A compound is a molecule made of atoms from different elements. All compounds are molecules, but not all molecules are compounds. Hydrogen gas (H2) is a molecule, but not a compound because it is made of only one element. ... Atoms that share electrons in a chemical bond have covalent bonds.
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Because warm air rises up so it's warmer on the top floor.
Answer:cellular respiration is a process by which cells use oxygen to produce energy from food.
This happens in the mitochondria
