ICSE Class 9 Answered

Various processes that are involved in chemical weathering are:

Solution: When the minerals present in rocks get dissolved in water, it is known as solution. The rate at which the solution of rocks take place is subject to the chemical composition and the structure of rocks. For example, salt present in rocks is more soluble in water.

Carbonation: Many rocks contain constituents which have carbon dioxide present in them. When it comes in contact with water, an acidic affect on rocks is produced. Many rocks like marble and limestone get dissolved in water. Rainwater converts carbonate into calcium bicarbonate which is soluble and hence gets dissolved in water.

Oxidation: When minerals present in rocks react with oxygen present in the atmosphere, it results in oxidation. Rain water also contains atmospheric oxygen. When it comes into contact with the iron compounds in the rocks, iron begins to rust. This may also change the colour of the rocks to red, brown or yellow.

Hydration: When the minerals present in the rocks expand on coming into contact with rainwater, the process of hydration takes place. The minerals in this process become heavy and begin to breakdown. In such a process, rocks like feldspar get converted into kaolin.