T4+notes

T4+notes - Physical and Chemical Weathering(Topic 4 Rock...

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Physical and Chemical Weathering (Topic 4) Rock weathering can be divided into two sets of processes: 1. Physical weathering (disintegration) - the original rock disintegrates to smaller-sized material with no appreciable change in chemical or mineralogical composition. - physical weathering increases the surface area exposed for chemical weathering. 2. Chemical weathering (decomposition) - the chemical and mineralogical composition of the original rock and minerals is changed. Agents of Physical Weathering 1. Temperature a. Heating and cooling exfoliation - separation of concentric shells or layers of rock b. Ice and hydrofracturing by freezing - ice expands 9% in volume relative to liquid H 2 O 2. Water, ice and wind - abrasion and grinding 3. Plants and animals 4. Pressure release or unloading Chemical Weathering 1. Solution - dissolving a substance in water (water is the solvent) Example: table salt NaCl ⎯→ Na + + Cl - solid ⎯→ liquid 2. Hydration - the addition of water molecules to a mineral CaSO 4 + 2H 2 O ⎯→ CaSO 4 · 2H 2 O plaster of Paris gypsum 3. Hydrolysis - splitting of water followed by reaction of H
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T4+notes - Physical and Chemical Weathering(Topic 4 Rock...

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