The Nature of Science: Unit 1A
Safety, Equipment, and
Measurement
Safety
Safety Rules: The Big Ones
1. Pour acid into water slowly (PAWS)
2. Tie your hair back
3. Wear goggles and an apron when
working with chemicals, fire, or glass
4. Wear gloves when working with
chemicals and bacteria
5. Don’t pour unknown chemicals down
the sink, or return them to unlabeled
containers, etc
Important Safety Terms & Symbols
1. Corrosive- Will corrode or eat away
metal, skin, or other substances.
2. Volatile- Evaporates quickly, may form
dangerous vapors
3. Flammable (may ignite)- will catch on
fire or explode easily.
4. Ventilation- removing contaminated air
and brining in fresh air
Corrosive
Flammable
Poisonous
Explosive
Lab Safety
Corrosive
material
This is the safety symbol for ____________
This picture indicates that the chemical
represented is —
A pressurized
B corrosive
C flammable
D toxic
Correct answer: Choice B
Lab Safety
Reactions that produce toxic gases should be
performed in a —
Should we breath in toxic gases? NO!
How can we trap toxic gases?
A
B
C
D
laboratory fume hood
beaker with a watch glass on top
well-ventilated area of the lab
warm, airtight drying oven
Correct answer: Choice A; a lab fume hood will
trap the gases so that we don’t breath in the fumes
from the toxic gases!
Heating Chemicals in a Test Tube--When a 10% hydrochloric acid solution is heated
in an open test tube, the test tube should always
be pointed —
Safety rule: Always
A so bubbles are visible
point test tube away
B at a 180° angle from the
from yourself and
others
flame
C toward a ventilated area
D away from nearby people
Correct answer: D Choice D BEST matches
our safety rule
Wafting Chemicals
The reason for wafting or fanning a small amount
of chemical vapors toward the nose as a means
to detect odors in a test tube is to —
A avoid experimental error from excessive loss of mass of reactants or
products
B avoid splashing chemicals into the face of any person
C protect the respiratory tract against potentially harmful vapors
D determine the relative strength of the odor before smelling directly
Correct Answer: C; wafting allows a small amount of the chemicals
vapors to be detected by your nose without you having to smell the “full”
odor.
Lab Equipment
Common Equipment
1. Be familiar with common lab equipment
and their uses.
2. Be able to read measurements
accurately and in metrics.
3. Be able to chose the BEST equipment
that would help achieve the desired
results in an experiment.
4. Be able to chose equipment that will
give the MOST precise results.
Which is MORE precise, the
graduated cylinder or the beaker?
Graduated cylinder
because it has units in
increments of 1 mL
Graduated cylinder:
measures volume
Triple beam
balance:
measures mass
Beaker: measures
large volumes of liquids
Accuracy verses Precision
Accuracy:
1. The accuracy of the instrument refers to how close the
measured value is to the true or accepted value.
2. For Example : if an object has a real mass of 2 grams
and the balance used gives a reading of 2 grams, the
measurement is accurate. If the balance reads 1.8
grams it is inaccurate.
Precision:
1. Precision refers to how close together a group of
measurements actually are to each other.
2. For Example: If an object has a true mass of 2 grams. A
person masses it as 5 grams three time in a row. The
person shows precision (but NOT accuracy)
Choosing Equipment
Which piece of equipment would
be used to precisely measure
the volume of an acid?
Precisely – want lots of
increments
Volume – need something
that measures in mL
Correct answer: Choice C
because the graduated
cylinder gives a more
precise measure than the
beaker.
Eliminate choice A (balance measures mass) &
D is a Bunsen burner
Measuring Accurately
The illustration shows
volume levels of a liquid
in a graduated cylinder
before and after a
sample was removed.
According to this
information, what was
the volume of the
sample to the nearest
milliliter?
Record and bubble in your
answer on the answer
document.
Meniscus
47 mL
38 mL
Subtract: 47mL – 38 mL = 9.0 mL
The meniscus is the slightly curved surface that forms in a graduated
cylinder. Always read at the bottom of the meniscus.
Reading a Burette
Which is the best
estimate of the
volume of solution
released from the
burette?
A 47.3 mL
B 47.7 mL
C 48.3 mL
D 48.7 mL
Correct answer: B
Initial volume
0.8 mL
Final Volume
48.5 mL
Final volume – Initial volume =
47.7 mL
48.5mL – 0.8 mL =________
Choosing Appropriate Lab Equipment
An experiment was conducted to test the
effectiveness of four different fertilizers on plant
growth. Two grams of each fertilizer were to be
diluted in 9 milliliters (mL) of water before adding to
a plant. Which of the following measuring devices
would introduce the least error into the
measurement of the 9 mL of water?
F 10 mL graduated
cylinder
G 20 mL graduated
cylinder
H 50 mL graduated
cylinder
J 100 mL graduated
cylinder
Use the graduated cylinder that
holds the least volume that is
required to ensure the least error
(most precise) measurement.
Correct Answer: F Choice F
holds the least volume