Which statement best distinguishes physical and chemical weathering in soils, and which can release nutrients into waterways?

Which statement best distinguishes physical and chemical weathering in soils, and which can release nutrients into waterways?

• A. Physical weathering breaks rocks into smaller pieces; chemical weathering changes chemical composition releasing nutrients.
• B. Chemical weathering breaks rocks into smaller pieces; physical weathering changes chemical composition releasing nutrients.
• C. Only chemical weathering releases nutrients; physical weathering does not.
• D. Weathering does not release nutrients into waterways.

Answer: (A)

The key idea is that physical weathering and chemical weathering differ in whether the rock’s chemical makeup changes. Physical weathering is mechanical: rocks are broken into smaller pieces without changing their minerals or chemistry. Chemical weathering changes the minerals themselves through reactions with water, acids, or oxygen, producing new minerals or dissolving ions. When minerals dissolve, they release nutrients like calcium, potassium, magnesium, and phosphate into water, which can flow into waterways. So the best statement is the one that says physical weathering breaks rocks into smaller pieces and chemical weathering changes chemical composition releasing nutrients. The other options misstate the processes or overstate nutrient release, and one misleads by claiming no nutrients are released at all.

The key idea is that physical weathering and chemical weathering differ in whether the rock’s chemical makeup changes. Physical weathering is mechanical: rocks are broken into smaller pieces without changing their minerals or chemistry. Chemical weathering changes the minerals themselves through reactions with water, acids, or oxygen, producing new minerals or dissolving ions. When minerals dissolve, they release nutrients like calcium, potassium, magnesium, and phosphate into water, which can flow into waterways.

So the best statement is the one that says physical weathering breaks rocks into smaller pieces and chemical weathering changes chemical composition releasing nutrients. The other options misstate the processes or overstate nutrient release, and one misleads by claiming no nutrients are released at all.