Fact 1: Chemical weathering causes iron in rock to oxidize.

Fact 2: When iron oxidizes, it rusts.

Given the two facts above, answer the question "What causes iron to rust?" with the following options: 
- Chemical energy
 - High pressure
 - harmful substances
 - Greenhouse gasses
 - permineralization
 - Chemical weathering
 - Cold temperatures
 - Direct heat


 

      Chemical weathering   