Arnoldi

Chem Com

Unit Two Section A

Flame Test Laboratory:

Group Characteristics and the Periodic Table

When we study the periodic table we often see that characteristics can be shared among the elements of a particular group. Noble Gases, for example, are extremely non-reactive. We also saw that Alkali Metals have characteristic flame colors. So do Group 2 elements (and a few transition elements). These elements can then be identified in compounds by the color produced in a flame as atoms vaporize, become excited, and return to lower energy states.

MATERIALS

Part One Computer Video

Magnesium: http://www.youtube.com/watch?v=V2TimLxskZw

Calcium: http://www.youtube.com/watch?v=yXjVjuFBVrk

Strontium: http://www.youtube.com/watch?v=Kvxg95xY5vk

Alkali Metals: http://www.youtube.com/watch?v=m55kgyApYrY

Part Two Striker

Tester

Solutions (Ba, Ca, Cu, Li, K, Na, Sr)

6 M HCl


PROCEDURE

Part One

Observe the videos regarding activity of the metals in groups one and two.

Record your observations here. Be sure to include a comparison of the Alkali Metals to each other, the Alkaline Earth Metals to each other, and the Alkali Metal Group to the Alkaline Earth Metals group.


Part Two

1. Cleanse your testing wire by dipping it into the HCl solution, and heating it in the flame. When the flame color no longer changes, the wire is clean. TWO NOTES: 6 M HCl is very strong. Avoid contact with your skin and do not inhale its fumes. Also, if you hold the wire in the flame for an excessive period of time, the wire will begin to glow, and the flame will change color – this does not indicate a dirty wire.

2. Dip your wire into one of the known solutions. Place the wire onto the edge of the flame as shown by your teacher. Observe the color created. Explain the color thoroughly in your date table.

3. Clean the wire as explained in step one.

4. Repeat the color test and cleaning for each of the known solutions.

5. Repeat the color test and cleaning for four unknown solutions. Keep testing until you are sure you can correctly identify the unknown! You may need to go back and retest a known to clarify your thinking!

Fill in the following table.

Element / Color
Barium
Calcium
Copper
Lithium
Potassium
Sodium
Strontium
Unknown ___
Unknown ___
Unknown ___
Unknown ___


LEFT BLANK ON PURPOSE


Arnoldi

Chem Com

Unit Two Section A

Flame Test Laboratory Write-up

DATA:

Part One Summarize what you learned about the activity of column one and column two metals.

Part Two

Fill in the following table.

Element / Color
Barium
Calcium
Copper
Lithium
Potassium
Sodium
Strontium
Unknown ___
Unknown ___
Unknown ___
Unknown ___

ANALYSIS

1. Theory and Discussion

What specific trend / group characteristic was demonstrated in each part of the lab?

Part One

Part Two

Explain why a distinct flame color for different elements could be a useful property.

2. Complete each of the following:

a. As you go down the Periodic Table, the activity of the Alkali Metals…

b. As you go down the Periodic Table, the activity of the Alkaline Earth Metals…

c. In general, Alkali Metals are ______active than Alkaline Earth Metals. (more or less)

3. Identify TWO of your FOUR unknowns.

Unknown ______

Unknown ______

4. Error Analysis

You needed to identify unknown elements based upon their flame color. What might have caused you to incorrectly identify them? There are several possible factors.