CoachA molecule is a group of atoms held tightly together. A molecule is the smallest piece of a substance that is still that substance: a water molecule is the smallest possible amount of water.
Examples
Example 11.7 (Seven molecules)
- the hydrogen molecule: two hydrogen atoms;
- the oxygen molecule, which we breathe: two oxygen atoms;
- the nitrogen molecule, four fifths of the air: two nitrogen atoms;
- the water molecule: two hydrogen atoms and one oxygen atom;
- the carbon dioxide molecule, which we breathe out: one carbon atom and two oxygen atoms;
- the methane molecule, the main part of the natural gas burnt in gas cookers: one carbon atom and four hydrogen atoms;
- the nitrous oxide molecule, an anaesthetic gas: two nitrogen atoms and one oxygen atom.
Example 11.10 (The seven formulas)
The molecules of Example 11.7 have these formulas:
Example 11.13 (Methane in the kitchen)
The natural gas of a gas cooker is mostly methane, . Each of its molecules is one carbon atom with four hydrogen atoms around it. The gas is invisible and has no smell: the smell of “gas” is a substance added on purpose, so that a leak is noticed.