Project #24: Name:_______________
Sect#_______
The Control Experiment
Demonstration
Author: John Taylor Fall 1996 @ HCC-Brandon with Michael and Mary
Ann
Background:
In the Fall of 1996,
Professor Taylor attempted to perform a controlled experiment in the
Hillsborough Community College Brandon Campus chemistry lab on a Fall day in
1996.
However, everyone was gone on that Friday afternoon, he had no keys to the
stockroom
and chemistry technician did not add all the equipment to the cart. The following
items were missing:
1. a Fisher Burner,
2. rubber tubing for the burner,
3. a triple beam balance,
4. Five metal spatulas or scoops,
5. several pieces of glassware.
The performance is
flawed because additional controls should have been demonstrated.
However, as a student
in your write-up, you should note the places where controls should hav
e been added if the equipment had been available.
The
Chemicals:
The following Chemicals were used:
A. Potassium
Chlorate KClO3
B. Sucrose
(Table Sugar) C12H22O11
C. Sodium
Chloride (Table Salt)
NaCl
D. Calcium
Chloride CaCl2
E.
Barium Chloride BaCl2
What is the scientific method? What is a
Controlled Experiment?
The Experiment (Record Your Notes):
Step 1: Approximate equal amounts of Chemical A and Chemical B were mixed in an evaporating dish and placed on an asbestos pad.
The crystal mixture was lit with a cigarette lighter and a burn occurred:
Your
Observations:
a. What was the appearance and burn
rate of the fire:
b. What did the residue look like:
Step 2: Approximate
equal amounts of Chemical A
and Chemical B were
mixed in an evaporating dish.
Then Chemical C was added to the mixture
and mixed. The new mixture was placed on another Asbestos Pad.
The new crystal mixture was lit with a cigarette lighter and a burn occurred:
Your
Observations:
c. What was the appearance and burn
rate of the fire:
d. What did the residue look like:
Step 3: Approximate
equal amounts of Chemical A
and Chemical B were
mixed in an evaporating dish.
Then Chemical D was added to the mixture
and mixed. The third mixture was placed on another Asbestos Pad.
The third crystal mixture was lit with a cigarette lighter and a burn occurred:
Your
Observations:
e. What was the appearance and burn
rate of the fire:
f. What did the residue look like:
Step 4: Approximate
equal amounts of Chemical A
and Chemical B were
mixed in an evaporating dish.
Then Chemical E was added to the mixture
and mixed. The fourth mixture
was placed on another Asbestos Pad.
The fourth crystal mixture was lit with a cigarette lighter and a burn occurred:
Your
Observations:
g. What was the appearance and burn
rate of the fire:
h. What did the residue look like:
Conclusions:
What is a controlled experiment?
What was
the purpose of Chemical A?
What was
the purpose of Chemical B?
What
differences occurred during the four burns:
Burn
#1: A + B + fire
Burn
#2: A + B + C + fire
Burn
#3: A + B + D + fire
Burn
#4: A + B + E + fire
What were
the experimental controls?
What were
variables being tested?
What was
another experimental control incorporated into the variable chemicals
when selecting the compounds to test (C; D; E)?
Suggest
better controls that could have been incorporated into the experiment
process of steps: 1, 2, 3, & 4
Now
conclude a hypothesis or several hypotheses that you can make
after recording your observations:
Hypothesis
I:
Hypothesis
II:
Hypothesis
III
Hypothesis
IV:
Now
suggest a step #5 for Experiment #1 with new chemicals:
Step #5:
A + B + F + Flame and using Potassium chloride KCl as
Chemical F
as a fifth chemical to add to the mixture to burn for experiment #1.
From your
research what would you expect to see?
Now
suggest a modification to Experiment #1 by performing an Experiment #2
with a new set of chemicals that would
test your hypothesis:
Burn
#1: A + B + fire
Burn
#2: A + B + C + fire Chemical C:_____________________________
Burn
#3: A + B + D + fire Chemical D:_____________________________
Burn
#4: A + B + E + fire Chemical E:_____________________________
Burn
#5: A + B + F + fire Chemical F:_____________________________
If you are ambitious, you form a team of three and perform Experiment
#1 in the FSCJ Chemistry Lab (D-204)
with the professor incorporating
additional controls. The processed would be videoed and placed on the Internet
. It would also include Experiment #2 and any additional steps or experiment to
add to the process of using the scientific method.
If
You are having trouble understanding what the hypothesis above should be,
maybe you need to Research flame tests for various cations (why not anions?):
Watch the
following Video on Flame test of Cations:
http://www.fccj.us/FlameTests.mp4
The
following are good You-Tubes:
https://www.youtube.com/watch?v=NEUbBAGw14k
https://www.youtube.com/watch?v=1EXr_L7Ojqg