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## Accuracy And Precision Chemistry Homework Help Case Assignment

Order ID53563633773 TypeEssay Writer LevelMasters StyleAPA Sources/References4 Perfect Number of Pages to Order5-10 Pages

Description/Paper Instructions

Accuracy And Precision Chemistry Homework Help Case Assignment

Lab 1: Measurement: Accuracy and Precision

Lab Materials:

Rulers

Non-programmable calculator

1 Sheet of notebook paper

Scissors

Stopwatch

Kitchen Balance (measures to nearest 1g)

Plastic cups

Measuring spoons

Water

2

Name: ___________________________ Date: _____________

Measurement: Accuracy and Precision

When scientists collect data, they must determine the accuracy and precision of their measurements.

Accuracy refers to how close the measured quantities are to the actual or true value. Precision refers to

the closeness of each of the data sets to one another. To distinguish between these two terms, it is

useful to think of a target and the position of the measurements on the target. If the measurements are

clustered together but away from the center of the target, then we would say the measurements are

precise, but not accurate. If the data hits the center on the target, the measurements are precise and

very accurate, i.e. the values collected are close to the true value one should obtain. In today’s lab,

you will make measurements and perform calculations to the appropriate number of significant figures.

You will then determine if your measurements are precise and/or accurate. Before doing this though,

you will have several exercises that test your knowledge of significant figures.

Significant Figures

In any given measurement, non-place holding digits are referred to as significant digits or most often

“sig figs” (for significant figures). The greater the number of sig figs, the greater the precision in the

measurement. To determine the number of significant figures in a given quantity, follow these rules:

- All nonzero numbers are significant.
- Zeroes located between two numbers are significant.
- Zeroes located after a decimal point are significant
- Zeroes located to the left of the first nonzero number are NOT significant; therefore, the
number 0.002 has only 1 significant figure since the 3 zeroes prior to the number 2 are

serving only as place holders.

- Zeroes located at the end of a number but before a decimal point are ambiguous. For
instance, we cannot determine the number of sig figs in say, 6350. To avoid this

confusion, we either write 6350. or 6.350 x 103 to indicate that the zero is significant.

- Exact numbers (numbers obtained from counting or numbers originating from defined
quantities, such as 12 inches = 1 foot) have infinite number of significant digits.

- For the following examples, determine the number of significant figures.
- 4762 __________
- 902 __________
- 0.0000438 __________
- 987,000,000,000 __________
- 0.000834 __________
3

- 4.32 x 10 4 __________
- 9.2735 x 10 -5
__________

- 6,049,071 __________
- 678.20 __________
- 903,089,932,000. __________
Significant Figures in Calculations

One important concept to remember when you perform mathematical calculations is that the answer

you report must reflect the precision in the quantities you measured. Your answer should not show

more precision that what you were capable of measuring; therefore, when doing mathematical

calculations, there should not be a gain or loss in precision.

The rules to follow for determining the number of significant figures depends on the type of

mathematical operation you are performing.

Multiplication and Division

The reported answer should carry the same number of significant figures as the quantity with

the fewest number of significant figures.

Addition and Subtraction

The reported answer should carry the same number of decimal places as the quantity with the

fewest decimal places.

When performing these calculations, it will most likely be necessary to round your final answer to the

appropriate number of significant figures. To round your answer, look for the left-most digit being

dropped. If this digit is four or less, round your answer down; however, if this digit is 5 or greater,

round your answer up.

**Important Note** For calculations involving both multiplication/division and addition/subtraction,

do NOT round your answer in intermediate steps. Determine the number of significant figures in each

step, but use the entire answer from each step in later steps. ALWAYS round your FINAL answer,

NOT the intermediate answers.

- For each of the following, report your answer to the correct number of significant figures.
- 20.76 x 4.89 x 1.2 __________
- 15.67 – 0.789 + 9.5 __________
- (3,789 – 2,569)/2.5 __________
4

- 7.94 – 3.25 x 2 __________
- 3,789 – 2,569/2.5 __________
Measurements

- Below are data sets from three students who were measuring the length of a piece of string.
Student A: Student B: Student C:

8.2 cm 5.2 cm 6.1 cm

8.4 cm 3.4 cm 5.9 cm

7.9 cm 7.2 cm 6.2 cm

- The true length of the string is 6.2 cm. Which student(s) measurements is/are accurate?
- Which student(s) measurements is/are precise?
- Are any of the students’ measurements both precise and accurate? Please explain.
- Length
1

- Fold a piece of notebook paper into eight uniform rectangles, and then cut them out. Take one
of the rectangles and using a best guess, try drawing a 6.5 cm line on it without using any

measuring device. Set this paper aside. Without looking at this piece of paper, try drawing

another 6.5 cm line on 3 more rectangles. Now, using a ruler, measure the exact length of each

of your lines to the appropriate number of sig figs, and record them in the table below.

Measured Length, cm

Trial 1 Trial 2 Trial 3 Trial 4

5

- Calculate the average of your results. To receive credit, you must show your work.
- What is your percent error? Show your work.
- Comment on the accuracy and precision of your measurements.
- On the remaining 4 rectangular pieces, try again to draw a 6.5 cm line on each of them. Again,
do not use any measuring device when drawing the lines and do not refer to previous drawings.

When you have finished, again measure the actual length of the lines and record your results in

the table below.

- What is the average and percent error of your measurements? Again, work must be shown to receive credit.
Measured Length, cm

Trial 1 Trial 2 Trial 3 Trial 4

6

- How do your results compare to your first set of measurements? Which set is more accurate? More precise? Please explain.
- Time
1

- Using a stopwatch, close your eyes, and try to estimate the passing of 30 seconds. Record the
actual time that has passed in the table below. Repeat this 3 more times.

- What is the average and percent error of your measurements?
- Did your accuracy improve with subsequent trials?
- Surface Area
Choose any regular shaped object (your desk, a table, your textbook) and calculate the surface area

in cm 2 . Record each individual measurement below and show a calculation of the surface area.

Make sure your measurements and answers are to the appropriate number of significant figures.

Measured Time, s

Trial 1 Trial 2 Trial 3 Trial 4

7

- Mass
Obtain a plastic cup, kitchen balance, and measuring spoon. When using a balance, please follow

these general guidelines:

- Always make sure the balance reads zero before and after you make a measurement. Use the
“Tare” button to zero the balance before you place the object/chemical on the balance.

- To obtain an accurate measurement, always make sure the item you are measuring is at room
temperature.

- NEVER place any chemical directly on the balance. It should always be in the container
specified in the lab procedure. If none is specified, then a plastic cup can be used.

Record the following measurements. Do NOT empty any of the water out of your cup in between

readings, and only tare the balance prior to obtaining your first measurement in part a below.

- Mass of plastic cup, g ____________
- Mass of 1 tablespoon of water, g ____________
- Mass of 2 nd
tablespoon of water, g ____________

- Mass of 3 rd
tablespoon of water, g ____________

- Average mass of a tablespoon of water, g ____________
(Show work)

- Greatest difference of 3 masses (largest mass – smallest mass) ____________
(Show work)

- Knowing that 1 tablespoon = 14.79 mL (milliliters), what is the density (D) of water at room
temperature? Please note that density is equal to mass/volume and has units of g/mL.

Reference: 1 Author Unknown,

http://www.sciencebyjones.com/PDF%20files/accuracy%20and%20precision%20home%20lab%2020

04%20PDF%203.pdf, accessed Aug. 17, 2009.

Accuracy And Precision Chemistry Homework Help Case Assignment

RUBRIC

QUALITY OF RESPONSENO RESPONSEPOOR / UNSATISFACTORYSATISFACTORYGOODEXCELLENTC ontent (worth a maximum of 50% of the total points)Zero points: Student failed to submit the final paper.20 points out of 50: The essay illustrates poor understanding of the relevant material by failing to address or incorrectly addressing the relevant content; failing to identify or inaccurately explaining/defining key concepts/ideas; ignoring or incorrectly explaining key points/claims and the reasoning behind them; and/or incorrectly or inappropriately using terminology; and elements of the response are lacking.30 points out of 50: The essay illustrates a rudimentary understanding of the relevant material by mentioning but not full explaining the relevant content; identifying some of the key concepts/ideas though failing to fully or accurately explain many of them; using terminology, though sometimes inaccurately or inappropriately; and/or incorporating some key claims/points but failing to explain the reasoning behind them or doing so inaccurately. Elements of the required response may also be lacking.40 points out of 50: The essay illustrates solid understanding of the relevant material by correctly addressing most of the relevant content; identifying and explaining most of the key concepts/ideas; using correct terminology; explaining the reasoning behind most of the key points/claims; and/or where necessary or useful, substantiating some points with accurate examples. The answer is complete.50 points: The essay illustrates exemplary understanding of the relevant material by thoroughly and correctly addressing the relevant content; identifying and explaining all of the key concepts/ideas; using correct terminology explaining the reasoning behind key points/claims and substantiating, as necessary/useful, points with several accurate and illuminating examples. No aspects of the required answer are missing.Use of Sources (worth a maximum of 20% of the total points).Zero points: Student failed to include citations and/or references. Or the student failed to submit a final paper.5 out 20 points: Sources are seldom cited to support statements and/or format of citations are not recognizable as APA 6^{th}Edition format. There are major errors in the formation of the references and citations. And/or there is a major reliance on highly questionable. The Student fails to provide an adequate synthesis of research collected for the paper.10 out 20 points: References to scholarly sources are occasionally given; many statements seem unsubstantiated. Frequent errors in APA 6^{th}Edition format, leaving the reader confused about the source of the information. There are significant errors of the formation in the references and citations. And/or there is a significant use of highly questionable sources.15 out 20 points: Credible Scholarly sources are used effectively support claims and are, for the most part, clear and fairly represented. APA 6^{th}Edition is used with only a few minor errors. There are minor errors in reference and/or citations. And/or there is some use of questionable sources.20 points: Credible scholarly sources are used to give compelling evidence to support claims and are clearly and fairly represented. APA 6^{th}Edition format is used accurately and consistently. The student uses above the maximum required references in the development of the assignment.Grammar (worth maximum of 20% of total points)Zero points: Student failed to submit the final paper.5 points out of 20: The paper does not communicate ideas/points clearly due to inappropriate use of terminology and vague language; thoughts and sentences are disjointed or incomprehensible; organization lacking; and/or numerous grammatical, spelling/punctuation errors10 points out 20: The paper is often unclear and difficult to follow due to some inappropriate terminology and/or vague language; ideas may be fragmented, wandering and/or repetitive; poor organization; and/or some grammatical, spelling, punctuation errors15 points out of 20: The paper is mostly clear as a result of appropriate use of terminology and minimal vagueness; no tangents and no repetition; fairly good organization; almost perfect grammar, spelling, punctuation, and word usage.20 points: The paper is clear, concise, and a pleasure to read as a result of appropriate and precise use of terminology; total coherence of thoughts and presentation and logical organization; and the essay is error free.Structure of the Paper (worth 10% of total points)Zero points: Student failed to submit the final paper.3 points out of 10: Student needs to develop better formatting skills. The paper omits significant structural elements required for and APA 6^{th}edition paper. Formatting of the paper has major flaws. The paper does not conform to APA 6^{th}edition requirements whatsoever.5 points out of 10: Appearance of final paper demonstrates the student’s limited ability to format the paper. There are significant errors in formatting and/or the total omission of major components of an APA 6^{th}edition paper. They can include the omission of the cover page, abstract, and page numbers. Additionally the page has major formatting issues with spacing or paragraph formation. Font size might not conform to size requirements. The student also significantly writes too large or too short of and paper7 points out of 10: Research paper presents an above-average use of formatting skills. The paper has slight errors within the paper. This can include small errors or omissions with the cover page, abstract, page number, and headers. There could be also slight formatting issues with the document spacing or the font Additionally the paper might slightly exceed or undershoot the specific number of required written pages for the assignment.10 points: Student provides a high-caliber, formatted paper. This includes an APA 6^{th}edition cover page, abstract, page number, headers and is double spaced in 12’ Times Roman Font. Additionally, the paper conforms to the specific number of required written pages and neither goes over or under the specified length of the paper.## GET THIS PROJECT NOW BY CLICKING ON THIS LINK TO PLACE THE ORDER

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