Principles of Chemistry I Lab Montgomery College
Rockville Campus
LABORATORY EQUIPMENT REFERENCE GUIDE
Balance
Balances are used to determine the mass of an object. Six are present
throughout the laboratory. You may place a piece of glassware or weigh
oat on the balance pan, then press ‘O/T’ to zero (tare) the balance.
Always record all numbers on the readout in your lab notebook and use
the same balance throughout an experiment.
Beaker
You have several of these in your drawer in different sizes. They are an all-
purpose laboratory container. The volume markings on the side are
imprecise, so quantities of a liquid should be measured with the graduated
cylinder and transfe
ed to the beaker, rather than measured with the
eaker itself.
Laboratory Burner
A Bunsen burner uses a flame to supply heat. To use a Bunsen burner,
connect it with latex tubing to the gas supply on the bench. Turn the
gas valve so that it is parallel to the hose, then use a striker above the
opening of the burner to ignite the flame. Valves at the bottom of the
urner can be turned to adjust the flame to a blue color and well-
defined shape. The burner can be handled from the base to move it
into place under the beaker or flask to be heated. Turn off the burner
y moving the valve so that it is parallel to the nozzle. Bunsen burners
are located in the shared equipment drawers by the window.
Büchner Funnel
A Büchner funnel is used in vacuum filtration. The Büchner funnel
is fitted with flat filter paper and placed on top of a side-arm flask.
The solution is poured into the funnel. Crystals or other materials
are collected on the filter paper, and the filtrate passes through
to the side-arm flask.
Buret
A buret is filled with a solution and suspended above an Erlenmeyer flask
using a ring stand. By gently opening and closing the stopcock, small and
precise quantities of the solution can be added to the flask. Your eye should
e level with the liquid in the buret for an accurate measurement. By
interpolating the volume readings between the lines, you can obtain volume
measurements accurate to two decimal places.
Crucible
A crucible is a small ceramic container used to hold powdered
materials and other solids. The crucible can withstand higher
temperatures than glassware, so it is used when heating certain
chemicals with the Bunsen burner.
Deionized Water
Tap water contains several impurities, such as magnesium, calcium, and
fluoride ions. These ions can interfere with certain reactions, so when water
is needed for a solution, deionized water is used. You should also rinse your
glassware with deionized water after washing it. Deionized water can be
obtained from the equipment located at the sink by the exit.
Desiccator
A desiccator is a small container containing a desiccant, which removes
moisture from the air. Thus, the air inside a desiccator is very dry. A
chemical is placed inside a desiccator when it can abso
water in order
to prevent it from reacting with the atmosphere. They are found on
shelves along the laboratory wall.
Erlenmeyer Flask
Several of these are present in your lab drawer. The flask and the beaker are
the two vessels used to contain most of the chemical reactions taking place in
the lab. The shape of the flask allows its contents to be swirled while
minimizing the possibility of spills. The markings on the side show the
approximate volume, but they are imprecise, so Erlenmeyer flasks should
never be used to measure quantities of a liquid.
Graduated Cylinder
The graduated cylinder is used to measure the volume of a liquid, which is then
typically transfe
ed to a beaker or flask. To use a graduated cylinder, place it on the
ench, crouch down so your eye is level with the liquid, and read the scale from the
ottom of the meniscus (the curve of the liquid). Never hold the graduated cylinder
up off the bench as it leads to e
oneous measurements. You should interpolate the
measurement between the numbers as best you can. Chemicals should not be mixed
in a graduated cylinder, and it should never be heated with the Bunsen burner.
Hot Plate
Hot plates are used to heat a reaction vessel such as a beaker
or Erlenmeyer flask. They are primarily used for gentle heating
or for when the reactants are flammable and should be kept
away from the open flames of the Bunsen burner. Hot plates
are located on shelves at the end of each row of lab benches.
Never put away a hot plate while it is still warm, as the heat
may melt the sleeve of the electrical wires.
Ring Stand
The ring stand holds laboratory equipment in place. When using a Bunsen
urner, the flask or beaker is placed on a piece of wire gauze, which rests on
a ring attached to a ring stand. A second ring is used to su
ound the beaker
to protect against spills. The burner is then ignited and placed below the
gauze. Clamps can also be attached to the ring stand to hold thermometers,
urets, or other equipment.
Scoopula
The scoopula in your drawer is used to
transfer powders, crystals, and other
solids.
Side-arm Flask
A side-arm flask is used in combination with a Büchner funnel in vacuum
filtration. The side-arm is connected to a vacuum with vacuum tubing. When a solution is filtered,
crystals or other materials are collected in the Büchner funnel, while the
filtrate is collected in the side-arm flask.
Sti
ing Rod
These long, thin pieces of glass are provided for when a liquid needs to be sti
ed.
Never use thermometers, pipettes, scoopulas, or other equipment for this
purpose.
Striker
The friction from flint ru
ing against the metal coil in the striker
generates sparks which are used to light a laboratory burner.
Thermometer
Used to determine the temperature of a liquid. The bulb of the
thermometer must be completely submerged in the liquid, and
cannot be touching the wall of the container. Thermometers are
fragile, so never use them to stir a liquid. As with the graduated
cylinder, you must interpolate between the markings for the highest
precision. Thermometers are located in the shared equipment
drawers by the windows.
Tongs
Located in the shared equipment drawers, tongs are used to pick
up hot pieces of lab equipment. Crucible tongs can hold a crucible
in its curved area, or grip the lip of the crucible with the prongs.
The heavier duty beaker tongs are used for moving large beakers.
Volumetric Flask
A volumetric flask is cali
ated to one specific volume, and is used to prepare
solutions of a precise concentration. Unlike Erlenmeyer flasks, volumetric flasks
are not used as reaction vessels, so once the solution is prepared it should be
transfe
ed to a more appropriate container. Volumetric flasks of various sizes are
located on the shelves near the windows.
Weigh Boat
Weigh boats are one-time-use, disposable plastic containers used to transfer
a solid to a beaker or flask. Weigh boats are placed on a balance to hold the
solid while its mass is obtained. One end of the weigh boat is tapered to
allow the solid to be easily poured into the receptacle. After using the weigh
oat, dispose of it in the trash to avoid cross-contamination.
Wire Gauze
Wire gauze is placed under a beaker on a ring stand when
heating it with a Bunsen burner. The gauze helps to support
the beaker and distribute the heat from the burner evenly.
CHEM 131L Principles of Chemistry I Laboratory
The Scientific Method
Remote Instruction Version
Introduction
Chemists use the scientific method in order to develop a better understanding of matter. The first step
of the scientific method is to state the problem to be studied. The second step is to form a hypothesis,
which is a prediction of the outcome of an experiment. Thirdly, an experiment is designed and
performed with the purpose of confirming the hypothesis. Lastly, qualitative and quantitative data are
collected and analyzed, which often leads to the revision of the hypothesis, followed by a new
experiment.
This cyclical process usually involves many experiments. Experiments are repeated to ensure
eproducible results. Reproducible behaviors that are observed may become scientific law. Consider the
eaction of hydrogen with oxygen to form water, according to the equation, 2 H2 + O2 → 2 H2O. Many
experiments were conducted when mass ratios of 4.0 grams of hydrogen react with 32.0 grams of
oxygen. The data consistently showed that 36.0 grams of water are produced. Notice that the total mass
of the reactants is identical to the mass of the products. Experiments were repeated with other
eactions, and the results showed the total mass of the reactants is identical to the mass of the
products. These observations of behavior led to the law of conservation of mass. A law permits the
prediction of results based on previous behavior. A theory explains the reasons for the behavior.
This activity will provide you with the opportunity to practice utilizing the scientific method and to
develop your critical thinking and analysis skills.
Objective
In this activity, you will develop an experimental procedure to solve a problem. Consider the following
scenario:
You are the manager of a chemical stockroom, and find a bottle containing approximately one liter of a
clear and colorless solution of unknown identity and concentration. Your only clue to its identity is that
it was found between bottles of silver fluoride and sodium fluoride, so it is likely an aqueous solution of
one of those two compounds. You will need to develop a procedure to determine the following:
a) The identity of the unknown solution
) The concentration of the unknown solution
Write out a precise procedure, which includes all glassware, reagents, and steps. You will also need to
write the calculations that you would need to