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Assessment
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Show students the Images of Chemical Weathering pictures. Have students answer the following questions related to the pictures:
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Complete this investigation by asking your students the following:
As a result of this investigation, students should be able to state that certain rocks can dissolve when exposed to rainwater, which is slightly acidic. This exposure increases the breakdown of rocks into smaller and smaller pieces.
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The following passage provides more detailed information related to this investigation that you may choose to explain to your students. Chemical Weathering ProcessesChemical weathering is the decomposition of rocks due to chemical reactions occurring between the minerals in rocks and the environment. Following are examples of the chemical weathering processes. WaterWater, and many chemical compounds found in water, is the main agent of chemical weathering. Feldspar, one of the most abundant rock-forming minerals, chemically reacts with water and water-soluble compounds to form clay. AcidsWater contains many weak acids, such as carbonic acid. This weak, but abundant, acid is formed when carbon dioxide gas from the atmosphere mixes with rainwater. Sulfur dioxide and nitrogen gases create other types of acids that act as chemical weathering agents. Some sources of sulfur dioxide are power plants that burn coal; as well as volcanoes and coastal marshes. Sulfur gases react with oxygen and rainwater to form sulfuric acid. Although relatively weak, this acid’s abundance and long term effects produce noticeable damage to vegetation, fabrics, paints and rocks. OxidationOxidation is another kind of chemical weathering that occurs when oxygen combines with another substance and creates compounds called oxides. Rust, for example, is iron oxide. When rocks, particularly those with iron in them, are exposed to air and water, the iron undergoes oxidation, which can weaken the rocks and make them crumble. |
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