Question

A teacher holds a strip of gray magnesium metal in a flame. Which statement correctly describes the change?

a) Oxygen and magnesium form a mixture with the same properties as the original materials
b) Oxygen and magnesium form a solution with different properties from the original materials
c) Oxygen and magnesium form a compound with the same properties as the original materials.
d) Oxygen and magnesium form a new substance with different properties from the originals.

Answer 1

Magnesium and oxygen combine in a chemical reaction when magnesium is heated in a flame, forming a new substance, magnesium oxide, with different properties than the original elements.

Step-by-step explanation:

When a strip of gray magnesium metal is held in a flame, oxygen and magnesium combine in a chemical reaction to form a new substance, magnesium oxide (MgO). This process is called oxidation, where magnesium is oxidized. The properties of magnesium oxide are different from those of the original magnesium metal and oxygen gas. Magnesium oxide is a crumbly white powder, distinct from the shiny metallic magnesium and the invisible oxygen gas.

The balanced chemical equation for this reaction is:

2Mg (s) + O₂(g) → 2MgO (s)

This reaction is an example of a combination reaction where magnesium is combined with oxygen to form an oxide, apply the principle of the Conservation of Mass, which states that matter is neither created nor destroyed during a chemical reaction. Therefore, the mass of the magnesium oxide produced will be equal to the sum of the masses of the magnesium and oxygen that reacted.