Weathering may be caused by the action of water, air, chemicals, plants, or animals. Chemical weathering involves chemical changes in the minerals of the rock, or on the surface of the rock, that make the rock change its shape or color. Carbon dioxide, oxygen, water, and acids may all cause chemical weathering.Mechanical weathering is the process of breaking a large rock into smaller pieces without changing the minerals in the rock. Mechanical weathering may be caused by frost, ice, plant roots, running water, or heat from the sun.eathering may be caused by the action of water, air, chemicals, plants, or animals. Chemical weathering involves chemical changes in the minerals of the rock, or on the surface of the rock, that make the rock change its shape or color. Carbon dioxide, oxygen, water, and acids may all cause chemical weathering.