Data and Results page (Use images to fill in the data)? 2. M2 post lab assignment Material for study is attached. Check link: ht
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
Appendix 1 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
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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
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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
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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
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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
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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
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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
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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
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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
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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 u
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