Question

how does chemical weathering occur?
plants, lichens, and mosses accelerating breakdown
due to physical factors such as freezing and thawing
by chemically breaking down rocks by water and gases

Explanation:

Chemical weathering occurs when rocks are broken down through chemical reactions. Water (e.g., acidic rainwater) and gases (like carbon dioxide) react with minerals in rocks. For example, carbon dioxide dissolves in water to form carbonic acid, which can react with calcium - containing minerals in rocks. Physical factors like freezing and thawing are related to physical weathering. Plants, lichens, and mosses accelerating breakdown is more related to biological weathering (a sub - type of physical or chemical in some cases, but not the direct mechanism of chemical weathering as described here).

Answer:

by chemically breaking down rocks by water and gases