Question

Old photographic flashbulbs burn magnesium metal in a reaction that causes a flash of brilliant white light. A photographer would need to take care not to suffer burned fingers when trying to replace the hot bulb. What best identifies the energy transformation that occurs in the flashbulb?

A. Chemical energy to electromagnetic energy and thermal energy.
B. Electromagnetic energy to chemical energy and thermal energy.
C. Chemical energy to electromagnetic energy.
D. thermal energy to chemical energy

Answer 1

Answer is: A. Chemical energy to electromagnetic energy and thermal energy.

Balanced chemical reaction: 2Mg(s) + O₂(g) → 2MgO(s) + energy.

This is chemical change (chemical reaction), because new substance (magnesium oxide MgO) is formed, the atoms are rearranged and the reaction is followed by an energy change (exothermic reaction because energy is released).

Chemical changes (chemical synthesis) is when a substance combines with another (in this example magnesium and oxygen) to form a new substance.