Questions

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Bookkeeper is the only English word that has three consecutive double letters.

True, the carbon in the ocean originates from the atmosphere. The oceanic surface water absorbs the carbon dioxide gas from the atmosphere and dissolves in it.

In chemistry rusting is called as oxidation. Oxidation is a chemical process where metal gains oxygen and become oxide. In rusting the Iron ore make a chemical reaction with the oxygen in the presence of water and environmental or atmospheric moisture to produce an Iron oxide. Iron oxide is otherwise called as rust.

The rusting of iron is a chemical change because it is two substances reacting together to make a new substance. 

Rusting would only be a physical change if iron molecules remained pure iron throughout the process.