Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

[Q]: Question: What substances dissociate into ions when dissolved in water? Answer: ionic
[A]: Ionic substances dissociate into ions when they dissolve in water, but most molecular substances do not.

[Q]: Question: What are the two main types of air pollutants? Answer: primary and secondary
[A]: There are two main types of air pollutants: primary and secondary. Most air pollutants come from burning fossil fuels. Some come from burning forests. Some are due to the evaporation of chemicals.

[Q]: Question: Carbonic acid decomposes easily at room temperature into carbon dioxide and what else? Answer: water
[A]:
Some unstable acids decompose to produce nonmetal oxides and water. Carbonic acid decomposes easily at room temperature into carbon dioxide and water.