Question

In one experiment, magnesium metal melts. In a second experiment, magnesium metal ignites as it combines with oxygen. Classify the change in each experiment as chemical or physical. Explain your reasoning.

a) The first experiment is a chemical change because melting is a chemical reaction.
b) The second experiment is a physical change because it involves a change in state, not a chemical reaction.
c) Both experiments are physical changes because they do not involve chemical reactions.
d) The first experiment is a physical change, and the second experiment is a chemical change.

Answer 1

Melting magnesium is a physical change, while the ignition of magnesium metal as it reacts with oxygen is a chemical change because it results in the formation of a new substance. Correct option is d)

Step-by-step explanation:

In the experiments described, two distinct processes are involved with magnesium metal. The first involves melting magnesium, which is a physical change because it alters the physical state without changing the chemical composition or molecular structure of magnesium. In the second experiment, where magnesium ignites and combines with oxygen, a chemical change occurs. This is due to the chemical reaction that takes place between magnesium and oxygen, resulting in the formation of magnesium oxide (MgO). The properties of this new compound are different from those of the original elemental magnesium and oxygen, indicating a chemical change.