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:

1. Mega Lab - Flame Test - Li, Na, K, Ca, Sr, Ba, Cu

https://www.youtube.com/watch?v=NEUbBAGw14k

2. Qualitative analysis cations: the flame test
https://www.youtube.com/watch?v=LYSblvmOmfg

3. Flame Tests of Metal Ions, With Labels

https://www.youtube.com/watch?v=1EXr_L7Ojqg