Final answer:
The temperature at which an igneous mineral crystallizes affects its grain size and stability. High-temperature formation leads to larger, more stable grains resistant to weathering, whereas low-temperature crystallisation results in finer grains that weather more readily.
Step-by-step explanation:
The connection between the temperature at which an igneous mineral crystallises and the rate at which it chemically weathers is rooted in the stability of the mineral's crystal structure. The temperature of formation influences the size and composition of the mineral grains. Minerals that form at higher temperatures tend to have larger crystal grains and stronger bonds due to slower cooling rates, resulting in intrusive or platonic rocks. Conversely, minerals that form at lower temperatures crystallise more quickly, leading to extrusive or volcanic rocks with smaller grains.
Chemical weathering, on the other hand, is affected by the mineral structure and composition. High-temperature minerals with larger crystal grains and stronger bonds are generally more resistant to weathering compared to low-temperature minerals with weaker bonds and smaller grains. Consequently, minerals crystallizing at high temperatures within plutonic rocks tend to weather slower than those in volcanic rocks, which are composed of minerals that crystallized at lower temperatures and have finer grains.
Additionally, rocks with larger grains have a smaller surface area relative to their volume, which decreases the rate of chemical reactions including weathering, compared to rocks with finer grains that have a larger surface area. The enthral of fusion and melting point of a crystalline solid, which relate to the strength of the attractive forces within the crystal, play a part in determining the resilience of a mineral to weathering. Minerals with stronger attractive forces that form at higher temperatures will also melt at higher temperatures and are typically more stable under Earth's surface conditions, resulting in a slower weathering process when exposed to surface conditions.