Final answer:
Gases like sulfur dioxide mix with atmospheric water vapor to form sulfuric acid, which falls to Earth as acid rain, damaging the environment and man-made structures.
Step-by-step explanation:
When gases like sulfur dioxide (SO2) mix with water vapor in the Earth's atmosphere, they can form acidic compounds. Sulfur dioxide primarily comes from the burning of fossil fuels like coal and from volcanic eruptions. When sulfur dioxide reacts with water, it forms sulfurous acid (H2SO3), which can further oxidize to become sulfuric acid (H2SO4). This process contributes to the phenomenon of acid rain. Acid rain has the potential to damage both the natural environment, by lowering the pH of lakes and killing aquatic life, and human-made structures, as seen in the chemical degradation of monuments like the Lincoln Memorial.