Lab Procedures Introduction
OHS Chemistry
Name:
Date:
Period:
Purpose: To introduce lab equipment and lab techniques that will be used throughout the year and emphasize
the importance of accuracy in measurement. In addition, students will learn how to read and interpret chemical
safety information.
Hypothesis: Using an If– Then – Because format, predict which of the three devices in procedure B2 will most
accurately measure the water volume.
In a second sentence, using the same format, predict how the final mass (box e) of NaCl in procedure B3 will
compare to the original value (box a).
Procedure:
A. Using the materials provided at the lab station, practice the following techniques that were demonstrated to
you earlier. Be prepared to demonstrate your technique to the teacher.
1) Transferring solids; transfer samples of salt into a test tube, using creased paper.
2) Pouring a liquid (water) into a beaker using a stirring rod to direct the stream of flow.
3) Pouring a liquid into a test tube using a test tube holder to prevent spilling the chemical on your
hands.
B. Using the tables in this section, follow procedures and record the appropriate data.
1) Measure directly the mass of a penny, an empty 250 milliliter (mL) beaker and an object of your
choice.
Object
Penny
Empty 250 mL beaker
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mass (g)
2) Determine the mass of the water using the technique of “measurement of mass by difference” outlined
here:
i.
Find the mass of a clean, dry 100 mL beaker. Record your data.
ii.
Measure out 65 mL of water, using the 100 mL graduated cylinder.
iii.
Transfer the water into the dry 100 mL beaker
iv.
Re-measure the mass of the beaker with the water in it. Record results.
v.
Calculate the mass of the water from your data. Record.
Repeat the procedure with each of the other two pieces of lab equipment (a 10 mL graduated cylinder
and a 250 mL beaker).
Measurement Device
Mass of clean,
dry 100 mL
beaker (g)
Volume of
H2O (mL)
100 ml graduated
cylinder
65
10 ml graduated
cylinder
65
250 ml beaker
65
Mass of H2O &
Beaker
Mass of H2O
(g)
3) Read the following procedure carefully. Then, in the chart below label the procedure descriptions
clearly using the procedure steps as a guideline. The first two are done for you.
Follow this procedure exactly. Not all beakers of the same size have exactly the same mass and because you
are using more than one beaker, be sure they are all clean and dry and that you know both of their masses.
a) Using the technique of “mass by difference” measure the total mass of NaCl in your beaker. Record.
b) Measure out exactly 2.31 grams of NaCl from the original beaker (in part a) and transfer it to a
second dry beaker. Record the mass of the NaCl removed.
c) Measure out an additional 5.45 grams of NaCl into the same dry beaker as in part b. Again, record the
mass of the NaCl removed.
d) Now, using the technique of “mass by difference”, measure the mass of NaCl remaining in the
original beaker. Record.
e) Total the three quantities of NaCl from parts b, c, and d. Record in section ‘e’.
Mass of clean, dry beaker #1 (g):
Mass of clean, dry beaker #2 (g)
Procedure Description
a) Total mass of NaCl
b) Mass of NaCl removed in step (b).
c)
d)
e)
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Mass of beaker
and NaCl (g)
Mass of NaCl
(g)
C. 1) Four chemicals in their original containers have been placed out in the lab. Using the information on
their labels, answer the following questions in a complete manner:
a) Which of the chemicals is/are flammable?
b) Should you use goggles when handling glycerin? How do you know?
c) What is the first aid procedure for external exposure to potassium nitrate?
d) Which of the chemicals is least toxic (health hazard rating)? What does the rating mean?
e) What is the chemical formula for glycerin?
f) List the four chemicals in increasing order of reactivity.
2) Using the internet, search for the Safety Data Sheets (SDS) for each of the following chemicals and
answer the questions:
a) What hazards are identified in handling the chemical ammonium hydroxide?
b) If there were an accidental release of aluminum sulfate into an area, what steps should be taken?
c) The toxic (toxicological) effects of mercury affect which organs of the body?
Conclusion: To be typed as part of the write-up and attached to this lab paper
a. Look at the data from Procedure B2 where you measured water using different devices. What
conclusion can you draw about the relationship (think ratio) between the mass of the water (in grams)
and its volume (in mL)? In a paragraph, write a conclusion, stating your claim, the evidence for the
claim and the reasoning used in drawing the conclusion.
b. Read your first hypothesis, and decide whether or not it was supported by the data. Again, write a
statement including a claim, some evidence and reasoning for your statement.
c. In a separate paragraph, address the second hypothesis using the same format and the data from
Procedure B3.
Discussion: Finally, explain what this experiment teaches about the importance of accuracy of measurement in
chemistry. Give specific examples from the lab which illustrate your conclusion.
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Glycerin
Barium chloride
Phenolphthalein
Potassium nitrate
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