- The water combines with carbon dioxide in the air to form carbonic acid - As the acid is formed, the iron starts to dissolve - Some of the water breaks down into hydrogen and oxygen - The free oxygen and dissolved iron bond together - They form iron oxide, which is rust - What might be the first step of the process?
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Answer: Water comes into contact with something made of iron

- Oxygen moves from the lungs into the bloodstream - Air is pushed through the vocal chords - A person talks - Other air is pushed out of the lungs into the environment. What might be the first step of the process?
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Answer: Air is pulled into the lungs

- Rain picks up carbon dioxide as it falls to earth - The rain falls on the soil over the limestone - The carbon dioxide in the rain washes through the soil - The carbon dioxide turns into acid - The acid in the rain gets to the limestone below the soil - The acid dissolves the limestone - Acid continues to erode the limestone with more rain over time - The eroded limestone sometimes forms caves. What might be the first step of the process?
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Answer:
Limestone is located under the soil