Experiment 3.1
Observing Chemical Changes (4)
Lab Report = 72
(5) Introduction:
In chemistry you should be watching for
changes when you do lab experiments. Some
changes will be obvious, such as dramatic color
changes. Some will be almost undetectable, as
in the slow reaction of oxygen with iron to form
rust. Sometimes there will be no change at all,
but this observation of “no change” is as
important as observations of change.
All matter is either solid, liquid, or gas at room
temperature. If two liquids are mixed, and a gas
is produced, a chemical reaction has occurred.
Likewise, if two liquids are mixed, and a solid is
produced, a chemical reaction has occurred. If a
color change is observed or a change in
temperature occurs without adding or removing
heat, these are chemical changes as well.
However, if a solid simply changes into a liquid
as when ice melts, this is a change in the phase
of matter. It is a physical change, not a chemical
reaction.
It is important that the observations that you
make in the lab be as specific and informative as
possible. Whenever possible, try to quantify the
changes you observe. If you think the mass has
decreased, use available equipment to find out
how much the mass has decreased. If you
observe “material became hotter,” use a
thermometer to determine how much the
temperature changed.
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(2) Objectives:
1. Observe chemical and physical change.
2. Present and explain observations of
changes accurately and completely.
3. Identify and use appropriate lab equipment
necessary to quantify observations.
4. Recognize patterns in observations.
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Apparatus:
centigram balance
spot plate
4 - 13 X 100 mm test tubes
test tube rack
stirring rod
100 mL beaker
safety glasses or goggles
laboratory apron
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(5) Reagents:
ammonium chloride
sodium bicarbonate
calcium carbonate chips
sodium hydroxide pellets
0.1 M lead(II) nitrate solution
0.1 M potassium iodide solution
1.0 M acetic acid solution
0.1 M sodium hydroxide solution
0.1 M sodium carbonate
0.1 M calcium chloride
1% phenolphthalein solution
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Procedure:
1. Adorn your safety glasses and lab apron.
2. In this experiment you will be asked to make
observations. While you are making
observations, think about how they might be
quantified. Be careful to note the phase of
matter you are asked to use.
3. Using the 13 X 100 mm test tubes, mix the
following pairs of reagents in the quantities
listed. Mix each concoction by stirring with
stirring rod. Use a microspoon to add each
Experiment 3-1
solid. Rinse and dry between each use. To
make sure you feel a temperature change, hold
the test tube near the top.
a. ≈1 gram ammonium chloride + ≈5 mL water
b. ≈1 pellet sodium hydroxide + ≈5 mL water
c. ≈1 gram sodium hydrogen carbonate + 5 mL
acetic acid
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d. ≈1 gram calcium carbonate + 5 mL acetic
acid
c. 5 drops of sodium carbonate + 5 drops of
calcium chloride.
4. Using a spot plate, mix the following reagents in
the amounts listed.
e. 5 drops lead nitrate solution + 5 drops
potassium iodide solution.
a. 5 drops sodium hydroxide solution + 1 drop
phenolphthalein solution.
5. Record all observations on the data table.
6. If in doubt on any part, repeat that part.
b. 5 drops acetic acid solution + 1 drop
phenolphthalein solution.
7. Clean up all materials and wash your hands
thoroughly.
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Data and Observations: (20)
(10)
(10)
Data Table
Chemicals Used
ammonium chloride and
water
Sodium hydroxide pellets
and water
sodium hydrogen carbonate
and acetic acid
Calcium carbonate and
acetic acid
Stamp for 4
tubes.................
sodium hydroxide and
phenolphthalein
acetic acid and
phenolphthalein
Sodium carbonate +
Calcium chloride
Lead(II) nitrate + potassium
iodide
Stamp for 5
wells..................
Observations
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(18) Analysis and Conclusions:
(8) 1. Describe in clear terms how each step of the
procedure could be repeated to collect
quantified data.
a. ammonium chloride + water
b. sodium hydroxide and water
c. sodium hydrogen carbonate and acetic
acid
d. calcium carbonate and acetic acid
e. sodium hydroxide and phenolphthalein
f. acetic acid and phenolphthalein
g. sodium carbonate + calcium chloride
Experiment 3-1
h. lead(II) nitrate + potassium iodide
(3) 2. Describe any temperature changes you
observed.
(2) 3. Describe any color changes you observed.
(2) 4. Which combinations produced a gas?
(2) 5. Which combinations produced a precipitate?
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(1) 6. Which combinations resulted in no reaction?
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(18) Synthesis:
1. Based on your observations, predict the results
of mixing the following pairs of chemicals.
Explain why you are making a particular
prediction. If you cannot make a particular
prediction, tell why.
(4) a. magnesium carbonate + acetic acid
i. prediction
ii. explanation
(4) b. ammonium hydroxide + phenolphthalein
i. prediction
ii. explanation
(4) c. lead nitrate + sodium chloride
i. prediction
ii. explanation
Experiment 3-1
(4) d. hydrochloric acid + sodium hydroxide
i. prediction
ii. explanation
(2) 2. Suppose you wanted to collect and find the
mass of a gas produced in a chemical reaction.
How would you do it?
Extra Credit: (10)
Write and balance the complete reaction between
sodium hydrogen carbonate and acetic acid, calcium
carbonate and acetic acid, sodium carbonate and
calcium chloride, and lead(II) nitrate and potassium
iodide.
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