1. Obtain between 0.17 and 0.23 g of magnesium powder or chips.
2. Add the magnesium sample to the crucible.
3. Measure the mass of the crucible, lid, and magnesium to the nearest milligram and record it in Table 3.
4. Return the crucible, with the sample and lid, to the clay triangle over the Bunsen burner.
5. To react all of the metal:
a. Gently heat the sample for 2 to 3 minutes by moving the burner around the bottom of the crucible.
b. Increase the heat and continue heating until the sample starts to glow.
c. Continue moving the burner around the bottom of the crucible.
d. Manage the burning so the magnesium glows for about 3 minutes
e. Continue heating for about 3 more minutes, carefully lifting the lid to observe the contents of the crucible.
f. When the bright glow of the contents of the crucible turns to a pale glow, stop the heating.
g. Allow the crucible to cool to room temperature with the lid in place.
h. Using the tongs to lift the lid, break the crust over the contents of the crucible with a straightened paper clip.
i. Hold the lid with the tongs and mix the contents carefully so that any unreacted metal comes to the surface.
6. Repeat all parts of the step to react all of the metal, until no unreacted metal is visible.
7. When the sample has cooled and no metal is present, use the squeeze bottle to add three drops of deionized water.
8. By wafting the air towards your nose over the crucible, try to identify and describe the smell of ammonia.
9. Heat the crucible and sample again. It takes a considerable amount of time and heat to decompose
a. With the lid slightly open to allow water vapor to escape, begin heating the crucible and sample over a gentle flame for about 3 minutes.
b. Gradually increase the heat, being careful not to let the crucible heat up too fast such that water spatters out.
c. Continue at high heat for about 15 to 20 minutes, carefully lifting the lid to observe the contents of the crucible.
d. When the sample has a pale glow, stop the heating.
e. Allow the crucible to cool to room temperature with the lid in place.
10. After the crucible and sample have cooled, measure and record the mass of the crucible lid, and metal oxide, to the nearest milligram, in Table 2.
11. Reheat the crucible and sample at high heat for 5 minutes. Allow the crucible and sample to cool, then measure and record the mass in Table 2. Repeat this step until you obtain two consecutive readings within 10 mg of each other.
12. Copy the last measurement in Table 2 into Table 3.
13. Dispose of the metal oxide in the appropriate container.
14. Wash the crucible with soap, and then rinse three times with tap water to clean the crucible of magnesium oxide residue.
15. After rinsing three times with tap water, rinse again with deionized water.
Table 2: Mass of the crucible and magnesium oxide, measured to the nearest milligram
Crucible, lid, and MgO after the first heating (g)