Some Common Lab Techniques
Massing solids: When obtaining the mass of
solid chemicals, always use some type of weighing paper to protect
the pan of the balance. Remember that the mass of the weighing paper
must be written down and subtracted from the total weight when you
are determining the amount of solid obtained.
Measuring liquids: When measuring out a particular
volume of a liquid, you must choose an instrument that will measure
as accurately as possible. For small quantities it would be appropriate
to use a pipette or burette. For larger quantities a graduated cylinder might
be appropriate. Remember that beakers are not accurate measuring
instruments! Remember always to take measurements of liquids from
the bottom of the meniscus.
Filtering: When filtering a solid from a
mixture by gravity filtration, always weigh the filter paper, fold
it, place it in the funnel, and wet it down to hold it in place
before beginning the filtering process. After filtering, the solid
on the filter paper must be dried and weighed. The initial weight
of the filter paper is subtracted to find the mass of the solid obtained.
The liquid that comes through the filter paper is known as the filtrate.
One way to identify elements is by performing a simple
flame test in the laboratory. When the electrons are heated, they
get excited and jump away from the nucleus. As they fall back down,
they release energy, often in the form of visible light. Some of
the most common colors of flames are listed. You may recognize many
of these from fireworks displays!
Many solutions in chemistry also have color, which is
often the result of unpaired electrons. Metal ions often are colored.
||Yellow to orange (rusty)