Micro Experiment: Flame Tests

Introduction

Fireworks are always crowd favorites. Have you wondered where those fantastic colors come from? In this lab, you will be exploring the phenomena of colors produced by burning inorganic salts.

Safety

Open flame is involved in the lab. Proper precautions have to be taken.

Micro Apparatus:

Burner and tubing

Wood splint soaked in water

Pre- Lab: Write proper chemical formulas for each of the 8 chemicals to be used in lab.

Each chemical is an ionic compound.

Use links on wires page under the lab link.

Answer the following items:

  1. What is an ion?
  2. What are the two ways in which an atom may ionize?
  3. What are the names of the two types of ions?
  4. Ions are attracted to each other because
  5. When ions form compounds, the charge is what?

Micro Materials (in small bottles)

strontium nitrate

barium nitrate

calcium nitrate

lithium nitrate

lead(II) nitrate

sodium nitrate

copper(II) nitrate

distilled water

NOTE: The salts may be nitrates or/and chlorides. Check bottle for identification.

Micro Procedure

  1. Record all observations in your Data Table as you complete each procedure.
  1. Turn on Bunsen burner. The flame should be blue and free of any yellowish color.
  1. Use a clean spatula to transfer several crystals of the barium nitratesalt to a clean watch glass. Observe and record in the data table. Note: use the KimWipe to clean the spatula or watch glass if necessary. Few crystals of the salt are sufficient for the test. Try to minimize the usage of chemicals.
  1. Dip the wooden splint pre-soaked in distilled water into the barium nitrate crystals. Hold it very briefly in the flame and record your observations. Note: do not let the splint catch on fire.
  1. Dispose the wooden splint in the solid waste container.
  1. Repeat steps (3-5) using in turn the compounds of lithium nitrate, strontium nitrate, copper(II) nitrate, sodium nitrate, calcium nitrate, lead nitrate, and potassium nitrate. Record all results in the Data Table.
  1. Repeat the flame test on copper(II) nitrate, calcium nitrate and lithium nitrate. Record all results in the Data Table.

Data Table

Flame Tests

Compound / Metallic Ion Present (cation) / Observations Prior to the Test / Color of Flame

Analysis and conclusions

  1. What are ionic compounds?
  2. What is the formula unit for each of the ionic compound tested?
  3. What is common among those ionic compounds?
  4. What is different among those ionic compounds?
  5. Was the color for selected ionic compounds (salts) reproducible? Check within the same lab group and among different groups within the same class.
  6. Why the wooden splint has to be soaked with water and only held over the flame briefly?
  7. Based on the observations, where do those lights come from?
  8. Can the flame test being used for the purpose of identifying ions?