Why does limestone dissolve in rainwater even without pollution?
ARainwater is naturally slightly acidic because it absorbs carbon dioxide from the air, forming carbonic acid that dissolves calcium carbonate in limestone
BRainwater is pure H2O, which is a natural solvent for all rocks
CLimestone is not actually rock — it is a soft material that dissolves in any liquid
DOnly polluted rain can dissolve limestone
Rainwater absorbs CO2 from the atmosphere, forming weak carbonic acid (H2CO3). This acid reacts with calcium carbonate (CaCO3) in limestone, dissolving it slowly. This natural process created caves, sinkholes, and karst landscapes long before industrial pollution existed.
Question 2 Short Answer
How do mechanical weathering and chemical weathering work together to break down rock faster than either could alone?
Think about your answer, then reveal below.
Model answer: Mechanical weathering cracks rock and breaks it into smaller pieces, increasing the total surface area exposed to water and air. More exposed surface means more area for chemical reactions to occur, speeding up chemical weathering. In turn, chemical weathering weakens the rock along grain boundaries, making it easier for mechanical forces to break it apart further.
They form a positive feedback loop. A solid boulder has limited surface area for chemical attack. Break it into a thousand pieces and you have vastly more surface area — same total rock, but much more exposure to chemicals. This is why weathering accelerates once it begins.
Question 3 True / False
Chemical weathering produces the same minerals as the original rock, just in smaller pieces.
TTrue
FFalse
Answer: False
This describes mechanical weathering, not chemical weathering. Chemical weathering transforms minerals into different substances through chemical reactions. For example, feldspar in granite reacts with water and becomes clay minerals — an entirely different substance with different properties. This is the key distinction between the two types of weathering.