Final answer:
Given the context of the properties and reactions of magnesium, it is probable that Javier forgot to heat the magnesium metal, a necessary step to observe reactions involving this active metal in a lab setting.
Step-by-step explanation:
The question asked pertains to magnesium metal and the context given relates to magnesium's properties and use in construction. Magnesium is described as an active metal that is capable of burning in various forms such as powder and ribbons to produce brilliant light.
This property is what the student should have remembered considering the actions described. When handling experiments with metals like magnesium, heating it with a Bunsen burner may be a necessary step to initiate a reaction, as described in one of the sampled instructions.
Therefore, considering the context provided, it is likely that Javier forgot to heat the magnesium metal, as heating is a common preparation step for reactive metals in a lab setting.