After physical weathering, what generally does not change in rock minerals?

Correct answer: Chemical composition

The direct answer is A, chemical composition. Physical weathering breaks a rock into smaller pieces without normally changing the minerals into new chemical substances. The reasoning is: a large rock is cracked, split, expanded, contracted, or rubbed; the pieces become smaller; the total exposed surface may increase; however, the minerals generally remain chemically the same. Option A is correct because chemical composition is normally unchanged in physical weathering. Option B, size of pieces, is wrong because physical weathering commonly makes pieces smaller. Option C, number of particles, is wrong because one rock can break into many more pieces. Option D, surface area, is wrong because smaller fragments usually create a greater total surface area, although the exact increase depends on how the rock breaks. The word generally matters: physical weathering does not absolutely prevent every chemical change in nature, but its defining effect is mechanical breaking. Memory cue: physical weathering changes form and size, not usually the chemical identity.