiles/home_dir/CHEM102.93687.201991/IMG_4035

csfiles/home_dir/CHEM102.93687.201991/IMG_4035(1)

25-mL pipet with water from the 50-mL beaker.html

IMG_4036

csfiles/home_dir/CHEM102.93687.201991/IMG_4036

50-mL graduated cylinder with water from the 25-mL.html

IMG_4037

csfiles/home_dir/CHEM102.93687.201991/IMG_4037

50-mL graduated cylinder with water from the pipet.html

IMG_4038

csfiles/home_dir/CHEM102.93687.201991/IMG_4038

Table of Contents.html

 

Spring 2022 CCBC CHEM102 W01 22608 Lab Chem&Role in Society(B) – Measuring with a pipet
1. 25-mL pipet and 50-mL beaker with water

2. 25-mL pipet with water from the 50-mL beaker

3. 50-mL graduated cylinder with water from the 25-mL pipet

4. 50-mL graduated cylinder with water from the pipet

Images for Expt 2 Data & Results/PartII-VolumeMeasurement.zip

Volume-Reading Card.html

IMG_4006

csfiles/home_dir/CHEM102.93687.201991/IMG_4006

50-mL beaker.html

IMG_3985

csfiles/home_dir/CHEM102.93687.201991/IMG_3985

50-mL beaker(1).html

IMG_3986

csfiles/home_dir/CHEM102.93687.201991/IMG_3986

50-mL buret.html

IMG_3987

IMG_3987

IMG_3987

csfiles/home_dir/CHEM102.93687.201991/IMG_3987(1)

csfiles/home_dir/CHEM102.93687.201991/IMG_3987

csfiles/home_dir/CHEM102.93687.201991/IMG_3987(2)

50-mL buret(1).html

IMG_3988

IMG_3988

csfiles/home_dir/CHEM102.93687.201991/IMG_3988

csfiles/home_dir/CHEM102.93687.201991/IMG_3988(1)

50-mL buret(2).html

IMG_3989

IMG_3989

csfiles/home_dir/CHEM102.93687.201991/IMG_3989

csfiles/home_dir/CHEM102.93687.201991/IMG_3989(1)

100-mL volumetric flask.html

IMG_3995

csfiles/home_dir/CHEM102.93687.201991/IMG_3995

100-mL volumetric flask(1).html

IMG_3997

csfiles/home_dir/CHEM102.93687.201991/IMG_3997

25-mL pipet.html

IMG_3991

csfiles/home_dir/CHEM102.93687.201991/IMG_3991

25-mL pipet(1).html

IMG_3993

csfiles/home_dir/CHEM102.93687.201991/IMG_3993

50-mL graduated cylinder.html

IMG_3998

csfiles/home_dir/CHEM102.93687.201991/IMG_3998

50-mL graduated cylinder(1).html

IMG_3999

csfiles/home_dir/CHEM102.93687.201991/IMG_3999

100-mL graduated cylinder.html

IMG_4003

csfiles/home_dir/CHEM102.93687.201991/IMG_4003

100-mL graduated cylinder(1).html

IMG_4004

csfiles/home_dir/CHEM102.93687.201991/IMG_4004

Table of Contents.html

 

Spring 2022 CCBC CHEM102 W01 22608 Lab Chem&Role in Society(B) – Volume Measurement
1. Volume-Reading Card

2. 50-mL beaker

3. 50-mL beaker

4. 50-mL buret

5. 50-mL buret

6. 50-mL buret

7. 100-mL volumetric flask

8. 100-mL volumetric flask

9. 25-mL pipet

10. 25-mL pipet

11. 50-mL graduated cylinder

12. 50-mL graduated cylinder

13. 100-mL graduated cylinder

14. 100-mL graduated cylinder