Question

limestone is a sedimentary rock ( like the one pictured below ) consisting mostly of calcium carbonate (caco₃). which process is most likely to cause a chemical change to limestone? flowing water erodes a limestone riverbed freezing water cracks limestone coastal waves dissolves limestone sediments carbonic acid in seawater forms puddles and caves on limestone

Explanation:

To determine which process causes a chemical change to limestone (composed of \( \text{CaCO}_3 \)), we analyze each option:

• "Flowing water erodes a limestone riverbed": Erosion is a physical process (breaking into smaller pieces, no chemical reaction).
• "Freezing water cracks limestone": Freezing expands water, causing physical cracking (no chemical change).
• "Coastal waves dissolve limestone sediments": Dissolving sediments here is likely physical (e.g., mechanical breakdown or physical dissolution without chemical reaction).
• "Carbonic acid in seawater forms puddles and caves on limestone": Carbonic acid (\( \text{H}_2\text{CO}_3 \)) reacts with \( \text{CaCO}_3 \) (limestone) in a chemical reaction: \( \text{CaCO}_3 + \text{H}_2\text{CO}_3

ightarrow \text{Ca(HCO}_3\text{)}_2 \), which dissolves the limestone, forming caves/puddles (a chemical change).

Answer:

Carbonic acid in seawater forms puddles and caves on limestone