Fireworks and Mystery Metal activity

Posted by Unknown |

WHAT CAUSES THE BRIGHT COLORS IN FIREWORKS?

Mystery Metal and flame test

Flame tests are useful in lab. situations when it is necessary to identify a compound that is an unknown. This happens frequently when labels fall off of containers. Many fireworks get their colour because salts burn brightly. Copper salts give fireworks green colour and lithium aand strontium produce red colours.

Material

Fume cupboard; Bunsen burner and bench protection sheet

2 crucibles, containing unknown, labelled A & B

5 crucibles, each containing a different metal compounds,
flame test wires with cork holders
2M hydrochloric acid (corrosive)
calcium chloride (irritant)
copper chloride (toxic)
strontium chloride (irritant)
sodium chloride
potassium chloride

WEAR SAFETY GLASSES ALL THE TIME; TURN ON EXHAUST FANS

Procedure (teacher's demo for Yr4 students)

Light the Bunsen burner. Adjust it to get a roaring flame.

Dip the flame test wire into the concentrated acid, then hold it in the hottest part of the flame. Repeat the process until there is little or no colour from the test wire in the flame. Let it cool. You may have to repeat this step several times especially towards the end of the experiment.

Take one of the crucibles containing a known metal compound. Now pick up the flame test wire. Dip the tip of the wire into a little concentrated hydrochloric acid. Then touch the compound in the crucible with the tip so that a tiny bit of the powder sticks to it.

Hold the wire in the flame of the Bunsen burner so that the powdered solid is in the edge of the flame. You should see a coloured flame. Write down the colour in the table below.

Now repeat instructions 2 to 4 with the other four compounds. Write down the flame colour for each metal in the table.

OBSERVE & RECORD RESULTS

Name of Metal Salt Used	Colour of Flame
Sodium Chloride
Potassium Chloride
Calcium Chloride
Copper Chloride (or sulphate)
Strontium Chloride

Now you are ready to help Sherlock Holmes identify the substances. Take one of the unknown substances, then do the flame test on it and see if you can tell which metal is in it from the colour of the flame.

Test of the unknown