CHEM 2115
Experiment # 1
INTRODUCTION TO THE LABORATORY
OBJECTIVES: The goals of this session include (1) an introduction to the general chemistry laboratory and CHEM
2115 course policies and procedures, (2) safety instruction, (3) checking into lab lockers, (4) learning how to use
electronic balances, (5) learning how to measure volume accurately, and (6) determining the densities of two
different solutions.
SKILLS: Using a balance; making volume measurements; writing significant figures and units; determining density.
EQUIPMENT: Top loading balances, graduated cylinders, pipets.
REFERENCE: Chemistry: The Molecular Nature of Matter, Jespersen et al., 6th edition, Chapter 2
SAFETY AND DISPOSAL: Water samples and glassware used in these exercises present no special hazards. It is
appropriate to dispose of the liquids used in this experiment in the lab sinks.
INTRODUCTION: Starting a chemistry lab course involves becoming familiar with the lab setting, equipment and
instruments, potential hazards and safety procedures, and the use, cleanup and disposal of chemicals. It also
involves making and recording measurements and observations and reporting experimental results. In this week’s
exercises lab policies and safety equipment will be introduced and the lab drawer check-in procedure will be
discussed. Some lab use rules and safety information plus a list of equipment in each drawer are given in this
manual. During each experiment, students will record information into their lab notebooks and submit a report of
their results. Instructions for recording and reporting experimental observations are provided in this experiment and
on the course website.
Weighing with an electronic balance is a specific skill that will be used throughout the course. This week’s
exercises involve learning how to use one correctly. An additional goal is to learn about significant figures and units
as they relate to lab measurements. The number of significant figures in a measurement is determined by the
precision of the measuring device: some instruments can measure better than others. Both milligram and centigram
balances will be used to illustrate this concept. A milligram balance does not yield the mass of an object in mg, but
rather shows the mass in grams and allows it to be determined to the nearest milligram (+0.001 g). Reporting the
results with the correct number of significant figures will show how good the measurement is. Finally, results can
be reported in a variety of different units, including kilograms, grams, centigrams, milligrams, pounds, and ounces.
Using correct units is essential. Volume measurements, using graduated cylinders and pipets, will also be made.
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Here, too, it is important to use the proper number of significant figures and units when reporting the results.
Density (D) is defined as the mass (m) of a sample divided by its volume (V).
D =
m
V
Density is dependent on temperature and solution concentration, but is independent of sample size: a large sample
has the same density as a small sample. In this experiment, the densities of two different sugar water solutions will
be determined at room temperature using the experimentally measured mass and volume of a sample. Students will
enter their own data into the laboratory computer so that it can be included in the analysis of class data as part of
Experiment 2.
LABORATORY NOTEBOOKS AND REPORTS
Scientists and working professionals need to keep clear records of what they do and need to transmit the results of
their work to others. The daily records are contained in a laboratory notebook; the results are given in a laboratory
report.
The Laboratory Notebook: A laboratory notebook serves several purposes. The first is for your own reference.
To avoid forgetting any important information, the details of each experiment should be recorded in the notebook
when they are performed during the lab. The second purpose is so that someone else can review your work and
repeat it exactly. This is necessary in research and industry, where legal and financial consequences often hinge on
what is in a laboratory notebook. It is also necessary in a student laboratory. If a particular experiment does not
work well for you, the instructor would want to know why. Your detailed written procedure and observations can
give clues to what happened if an experiment fails.
One format for keeping a laboratory notebook is discussed below. Your instructor may have a different format for
you to follow. CHEM I Lab is the place to start keeping a laboratory notebook. A sample laboratory notebook
entry for Experiment 1 is provided on the course website. As you continue on to subsequent courses, the
importance and expectations about the laboratory notebook will increase.
The correct notebook for the laboratory is a bound book containing lined pages. These are available at bookstores
and stationary supply stores. A loose-leaf or spiral notebook is not satisfactory because the pages are easily lost. If
the pages in the notebook are not numbered, number them before using the book. Write your name and laboratory
section number on the cover of your notebook. Enter experiments consecutively in ink; use permanent blue or black
ink because your book will become splashed and stained with use.
Your notebook can become cluttered and illegible if an organized format is not observed. For this reason, certain
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conventions have been developed. At the top of the page, write the date on which the experiment was performed
and the title of the experiment. As you go along, leave plenty of space for notes that you might want to insert later.
Write clearly so that your instructor will be able to read and grade your notebook. If you make errors, do not rip out
the page or use whiteout. Instead, line out errors (or draw an "X" over the entire page) and go on.
Notebook Format for Experiments
1. Introduction. Give a brief introduction to the experiment in which you clearly state the purpose(s) of the
procedure. This should require no more than one-fourth of a page.
2. Experimental Plan. Construct a detailed outline of the experimental procedure. A bulleted or numbered list is a
useful approach. Do not copy the experimental procedure from the book but provide a summary of it. This is also a
good place to prepare necessary calculations. This section MUST be completed before coming to the laboratory.
3. Experiments and Results. In this section, write down what you actually do and observe during the experiment.
You should write this section while you are in the laboratory. Every measurement that you make should be written
here with the appropriate units when you make it, and observations should be entered as they happen. For some
experiments, it will be helpful to have a table prepared to enter measured values. Templates of these tables will be
provided in the some of the experimental instructions.
4. Conclusions. Record the conclusions that can be reached based on the results you have obtained in the
experiment. It is appropriate to include calculations that are made during the lab in this section.
Laboratory Report Forms: The lab report is a summary of experimental results and conclusions. In CHEM I Lab,
the reports will follow a specific format, providing observations made, experimental data, and calculated results.
For some experiments, students will be asked to analyze class data and compare their own results to their class
averages. The reports will also include answers to questions asked about the laboratory. In subsequent courses, the
laboratory reports will shift to different formats, which include abstracts of experiments and conclusions about them.
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EXPERIMENTAL PROCEDURE
Your instructor will demonstrate how to use a balance, a graduated cylinder, and a pipet. Your goal should be to
learn how to use this equipment correctly.
I. Safety: As part of the safety introduction, be sure to know where the exits, eye washes, and showers are. If you
have a medical condition or take medication that could affect your performance, please inform your lab instructor.
This information will be kept confidential and be used only to maintain a safe working place
II. Lab Drawer Check-In: Check into the lab drawer, making sure that all of the listed equipment is there. Each
individual is responsible for the contents of his/her drawer and will need to bring the key to lab each week.
Approved goggles can be purchased from the College Bookstore and stored in the lab drawer during the week.
III. Mass and Volume Measurements
IIIA.
Mass: Determine the mass of ONE of the objects found next to the balance. The result should be within
+0.003 g of the posted value. Record the mass in your lab notebook, being sure to include the correct units.
IIIB.
Significant Figures and Units: Determine the mass of your 10 mL graduated cylinder on a milligram
balance (accurate to 0.001 g or 1 mg) and then on a centigram balance (accurate to 0.01 g or 1 cg). Record
the mass in each case. The number of significant figures should be different (because the sensitivity of the
two instruments is different). Each of these measurements may be expressed in other units. As an exercise,
write these measurements in kilograms and milligrams, being careful to label the answers and to use the
correct number of significant digits. Reporting the answer in either standard or scientific notation is
appropriate in this case.
IIIC. Volume: Determine the volume of liquid in a 50 mL and in a 10 mL graduated cylinder found in the fume
hood. Each of these can be read to a different precision. Your results should be within + 0.01 mL for the
10 mL graduated cylinder.
IV.
Density
Density is a physical property of a substance that relates its mass and volume. Knowing the mass and the
volume of a substance enables the density to be determined using the procedure below. You will determine
the density of two different sugar solutions
Place approximately 30 mL of Solution A into your 50 mL
graduated cylinder. Record the mass of an empty 50 mL beaker using the mg balance. It is important to
enter and label the data you take in your lab notebook. Carefully pipet 5.00 mL (using a 5 mL volumetric
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pipet) of sugar Solution A into the beaker. Record the mass of the beaker and sugar solution. Add a
second 5.00 mL aliquot (portion) to the beaker and again record the mass (The beaker now contains 10.00
mL of solution). Continue this until you have added a total of 25.00 mL of Solution A to the beaker. Clean
your pipet and beaker.
Obtain 30 mL of sugar Solution B in your clean graduated cylinder. Repeat the procedure used for
Solution A with Solution B.
ANALYSIS OF THE EXPERIMENTAL DATA
Enter your mass and volume data for both solutions into the lab computer, for use in class data analysis as part of
Experiment 2. Find the density of each trial by determining the mass of each 5.00 mL portion added, and then
dividing the mass by the 5.00 mL volume. The average density of each solution will be included in the Lab Report.
Using graph paper (available from the Blackboard site for this course), plot the Total Volume on the X axis and the
experimental Mass of Beaker + Solution A on the Y axis. With a straight edge, draw the best straight line through
these points. The line fits the form for a linear equation Y = mX + b. Find the slope and the intercept of the line.
Add points for Mass of Beaker + Solution B to the same graph that you prepared with the data for Solution A.
Draw the best straight line through these points and then find the slope and intercept of the line. This graph and the
values of the slope and intercept will be used to answer questions in the Lab Report.
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NOTEBOOK TEMPLATE
(This template represents the minimum information needed for the experiment. It should be copied into your
notebook and used to record data during the experiment.
observations into your notebook as you do experiments.
In addition it is important to add comments and
A complete sample notebook entry for Experiment 1 is
provided on the course website. DATA IS NOT RECORDED IN YOUR LAB MANUAL, ONLY IN YOUR
NOTEBOOK.
Lab Station Number __________
IIIA
IIIB
Mass of object
g
Posted value of object
g
IV
(milligram balance)
Significant Figures and Units: Mass of 10 mL graduated cylinder
milligram balance
IIIC
Lab Drawer Number
g
centigram balance
g
Volume of a liquid
in a 50 mL graduated cylinder
mL
posted value
mL
in a 10 mL graduated cylinder
mL
posted value
mL
Density
Total
Volume
Solution
1. Empty Beaker
2. Beaker + 5.00 mL
3. Beaker + 10.00 mL
4. Beaker + 15.00 mL
5. Beaker + 20.00 mL
6. Beaker + 25.00 mL
mL
0
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Mass of Beaker
and solution
A
B
g
g