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The change in color of sandstone from brown to rusty red due to exposure to water and air is an example of chemical weathering. Here's why:
1. **Chemical weathering:** This process involves the breakdown of rocks through chemical reactions that alter their composition. In this case, the minerals in the sandstone are reacting with the water and oxygen in the air, leading to a change in color from brown to rusty red. This change is caused by the oxidation of iron minerals in the sandstone.
2. **Mechanical weathering:** On the other hand, mechanical weathering involves the physical breakdown of rocks into smaller pieces without changing their chemical composition. Examples of mechanical weathering include processes like frost wedging, root wedging, and abrasion.
In conclusion, the color change of the sandstone is a result of chemical reactions occurring between the minerals in the rock and environmental factors like water and air, making it an example of chemical weathering.
