2: LAB 2 - INSTRUMENTAL MEASUREMENTS
- Page ID
- 506120
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The purpose of this experiment is to:
- Record measurements of length, mass, volume, and temperature.
- Measure the mass and volume of an unknown rectangular solid.
- Demonstrate proficiency in using the following instruments: metric rulers, balances, graduated cylinders, and thermometers.
INTRODUCTION
Chemistry, a fundamental branch of science, is an experimental science. It is a qualitative science based on measurements that depends on careful observations of experiments, yielding accurate and precise results through the use of good laboratory techniques and instruments or devices.
In the chemistry laboratory, you must precisely measure length, mass, volume, and temperature for various experiments. To reinforce your understanding of common laboratory concepts and techniques and to gain knowledge in data gathering, this laboratory will explore and master fundamental operations using standard instruments and devices, thereby enhancing your success.
Measurements consist of two parts: a numerical part and a unit (sometimes called a dimension).
Example:
Please make it a habit to always include the unit with each number you use.
Measurements made are not always accurate. The size of the discrepancy depends on several factors, including the skill of the person performing the measurement and the instrument or device used for the measurement. The margin of error in each measurement refers to the uncertainty associated with that measurement. The instrument itself limits how close one can come to a perfect measurement.
The measurements need to be precise and accurate. Exact measurements are those that consistently give close results. Accurate results are those that are close to the actual value. Precise and accurate measurements require instruments that are properly calibrated and functioning correctly. Additionally, the person performing the measurement must be familiar with using the instrument and follow the procedure carefully. By doing repeated measurements, one can estimate the precision of the instrument and the operator.
Measurement of Length
Length measurements in chemistry laboratories are mostly done using rulers in metric units. The rulers (Figure 1) are marked with standard distances in centimeters at the top and inches at the bottom, and the intervals on the ruler are referred to as hash marks.
Measure the length of the yellow rectangle using a ruler
Solution
In measurements, all the figures recorded are significant, including certain digits plus the estimated digit. On Ruler, the yellow rectangle appears to be 12.6 cm long. You can estimate one digit between the scale markings and measure 12.60 cm.
Measurement of Mass
Another common and essential operation in the chemical laboratory is determining the mass of given objects or samples. For that purpose, a suitable balance must be used. In the lab, you will primarily use the milligram or analytical balances in the balance room. The analytical balances weigh the nearest 0.001 gram, and all the digits should be recorded for the exact mass.
Figure 2. Milligram balance
Analytical balances are expensive and delicate, so care should be taken when using them. Always tare the balance, i.e., zero it before measuring the mass. Ensure the object you are measuring is always at room temperature, neither cold nor hot, to obtain an accurate mass measurement.
Many of the experimental procedures in this course require accurate quantitative values. In such instances, an analytical balance will be employed in weight determinations.
Measurement of Volume
Graduated cylinders, pipettes, or burettes are commonly used to measure volume. Volume in the laboratory is generally expressed in milliliters (mL) or cubic centimeters (cm3)
Measure the volume of water in the graduated cylinder in Figure 3.
Figure 3: To measure the volume of liquid in this graduated cylinder.
Solution
The graduated cylinder with water above shows that the bottom of the meniscus lies between the 21 and 22 markings, indicating that the liquid volume is undoubtedly more than 21 mL but less than 22 mL. The meniscus appears closer to the 22-mL mark than the 21-mL mark, so a reasonable estimate of the liquid’s volume would be 21.6 mL. In the number 21.6, the digits 2 and 1 are specific, but the 6 is an estimate.dd example text here.
Calculate the volume of a regular rectangular solid whose length, width, and height are measured to be 12.00 cm, 4.00 cm, and 5.00 cm, respectively.
Solution
Volume of a rectangular solid is = L x W x h = 12.00 cm x 4.00 cm x 5.00 cm = 240.00 cm3
Measurement of Temperature
In chemistry laboratories, temperature measurement is performed using thermometers that contain colored liquid or are digital, typically in degrees Celsius. Other temperature scales that may be used are Fahrenheit and Kelvin.
Formulas for converting one temperature scale to another:
K = C + 273.15 °C = 
°F = (°C * 1.8) + 32.
Figure 4: A Comparison of Fahrenheit (°F), Celsius(°C), and Kelvin (K) Temperature Scales showing the difference between the freezing point of water and the boiling point of water.
A student measures the temperature of boiling water to 99.5 °C. What would boiling water temperature be in degrees Fahrenheit (°C) and Kelvin?
Solution
°F = (°C * 1.8) + 32 = (99.5 °C x 1.8) + 32 = 211.1 °F
K = C + 273.15 = 99.5 °C + 273.15 = 372.75 K
EQUIPMENT* AND CHEMICALS NEEDED
| Equipment | Equipment |
|---|---|
| Safety goggles | Large Test tube |
| Ruler - Centimeter and Inches | 10.0 mL and 100.0 mL graduated cylinders. |
| Watch glass. | 100.0 mL Beaker |
| Index card | Unknown Rectangular block |
| Milligram balance | Celsius Thermometer |
| Deionized water |
* Images of equipment needed in this lab can be found in the appendix (the equipment may differ or be subject to changes; follow your instructor’s directions).
- Always wear chemical splash goggles during the experiment.
- Gloves are provided for those who wish to wear them.
- Exercise extreme caution when using a hot plate or Bunsen burner to heat water.
- Discard used water down the drain.
- Ensure all glassware is clean and all equipment is returned to its designated place.
- Clean the lab benches and verify all equipment is in your lab drawer before leaving.
- Wash your hands as soon as you leave the lab.
EXPERIMENTAL PROCEDURE
A. Measurements of Length
1. Using the ruler, measure the length and width of the index card provided to your group in both inches and centimeters.
2. Measure the length of the 10.0 mL graduated cylinder in your lab drawer.
3. Measure the diameter of the watch glass in your lab drawer and compare it to that of other groups in your lab.
B. Measurements of Mass.
4. Using an analytical balance, measure the mass of the evaporating dish in your lab drawer.
5. Measure the mass of a watch glass in your lab drawer and compare it to that of other groups in your lab.
6. Measure the mass of a large test tube and compare it to that of other groups.
C. Measurements of Volume.
7. Take a 100.0 mL beaker, fill it with water to a volume of 50.0 mL, and pour it into a 100.0 mL graduated cylinder. Record the exact volume.
8. Fill the large test tube with water and record the exact volume by pouring it into the graduated cylinder.
D. Measurement of Mass and Volume of Unknown Solid.
9. Note the unknown rectangular solid color and the unknown number or letter.
10. Measure and record the exact mass of the solid using an analytical balance.
11. Using a ruler, measure and record its length, width, and height in cm.
12. Calculate the volume of the solid
E. Measurements of Temperature
14. Obtain a degree Celsius (°C ) thermometer.
15. Measure the room temperature and record the result.
16. Measure and record the temperature of cold tap water.
17. Measure and record the temperature of hot tap water (to hot/warm water provided by the instructor).
PRE-LAB QUESTIONS
Name: ______________________________
- In a chemistry laboratory, metric units are used for various measurements. Give the most commonly used metric unit for the measurements listed below:
a) Mass:
b) Length:
c) Temperature:
d) Volume
- What are the SI units for the following measurements?
a) Mass:
b) Length:
c) Temperature:
d) Volume:
- Normal human body temperature is 98.6 degrees Fahrenheit (°F). Convert it to corresponding degrees Celsius (°C) and Kelvin temperatures. (Show your work.)
DATA AND OBSERVATIONS
Name: _________________________Lab Partner(s): ______________________________
A. Measurements of Length.
|
|
|
Centimeters |
Inches |
|---|---|---|---|
|
1a. |
Length of an Index card |
||
|
1b. |
Width of an Index card |
||
|
2. |
Length of the 10 mL graduated cylinder |
||
|
3. |
Diameter of the watch glass |
4. Compare your measurements with those of another group in the lab. How do they compare and explain?
B. Measurements of Mass.
|
|
|
Grams |
|---|---|---|
|
|
Mass of evaporating dish |
|
|
|
Mass of a watch glass |
|
|
|
Mass of a large test tube |
4. Compare your measurements with those of another group in the lab. How do they compare and explain?
C. Measurements of Volume.
- Exact volume of water transferred from the beaker into the 100 mL graduated cylinder:
- Were the volumes in the beaker and the graduated cylinder identical or similar? If not, explain:
- Exact volume of water transferred from large test tube into graduated cylinder:
D. Measurement of Mass and Volume of Unknown Solid.
Unknown Number or Letter:
Description of Solid:
- Mass of the unknown solid:
- Length of unknown solid:
- Width of unknown solid:
- Height of unknown solid:
- Volume of the solid (Show your work):
E. Measurements of Temperature
- Room temperature:
- Temperature of cold tap water:
- Temperature of hot tap water:
POST LAB QUESTIONS
1. Perform the following conversions, show your work:
a) 2.5 cm = ______inch
b) 5.2 L = _____mL
c) 5.25 kg = ______g
d) 25.2 °C = ______F
e) 27.2 °C = ______K
f) -21.0 °F = ______°C
2. What is the volume of a rectangular wooden block with a length, width, and height of 5.5 cm, 4.5 cm, and 3.5 cm, respectively? Show your work.
3. Convert the room temperature, cold, and hot water readings into degrees Fahrenheit (°F) and Kelvin (K). Show your work.
Please click here to access the Pre-Lab, Data Tables, and Post-Lab in Word or PDF format. Complete them and upload according to your instructor's instructions.