Download Working in a Lab

Working in a Lab
Lab Safety 021
Measurements 053
Glassware & Microscopes 046
Some Rules for Working in the Lab
Glassware Safety
Glassware is vital to doing good science. If not handled with care, glassware can cause serious harm. Notify your teacher if
you break glassware. Dispose of broken glass in the appropriate container. Remember that to use such equipment is a
privilege.
Sharp Instrument Safety
Sharp instruments are needed in the lab. You must never use or pretend to use it on yourself or someone else. Remember
that to use such equipment is a privilege.
Eye Safety
Often labs require that you wear safety glasses. The purpose of such glasses is to prevent damage to your vision. If
something should get into your eyes, make sure you let your teacher know. The glasses shown here are for impact safety.
Safety goggles that are vented should be used when working with chemicals. Alcohol wipes should be used to clean the
goggles before using. Remember that to use such equipment is a privilege.
Electrical Safety
Many labs involve the use of electrical devices. When you plug in such electrical equipment, make sure you include the
ground plug (round). Hold the plug firmly by the insulating cover when plugging it in or unplugging it. NEVER unplug an
electrical device by pulling on its cord! Remember that to use such equipment is a privilege.
Chemical Safety
Often labs involve the use of chemicals. Please be careful to keep chemicals off your skin and out of your mouth and eyes. If
you get any chemical on your skin or in your eyes, INFORM your teacher immediately! Remember that to use such chemicals
is a privilege.
Microscope parts
Using a microscope
• Your microscope has 3 magnifications:
Scanning, Low and High. Each objective will
have written the magnification. In addition to
this, the ocular lens (eyepiece) has a
magnification.
• The total magnification is the
ocular x objective
When you look through
the eyepiece, the lighted
area you see is the
FIELD OF VIEW.
Magnification
The eyepiece lens has a magnifying power of 10x. The objective lens being used has
a magnifying power of 4x. To find the total magnification, multiply these two
numbers:
Measurement
• A measurement is a repeatable observation of
quantity that includes a number and a unit.
An estimate is a reasonable guess at a
quantity based on an observation.
The water
took a long
time to boil.
The water took
almost a quarter
hour to boil.
The water
took exactly
18 minutes
to boil.
SI system
• SI system of measurement stands for
“Systeme International” which is French
for International System. It is also called
the Metric System.
Base Units
Quantity
Unit used in SI (symbol)
Length or distance
Meter (m)
Volume or capacity
Liter (L)
Mass
Gram (g)
Density
Gram per cubic centimeter (g/cm3)
Time
Second (s)
Temperature
Degrees Celsius (C)
Measuring Liquid Volume
1.
2.
3.
4.
Pour liquid into a graduated
cylinder.
Move your head so the top of
the liquid in the cylinder is at eye
level.
Look for the meniscus, the
curved surface of the liquid. You
may find it easier to see the
meniscus if you hold a sheet of
white paper behind the
graduated cylinder.
A water meniscus is about as
thick as a nickel. Read the
volume at the bottom of the
meniscus. If the volume is
between two marks on the
cylinder, estimate the volume.
Volume of Rectangular Solids
• The cubic centimeter (cm3 or cc) is a common
unit of volume. It is usually used to measure
the volume or capacity of a rectangular solid,
or box. The volume of a box equals its length
times its width times its height.
Volume = length x width x height
V=L x W x H
Triple-beam balance
Mass
Rear weight is in the notch reading...... 70 g
Middle weight is in the notch............... 300 g
Front beam weight reads....................3.34 g
The object weighs............. 373.34 g
Density
1. Know the simple mathematical formula for
calculating the density of a substance. To use
this formula, you will have to know the mass
and the volume of the substance. The mass
refers to the gravitational pull on the
substance and how much matter it contains.
The volume refers to the amount of threedimensional space the substance occupies.
Step 2
• Calculate the volume of the substance by
measuring the length, width and height. The
formula looks like this: Volume = L (length) x
W (width) x H (height).
Step 3
If the object or substance is
irregularly shaped,
determine the volume by
finding out how much
water is displaced when
the object is dropped into a
beaker of water.
Next…
Calculate the density
once you know the
volume and mass of
the substance or
object. Density is
equal to the mass of
the substance
divided by its
volume: D (density)
= M (mass) / V
(volume).
Will it float?
• Know that a substance or object with a higher
density has a higher measure of mass per unit
of volume. A substance with a density that is
greater than 1 g/cm cubed will sink in water
because it is denser. A substance with a
density below 1g/cm cubed will float because
it is less dense than water whose density is
approximately 1 g/cm cubed.