2. this is a form of ground water pollution where heavier chemicals fall back to the ground and coat the trees and leaves of plants.
-acid rain
-deposition
-global warming
-greenhouse effect

The right answer is Deposition.

This is the case, for example, with chlorinated solvents.

Chlorinated solvents, or chlorinated aliphatic hydrocarbons, are used as solvents for the cleaning as well as for the extraction and the separation of certain products, they are also used as refrigerants (chlorofluorocarbon or CFC). They are widespread. Their presence in landfills of all types constitutes a risk of groundwater pollution because they are not retained by the clays. After percolation into the ground, groundwater near urban or industrial areas (industrial discharges) can be contaminated by these highly volatile pollutants. They are not degradable and tend to settle in the lower part of the water table.

its temperature is increasing. this causes molecular vibrations to increase.

it provides an alternative energy pathway for the reaction to proceed.

a catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction.

catalysts increase the rate of reaction without being used up. they do this by lowering the activation energy needed. with a catalyst, more collisions result in a reaction, so the rate of reaction increases. different reactions need different catalysts.

a catalyst works by providing an alternative reaction pathway to the reaction product. the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.