Definition

• Chemical weathering is erosion by the weather via chemical processes. Meaning, the process changes existing rock molecules into different molecules. The general reason this could lead to erosion is that harder rock becomes softer or insoluble rock becomes soluble.
  
  

Processes

• More specifically, the processes involved in chemical weathering perform one of the following: expand the rock, increasing stresses; reduce particle size, which increases the surface area on which chemical erosion can occur; create rock that is more mobile; or create more stable (and more compliant) minerals.
  
  

Dissolution

• A specific example of chemical weathering is dissolution, or carbonic acid action. Its acidic action on limestone causes sinkholes and, as acid rain, the dissolving of statues.
  
  

Hydrolysis

• Water turns some minerals into clay. Although more stable, it is also more malleable and conducive to erosion than the original minerals.
  
  

Oxidation

• Oxidation is the combination of oxygen with elements in rock, producing new rock that is usually softer and easier to break. Rust is an example of oxidation.
  
  

Chelation

• Chelation is a fundamental process in soil formation. It involves the absorption of metals by hydrocarbons. Sometimes, this is classified as biological weathering instead of chemical weathering.