See the instructions before starting 1. Task1: Complete the data sheet 2. Task2: make the formal lab report Due on 18th March No

Appendix 5 ENTERING SUBSCRIPTS & SUPERSCRIPTS

A-21

In chemistry documents you will often need to include the formula of chemicals that requires the use of subscripts and superscripts. For example, entering “MgSO4” is totally unacceptable as it should be “MgSO4.” Your instructor may allow you to hand write in the subscript “4” but you will probably need to write it in numerous times within the same document and you will likely miss some of them. It is highly recommended that you learn to enter subscripts and superscripts directly on the computer. PROCEDURE FOR WORD 2007 & 2010: The following procedure is specifically for Word 2007 and 2010. The procedure for older versions of Word is on the next page. To enter a number as a subscript, click on the Home tab at the top left corner, and the x2 in the Font area. The superscript mode is accessed in a similar manner.

As an example, follow these steps to enter MgSO4: 1. Type “MgSO” and click on the Home tab at the top left corner, and the x2 in the Font

area. 2. Type “4”, and click on x2 again. This toggles your keyboard back to standard mode. As an example, follow these steps to enter “SO42−” 1. Type “SO” and click on the Home tab, and on x2, then type “4.” 2. Click on x2, type “2-” and then on x2 to toggle back to the standard mode. Alternatively you can use the keyboard shortcut: Ctrl and = (both keys together) put you in the subscript mode. Ctrl, Shift and = (all three keys together) put you in the superscript mode. Pressing this combination of keys will toggle you back to the regular mode. Now test yourself: Open a Word 2007 or 2010 blank document and try typing the following with the subscripts and superscripts properly placed: H2CO3 and CO32−

Appendix 5: ENTERING SUBSCRIPTS & SUPERSCRIPTS

A-22

PROCEDURE FOR WORD 97-2003 First check to see whether the icons for x2 and x2 icons are on your toolbar at the top. A previous user may already have placed them there. If not, follow these directions to place them on your toolbar. TO PLACE THE x2 AND x2 ICONS ON YOUR TOOLBAR: 1. Click on Tools and then on Customize. 2. At the top you will see three tabs: Toolbars, Commands, and Options. Select

Commands. 3. You should now see two lists: Categories and Commands. In the Categories list (on

the left), select Format. 4. In the Commands list (on the right), scroll down until you find x2 Subscript and drag it

up to your toolbar. If you are using your own personal computer (as opposed to a public computer), this icon should remain on your toolbar from now on.

5. In the Commands list, find x2 Superscript and drag it up to your toolbar. TO USE THE x2 AND x2 ICONS THAT YOU PLACED ON YOUR TOOLBAR: To enter a number as a subscript, click on the x2 icon, type the number, then click on the x2 icon again to toggle it back to the standard mode. The superscript mode is accessed in a similar manner. ALTERNATIVELY YOU CAN USE THE KEYBOARD SHORTCUT: Ctrl and = (both keys together) put you in the subscript mode. Ctrl, Shift and = (all three keys together) put you in the superscript mode. Pressing this combination of keys will toggle you back to the regular mode. As an example, to enter MgSO4:

Type “MgSO”, click on x2, type “4”, then click on x2 again. Or use keyboard shortcut:

Type “MgSO”, press Ctrl and = together, type “4”, press Ctrl and = again to toggle back.

As an example, to enter SO42- : Type “SO”, click on x2, type “4”, click on x2, type “2-”, then click on x2 again.

Or use keyboard shortcut: Type “SO”, press Ctrl and = together, type “4”. Press Ctrl, Shift and = all three keys together, type “2-”. Press Ctrl and Shift and = again to toggle back.

Now test yourself: Try typing the following with the subscripts and superscripts properly placed: H2CO3 and CO32−

Experiment 7 ANALYSIS OF PERCENT WATER IN

POPCORN

1

Data Collection and Results Pages Name: __________________________ Date: ___________________

Brand of Popcorn Orville Redenbacher Brand X # of Kernels Used

Mass of Empty Evaporating Dish

Mass of Evaporating Dish + Kernels Before Heating

Mass of Kernels Before Heating

Mass of Evaporating Dish

+ Kernels After Heating

Mass of Kernels After Heating

Mass of Water Lost from Kernels

# of Duds

% Duds

% Water

Experiment 7: ANALYSIS FOR PERCENT WATER IN POPCORN

2

Show the calculations for Orville Redenbacher popcorn. % water ____________________________ % dud ____________________________ Show the calculations for Brand X popcorn. % water ____________________________ % dud ____________________________

Appendix 4 WRITING EXERCISES

A-17

Keep in mind the following points in writing a document in science: • Be clear. • Be complete. • Be concise.

This means that you should know exactly what you want to say and do so in as few words as possible, and yet be clear and complete. This is easier said than done and it takes practice. For this reason, in addition to the above three points, here is one further point which is not limited to science:

Treat your final document as a first draft and take time to proofread and revise for better sentence structure and organization of thought, as well as for correctness in spelling and grammar.

Part I: Writing in the Passive Voice In writing a scientific document, such as a lab report, we tend to write much more in passive voice than in active voice, the reason being that generally who is doing the work, or who is making the observations is not important. Especially when describing a procedure or method, it should be one that anyone skilled in the discipline should be able to do it and get similar results. Thus, we do not want to say, “I did this, and I did that.” Instead, we say, “This was done, and that was done.” Examples:

AVOID THE ACTIVE VOICE IT’S BETTER TO USE THE PASSIVE VOICE

1. I added 40.0 mL of HCl solution to the Mg strip.

2. I saw bubbles forming.

1. To the Mg strip was added 40.0 mL of HCl solution.

2. Formation of bubbles was observed.

Practice Exercise 1 Rewrite the following sentences in passive voice. 1. I transferred the contents of the beaker to the graduated cylinder. 2. I found the slope of my graph is 0.04 g/min. 3. I added 3 drops of bromophenol indicator to the Erlenmeyer flask. Part II: When the Passive Voice is Not Necessary Note that we are not saying passive voice is always necessary. It is generally used when the doer is unknown or unimportant, as discussed in Part I. It is used occasionally to change the tone for variety. As a rule of thumb, if the first person singular pronoun is not involved, the active voice is preferred because it is less wordy, more direct and at times, less awkward. Using the pronoun “we” is acceptable when “we” refers to an inclusive “I” and the readers. This is a way to indicate that not just the writer but everyone reading the document is considered. If necessary, use “one” instead of “I” or “you.” See examples that follow.

Appendix 4: WRITING EXERCISES

A-18

Examples of acceptable use of “we” or “one”:

1. From the color of the endpoint we can conclude that the equivalent point has been reached.

2. From the color of the endpoint one can conclude that the equivalent point has been

reached. 3. We can conclude definitively that chloride ions are present in the unknown. 4. One can conclude definitively that chloride ions are present in the unknown.

Part III: Writing Experimental Procedures or OR Methods

When writing a lab report, the experiment has already been performed. The “experimental methods” or “experimental procedure” is meant to describe what you had ALREADY done. You are not writing a lab manual to tell others what they have to do, or what you are about to do. Thus, past tense rather than present tense is to be used, in addition to writing in passive voice.

Example:

INCORRECT PREFER PAST TENSE, PASSIVE VOICE

1. Weigh and record the flask containing the residue.

2. I heated the yarn in a clean test tube.

1. The flask containing the residue was weighed and the mass recorded.

2. The yarn was heated in a clean test tube. Practice Exercise 2 Rewrite the following sentences in the preferred tense and voice (past tense, passive voice). 1. Cover the calorimeter with the cardboard lid and insert a second temperature probe

through one of the holes in the lid. 2. Stir the mixture thoroughly with a clean spoonula and grind any lumps that you may find

into fine grains. 3. Examine the popped corn and record the number of duds.

Appendix 4: WRITING EXERCISES

A-19

Part IV: Writing the Experimental Method in an Abstract In an abstract, the “experimental method” must not include details of size of equipment and quantities of samples used unless this information is critical to the method (which usually is not the case). What is to be included in an abstract should not be the “procedure” but just a “method” used. See example that follows in the difference between “procedure” and “method.” Example of a Procedure:

1. Record the unknown number. 2. Place the unknown metal on the balance pan and record the mass. 3. Next place exactly 5.00 mL of water in a 10-mL graduated cylinder. Then slowly

slide the unknown metal into the graduated cylinder, taking care not to let any water splash out. Record the total volume to 2 decimal places.

4. Calculate the volume of the metal by subtracting 5.00 mL from the total volume. Calculate the density of the metal by dividing the mass of the metal by the volume of the metal.

Example of an Experimental Method (as in an abstract): The volume of the unknown metal was determined by its displacement of water and the mass was determined on a balance. From the volume and mass thus obtained, the density of the metal was calculated.

Practice Exercise 3 Write the experiment method for an abstract from the procedure described below:

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.

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

3. Repeat with the cylinder at eye-level and below eye-level. 4. Complete the calculations specified on the Data and Results section.

Appendix 4: WRITING EXERCISES

A-20

SAMPLE OF A FORMAL LAB REPORT

15

A formal chemistry lab report generally contains specific sections: title of the report,

abstract, introduction, experimental section, results and discussion, conclusions, and

references.

Title The title tells exactly what the experiment or report is about. The title is centered. The

name (s) of the student(s), address of the institution, and date come after the title. If more

than one name is on the report, an asterisk is placed by the name of the author.

Abstract: This section is a one-paragraph summary in about 100 to 200 words, usually in

boldface and single spaced. It includes the purpose and importance of the experiment or

study, the experimental method, the major results, and the conclusions drawn. Specific

information about the experiment or study must be written in the past tense. The present

tense is only used for accepted facts—concepts and principles. Please note that although

this portion of the report comes right after the title, it is the section that is written last

because it is a summary of the report.

Introduction This section provides background information (theory and previous research). It states the

goals/objectives and provides a short description of the experimental design. The past

tense is used except for well-established facts. A separate paragraph is used for each major

point. Sources used must be properly cited. Generally, in-text citations are indicated either

as numeric superscripts, italicized numbers in parentheses, or author surname-year in

parentheses.

Experimental Section

This section usually comes after the “Introduction” section in scientific journals and is in

two parts: Methods and Materials and Procedure. The first part outlines the methods

and materials used. Well-known methods and materials are generally referenced rather

than written out. The “Procedure” follows the materials and methods. (For your report,

you will write procedure only.) Complete sentences in the past tense and passive voice are

used in this section. Subject pronouns such as “I” or “we” should be avoided. The steps in

an experiment are not numbered. If an experiment involves two or more different

activities, each activity must be clearly identified with subheadings.

Results and Discussion This section comes after the procedure in the "Experimental Section." This section gives

the data and results and a discussion of the results. The major focus in this section is on

calculations, tables, graphs, errors, and deviations. Here we compare the results obtained

from the experiment with the expected results. If the results are what you expected,

indicate which theory or law they are consistent with. If results are inconsistent with

expected results, account for the errors. The past tense is used to discuss the experimental

findings and present tense is used for accepted facts and scientific principles.

SAMPLE FORMAL LAB REPORT

16

Conclusions This section comes after the “Results and Discussion” section. It states what you discover

after performing the experiment.

References In this section, the sources cited in the rest of the writing are listed. Note that “references”

is different from “bibliography.” “References” is a list of sources of information you had

cited in the lab report. “Bibliography” is a list of sources of information from which you

obtained general knowledge of a particular topic without directly quoting from it.

In some journals, references are placed at the end of the article; in others, they are indicated

as footnotes. Journals published by the American Chemical Society (ACS) utilize two

methods of citing references: by superscript numbers, or by italic numbers in parentheses.

Your instructor may specify which method you should use. If none is specified, you may

select one method and use it consistently for the entire report.

For example, in the body of the text, the literature value is assigned a “reference number”

as shown:

The BP is given as 67°C in the literature.1

The BP is given as 67°C in the literature (1).

At the end of the report, all the reference sources are listed in numerical order. Having

the list of references at the end of the report is the easier method than to have them as

footnotes. Below are examples of how references are to be listed according to the ACS

Style guide.

UNPUBLISHED DATA (such as data from fellow classmates):

Smith, J. CCBC-Catonsville, personal communication, Feb 2015.

BOOK:

Author’s last name, initials, Title (in italics), edition; Publisher: City, State (in 2

letters), Year; Pages or Chapter.

Malone, L. J. Basic Concepts of Chemistry, 7th ed.; John Wiley & Sons: St.

Louis, MO, 2004, pp 145-148.

HANDBOOK:

CRC Handbook of Chemistry and Physics, 81st ed. Lide, D.R., Ed.; CRC

Press: Boca Raton, FL, 2000-2001; p. 4-73.

JOURNAL:

Author’s last name, initials (separated by semicolon if more than one). Title of

Journal (italics). Year (bold), Volume (italics), Page.

Liu, S.; Armes, S. P. J. Am. Chem. Soc. 2001, 123, 9910.

SAMPLE FORMAL LAB REPORT

17

A Sample Formal Report

Determination of the Concentration of an Aqueous

Solution of HCl

Jane Smith and John Doeber*

The Community College of Baltimore County

7201 Rossville Blvd, Baltimore, MD 21237-3899

June 9, 2015

Abstract: The purpose of the experiment was to determine the concentration of an aqueous solution of HCl (Unknown #159). A solution of NaOH of known

concentration (0.1000 M) was used to titrate against the solution of HCl with

phenolphthalein as the indicator. Three trials were performed and the average

concentration of the HCl solution was found to be 0.1475 M with an average

deviation of 0.07%, and an error of 2.9%.

Introduction Titration1 is a technique that can be used to determine the concentration of a solution by

carefully reacting it with another solution of known concentration. In this experiment, the

titration method is used to determine the concentration of an HCl solution. This was done by

titrating a sample of the solution against a solution of NaOH of known concentration. The

reaction involved is as follows:

HCl (aq) + NaOH (aq)  H2O (l) + NaCl (aq)

Phenolphthalein was used as the indicator which changes from colorless when acidic to pink

when basic. With the HCl solution in the flask, the solution would be colorless initially. When

just enough of the NaOH solution has been added to neutralize the HCl solution, the solution

would change to a pale pink.2 By measuring how much of the NaOH solution is needed to

neutralize the HCl solution, the concentration can be determined.

Experimental Section

A solution of HCl labeled as Unknown #159 was used in the experiment. Four 250-mL

Erlenmeyer flasks were labeled 1 through 4. Into each flask was added 25.00 mL of the HCl

solution, 50.0 mL of deionized water, two drops of phenolphthalein, and a magnetic stir bar.

A 50-mL buret was set up on a ring stand and filled with 0.1000 M NaOH. A magnetic stir

plate was set up under the buret. Flask 1 (serving as a rough trial) was placed on the stir plate

under the buret and titrated with the 0.1000 M NaOH until a faint pink color developed and

remained for 30 seconds. The volume of NaOH used in the rough trial was noted in order to

serve as a guide to obtaining a good endpoint for the other three trials. For each of the other

SAMPLE FORMAL LAB REPORT

18

three flasks, the NaOH was run in quickly until the volume added was about 1 mL less than

the volume used in the rough trial. Then for each flask, the NaOH was added drop-wise until

a faint pink color persisted for 30 seconds. The volume of NaOH used for each flask was

carefully noted and used to calculate the concentration of the HCl solution. The average

concentration (or mean), the deviation, and average deviation were also calculated. The true

value for the concentration of the HCl was provided and this value was used in the calculation

of the percent error.

Results and Discussion

The volume of 0.1000 M NaOH used for Trials 2, 3, and 4 were 35.28 mL, 35.20 mL, and

35.26 mL, respectively. The data and concentration results are summarized in the table

below.

Table: Data and Results for the Titration of HCl (#159) with 0.1000 M NaOH

Trial Rough # 2 #3 #4

Final Buret Reading (mL) 36.90 35.38 36.26 35.81

Initial Buret Reading (mL) 1.12 0.10 1.06 0.55

Volume of NaOH Dispensed (mL) 35.78 35.28 35.20 35.26

Concentration of HCl (M) 0.1411 0.1408 01.410

Deviation of Concentration (M) 0.0001 0.0002 0.0000

The range in the volume of NaOH used in the three good trials was 0.08 mL. For titrations

where the same amount of titrate is used, a range of less than 0.1 mL is indicative of good

precision.3

According to the balanced equation for the reaction, HCl and NaOH react in a 1:1 ratio.

HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

Therefore, using the volume of NaOH reacted in each trial and the molarity of NaOH, the

molarity of HCl (Unknown #159) was calculated. The calculation of the HCl concentration

for Trial 2 is shown below.

35.28 mL NaOH( 1 𝐿

1000 𝑚𝐿 ) (

0.1000 𝑚𝑜𝑙 𝑁𝑎𝑂𝐻

1 𝐿 ) (

1

0.02500 𝐿 ) = 0.1411 𝑀

The concentrations calculated for Trial 3 and Trial 4 are done in a similar manner. The

average (or mean) concentration of HCl was found to be 0.1410 M. The deviation from the

mean for Trials 2, 3, and 4 are 0.0001 M, 0.0002 M, and 0.0000 M, respectively. The

calculation of the deviation from the mean for the concentration of HCl is calculated as

shown below for Trial 2.

Deviation from Mean = |experimental value  average value|

= |0.1411  0.1410| M = 0.0001 M

SAMPLE FORMAL LAB REPORT

19

The deviations in the concentrations for Trial 3 and Trial 4 are calculated in a similar manner.

The average deviation was found to be 0.0001 M, indicating that the result was very precise.

This is supported by the relative mean deviation (RMD) which is calculated to be 0.7 parts

per thousand. The calculation of the RMD is shown below.

Relative Average Deviation = 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑑𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛

𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 x 1000

= 0.0001 𝑀

0.1410 𝑀 x 1000 = 0.7 𝑝𝑝𝑡

An RMD of less than 1 part per thousand indicates good precision. And, although precision

and accuracy are not the same, good precision suggests good accuracy.

The only way to know the accuracy of the result is if the true value is known. If the true value

for the concentration of the HCl solution (Unknown #159) was 0.1452 M, the percent error in

the determination of the HCl concentration would be -2.9%. The percent error is calculated as

follows:

% error = 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑣𝑎𝑙𝑢𝑒−𝑡𝑟𝑢𝑒 𝑣𝑎𝑙𝑢𝑒

𝑡𝑟𝑢𝑒 𝑣𝑎𝑙𝑢𝑒 x 100

= 0.1410 𝑀−0.1452 𝑀

0.1452 𝑀 x 100 = −2.9%

The error calculation shows that the concentration of the HCl was less than the expected value.

The percent error of 2.9% shows that the accuracy was good, but could be improved upon.

The negative sign tells us that reported molarity is lower than the correct value. Perhaps the

error was due to the pipet used to deliver the HCl solution. It might not have been properly

calibrated. This would explain why the precision was excellent and yet the accuracy was not

as good as expected.

Conclusions The concentration of Unknown # 159 was determined to be 0.1411 M HCl, based on three

titration trials, with a relative average deviation of 0.7 parts per thousand and an error of

2.9%. The closeness of the experimental value (0.1411 M) to the true value (0.1452 M))

suggests that a simple acid-base titration is an effective method for finding the concentration

of an acid.

References 1. Yau, C. L. Chem 108 Experiments in Fundamentals of Chemistry Laboratory, 2nd Ed;

Academx: Baltimore, MD, 2007; pp 135-139.

2. Yau, C. CCBC-Catonsville, personal communication, 2015. 3. Poppins, M. J. Chem. Educ. 2017, 96, 23-29.

SAMPLE FORMAL LAB REPORT

20

Experiment 7 ANALYSIS FOR PERCENT WATER IN

POPCORN

1

Purpose: To investigate the percentage by mass of water in commercial popcorn and see if the popping ability is affected by the percentage of water in the kernels before popping. Introduction A kernel of popcorn has three main regions as shown in Figure 7.1: the germ (which is the reproductive part), the pericarp, and the endosperm. The pericarp is a tough shell that can withstand pressures of up to 9 atmospheres. The endosperm is made up of two kinds of starch: hard or translucent starch and soft or opaque starch. Commercial popcorn kernels contain about 13-15% by mass of water for optimum popping ability. When popcorn is heated sufficiently, the water within the kernels is converted to water vapor, which expands with increasing temperature until it bursts out of the pericarp. In the process, the hard or translucent starchy material of the corn fluffs up and becomes “popped” corn. Figure 7.1

Sometimes there is a crack in the pericarp of the kernels allowing the water vapor to slowly leak out. In such a case, no pressure will build up to “pop” the shell, and we have a “dud.” A stale kernel that has lost its water will also not be able to pop and end up as a “dud” as well.

In this experiment you will determine the percentage of water in two brands of popcorn by weighing them before and after they have been popped and the percent duds in each sample. The percent by mass of water is determined as follows:

% water = !"## !" !"#$% !"#$ !"#$ !"#$"%&

!"## !" !"#$"%& !"#$%" !"!!#$ x 100

The percent duds can be determined as follows:

% duds = !"#$%& !" !"#$##%& !"#$"%& (!"!#)

!"#$%& !" !"#$"%& !"#$ x 100

Equipment/Materials Electronic balance, ceramic heat pad, crucible tongs, iron ring, ring stand, wire gauze, lab burner, evaporating dish, 250-mL beaker, 100-mL beakers (2), watch glass, aluminum foil, Orville Redenbacher popcorn (unpopped), unknown Brand X popcorn (unpopped). Warning: Materials provided in the lab are for experiments only. Never consume any of the materials provided for experiments.

Experiment 7: ANALYSIS FOR PERCENT WATER IN POPCORN

2

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

1. Obtain a ceramic heat pad and a pair of crucible tongs. Attach an iron ring onto a ring stand, place a wire gauze on top, and place a lab burner below the ring. Position the iron ring at a height such that the tip of the blue cone of the flame would be touching the wire gauze. Adjust as necessary.

2. Heat the wire gauze (without the beaker) for 5 minutes to drive off any moisture that may have collected on it. Turn off the burner after 5 minutes.

3. Weigh and record the mass of a clean and dry evaporating dish. Place exactly 10

kernels of Orville Redenbacher popcorn in the evaporating dish and record the total mass of the dish and kernels. (From the two masses the mass of the kernels can be calculated. This is called weighing by difference. In other words, you are not measuring the mass of the kernels directly, but determining the mass by weighing the dish before and after the kernels have been added.)

4. Obtain a 250-mL beaker and remove any labels that may have been left on it. (They

will char and burn if you don’t!) Wrap the sides (not the bottom) of the 250-mL beaker with aluminum foil to provide insulation (see demonstration setup). Place the evaporating dish on top of the beaker, cover it with a watch glass, and set everything on top of the wire gauze a

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