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Burning metals in air and in oxygen.

Answer Text:
Burning metals in air and in oxygen.
Requirements:
- Metals; deflagrating spoon; gas jar; source of heat;
Diagram of apparatus;

Procedure:
- A piece of sodium is warmed on a deflagrating spoon until it begins to burn;
- It is then lowered into a gas jar of air as shown above;
- The flame colour is noted;
- The gas jar is allowed to cool; some water added to the product(s) in the gas jar and shook well;
- Any gases produced are tested by smell and also with litmus papers;
- The experiment is then repeated with pure oxygen;
- The whole procedure is repeated with other metals;
Observations;
- When substances burn in oxygen they form only oxides; as opposed to burning substances in air where some react with both air and nitrogen;
- Different substances produce different flame colours;
- Many metals burn in air and in oxygen at different speeds; with more reactive metals burning more vigorously than the less reactive metals;
- Burning is faster in oxygen than in air;
Reason:
- Oxygen is pure but in air there are other constituents such as nitrogen, carbon (IV) oxide and noble gases which slow down the burning;
- In air products are generally oxides and in some few cases (magnesium and sodium) nitrides as well;
- Metals that tend to be more reactive are the ones that react with both oxygen and nitrogen;
- In oxygen products are strictly oxides;
- Some of the products are soluble in water while others are not.
Sample equations:
Magnesium: With oxygen:
Magnesium + oxygen → Magnesium oxide;
#Mg(s) + O_2(g) → MgO(s)#;
With nitrogen:
Magnesium + Nitrogen →Magnesium nitride;
#3Mg(s) + N_2(g) → Mg_3N_2(s)#;
Sodium:
With oxygen:
Sodium + oxygen → Sodium oxide;
#4Na(s) + O_2(g) → 2Na_2O(s)#;
With nitrogen:
Sodium + Nitrogen →Magnesium nitride;
#6Na(s) + N_2(g) → 2Na_3N(s)#;