CHEM
LAB
Identification of Metals:
Flame Tests
Introduction
When elements are heated to high temperatures, some of their electrons are excited
to higher energy levels. These excited electrons can then fall back to lower energy levels,
releasing the excess energy in packets of light called photons, or quanta. The color of
light emitted, depends on its energy. Blue light is more energetic than red light. When
heated, each element emits a characteristic pattern of light energies which is useful for
identifying the element. The characteristic colors of light produced when substances
are heated in the flame of a Bunsen burner are the basis of flame tests for several
elements.
In this experiment you will perform flame tests for several metallic elements. You will
also attempt to identify metallic elements by the color of their flames.
Objectives
1. To observe the colors emitted by various metal ions.
2. To evaluate flame tests as a method of detection of metal ions.
Equipment
safety goggles
platinum wire
50 mL beaker
small test tubes
test tube rack
scoopula
cobalt glass
bunsen burner
Materials
6M HCl, hydrochloric acid
sodium nitrate, NaNO3
potassium nitrate, KNO3
calcium nitrate, Ca(NO3)2
strontium nitrate, Sr(NO3)2
lithium nitrate, LiNO3
copper (II) nitrate, Cu(NO3)2
barium nitrate, Ba(NO3)2
Procedure
1.
2.
3.
4.
5.
6.
7.
8.
Obtain a small amount of a salt containing the metal ion to be tested
Place this sample onto a clean watch glass
Add enough distilled water to dissolve the salt, 10-15 drops.
Obtain a clean wire loop. Follow the illustration below to clean the wire
Dip the wire into the salt solution, then place the tip of the wire into the flame
Be careful NOT to heat the glass holding the wire…it will break!
Record observations in the data chart
Clean the wire as before and repeat the procedure with each salt sample
WEAR YOUR GOGGLES AT ALL TIMES
DURING THIS LAB!
Name: ________________________________________ Period: _______ Date: ___________________
Flame Test Lab – Data Sheet
Observations
(Flame Color)
Metal Ion
Sodium, Na
Unknown I.D.
+
WITH COBALT GLASS:
+
Potassium, K
WITH COBALT GLASS:
Calcium, Ca
Barium, Ba
+2
+2
Strontium, Sr
+2
+
Lithium, Li
Copper, Cu
+2
Results and Conclusions
1. List the elements that gave the most easily identified colors. Which elements are least easily
identified?
2. Which element gives the most intense color?
3. Would flame tests be a useful method for detecting metal ions in a mixture of salts? Why or why
not?
4. The energy of colored light increases in the order red, yellow, green, blue, and violet. List the
metallic elements used in this lab in order of increasing energy of the light emitted by their flame
tests.
5. What is the purpose of using the cobalt glass in the identification of sodium and potassium?