Practice 1: Recognition of laboratory materials, mass measurements and

volume.

Objective
Identify and understand the usefulness of the most commonly used instruments and equipment in the
General Chemistry Laboratory.

Start
Laboratory instruments are made up of various materials and it is necessary
that before starting any experimental work, the student knows the material that
It will be used. Improper use of this material leads to errors in the experiments.
performed and increases the risk in the laboratory.

Laboratory materials are classified into:

Volumetric: This group includes calibrated glass materials;
they allow measuring volumes of substances.
• Heating or support: These are used to carry out mixtures or reactions and
which can also be subjected to heating.
Measuring equipment: These are instruments used to compare physical magnitudes.
through a measurement process. Objects and events are used as units of measurement.
previously established as standards or patterns. The measurement results in a number
What is the relationship between the object of study and the reference unit. The instruments of
measurement is the means by which this conversion is made.
Special equipment: They are auxiliary equipment for laboratory work.

Below are some of the laboratory materials and their uses.

Laboratory materials

Name and Use

Erlenmeyer flask: it is used to heat liquids with little loss by evaporation,
perform titrations and recrystallization of solid.
Vacuum flask: it is used for vacuum filtrations with a suction pump.
Round-bottom flask: allows for the containment of substances and can be heated. It has a round bottom or
flat and is used with other materials to form equipment.
Distillation flask: these are flasks with a side tube that allow circulation of
vapors in distillation (where it is used with the condenser).
Evaporating dish: used to dissolve substances, heat liquids, and collect.
filtered.
Graduated flask: volumetric material used to prepare solutions. They have a mark or
gauge on the neck that indicates the volume of the contained liquid. There are various sizes:
100mL; 250 mL; 500 mL; etc.
Graduated cylinder: it is used to measure approximate volumes of liquids. It has a wide range.
of capacities (5 mL, 100 mL, 1 L, etc). They are available in glass or plastic. They cannot be
to heat
Separation funnel: it is used to separate immiscible liquids.
Graduated burette: it is used to titrate solutions.
Volumetric Pipettes: measure exact volumes of liquids.
Test tubes: Containment material. They can be heated to carry out reactions in
small scale. They come in various sizes.
Funnel: it is used to filter substances. It can be used to transfer liquids. There are
glass or plastic.
Watch glass: it is used to weigh solids, cover beakers, and evaporate drops.
of volatile liquids.
Refrigerant tubes: An instrument formed by a glass tube and an interior spiral inside.
Through which a current of cold water circulates that causes the condensation of vapors.
Spatulas: they are used to take small amounts of solid samples.
Buchner funnels: it is used for suction or vacuum filtration.
Crucibles: they are used to calcine substances.
Porcelain crucible: it is used to heat substances and evaporate liquids. It allows the
heating of substances at high temperature.
Mortar and pestle: it is used to crush solids with a pestle and to mix substances.
They are made of glass or porcelain.
Universal support: allows holding various materials along with nuts. Attached to clamps,
they allow the assembly of different teams.
Bunsen burner: it is used to heat substances. It is necessary to regulate the intake of
air to achieve a well-oxygenated flame (blue flame).
Crucible tongs: they are used to place and remove crucibles that have been heated.
intense warming.
Tripod: it is used over the burner to heat.
Tube brush: it is used to clean test tubes.
Metal rings: they are used to place funnels and separation balloons.
A stand is used to hold test tubes.
Desiccator: equipment provided with a frosted lid and a porcelain disc that serves as
support for the containers placed inside. It is used to absorb moisture from
the precipitates, dry solids and keep the medium dry.
Thermometer: an instrument used to measure temperatures.
Analytical balance: instrument used in quantitative analysis to determine quantity
of mass with a precision of 0.0001 mg.
Extraction hood: it is designed to efficiently extract toxic vapors,
harmful and other volatile hazardous materials from the work area.
Oven: tool for drying solids. Handles temperatures of up to 1500°C.

Practice.

Observe and analyze the information presented in the table. Classify the materials or equipment.
from the laboratory according to the categories mentioned above (volumetric, heating or
support, measuring equipment and special equipment.
 Name of instrument Category

Name of the instrument

a. Measures of mass and volume: experimental work requires comparing magnitudes;
for this it is necessary to use the appropriate instruments and a unit of measure
that is taken as a basis for comparison between them, considering accuracy,
possible margins of error and handling of significant figures.
b. Balance. The instrument used to determine the amount of matter of a
substance in the laboratory is the balance. The unit in which it is measured in balances
it is the gram or a multiple or submultiple of it. There are many types of
balances, but in laboratories analytical (electronic) ones are currently used and
the granaries. The advantage of electronic scales is that regardless of
of its accuracy, all are used in a simple and clear manner. It is convenient
knowing that the mass of the container in which a measurement is to be made is referred to as
carry out the operation of zeroing the scale reading with the container
included, it will be called. The analytical balance is used when needed.
precision in measurement, and the granularity when it is not.
c. Reading of volumes. The free surface of the liquids is horizontal, however,
generally curves upward in contact with the walls of the container that
it contains them forming a concave meniscus, like in water. The readings must be
to carry out at the bottom of the meniscus placing the eye at the same level as it
avoid parallax errors. When the meniscus is convex (in the case of mercury
about glass), the reading should be done from the top.
d. Measurement with a pipette. The pipettes should be filled with a pipette aid for
avoid accidents caused by raising the liquid above the upper gauge.
One should never suck with the mouth; neither should the assistant be left in place.
the pipette after using it, nor leave the pipettes inside the bottles. It is necessary
remove them when finished using them. There is usually a small volume left in the pipettes.
liquid at its tip, that portion is constant and in its graduation it has already
it has been calculated; it should not be shaken or blown to remove that excess.
The pipettes should not be placed on the table; they should be placed in a stand.
measure with pipettes, follow the following instructions:
Carefully observe the pipette locating the maximum and minimum volume.
Insert the pipette into the container with the liquid and place the assistant.
Suck up the liquid, making sure it does not exceed the graduated scale.
Hold the pipette vertically and let the excess liquid flow until it reaches the
zero mark.
Let part of the liquid fall while reading the new volume on the graduated scale.
e. Measurement with a graduated cylinder. It is used for measuring larger volumes of
liquid.
Activities.
Measure 100 mL of water with a graduated cylinder and transfer it to a 250 mL beaker.
mL.
Using 3 test tubes placed in a test tube rack, transfer volumes of 5 mL.
7mL and 10 mL, using the appropriate pipettes.
Weigh 0.001 g, 0.01 g, and 0.0001 g of common salt (NaCl) using the materials.
suitable.

Evaluation
a. What is the difference between refractory material and non-refractory material? (Give examples and
explain its uses and characteristics
b. What is the difference between a calibrated material and a volumetric one? (Give examples and
explain its uses and characteristics).
c. What is the difference between weighing and measuring? Explain clearly.
d. Organize the 'frames' of the flame and explain the reason for the image in each one
in detail.