Describe the factors that control the rate of chemical weathering and those that control the rate of physical weathering

The rate of chemical weathering is controlled by such things as the temperature, the amount of rainfall and the surface area of the minerals which constitute the rocks. Rocks with a finer grain size have more surface area than coarse-grained rocks so are more susceptible to chemical weathering, like a volcanic rock compared to a granite, say. With higher temperatures and greater rainfall, chemical reactions in the rocks are facilitated and this is why, for example argillic (clay alteration) alteration is so well developed in the tropics (in El Salvador for example and also why the lateritic soils develop in countries like Indonesia and can contain economic amounts of nickel for exampl). A factor which controls the rate of physical weathering could be the development of glaciers which transport rocks in their bed, which shapes these boulders and also scores the rocky surfaces these scrape over as the glacier moves. Alternate freezing and thawing in the spring time in the northern hemisphere can speed up the breakdown of the rock by cracking it or opening up pre-existing joints and faults.

and also the surface area of the minerals being attacked.