Atoms and molecules
4 marks · NormalThis question is about atoms and molecules.
Copper (Cu) is an element. State what you would have if you kept cutting a piece of copper into smaller pieces until you could not cut it any further and still have copper.
Describe what a molecule is.
Give one example of a substance made of molecules that contain atoms of different elements.
Explain why all molecules are made up of atoms, but not all atoms are part of molecules.
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(a) A copper atom
(b) A molecule is a particle made of two or more atoms chemically bonded together.
(c) Water (H2O) or carbon dioxide (CO2) or ammonia (NH3) or similar
(d) Molecules are made by atoms bonding together, but some atoms can exist alone (as single atoms) and are not part of molecules.
Common mistakes: Confusing atom and molecule; Giving an element as the answer for part (c)
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Marking points
B1 (a) · 1 mark · States that the smallest unit is an atom.
B1 (b) · 1 mark · Describes a molecule as two or more atoms chemically bonded.
B1 (c) · 1 mark · Gives an example: water (H2O), carbon dioxide (CO2), etc.
B1 (d) · 1 mark · Explains that molecules are made of atoms, but not all atoms are bonded into molecules (some are individual atoms).
Worked solution
a) A copper atom.
b) A molecule is made of two or more atoms chemically bonded together.
c) Water (H2O) contains both hydrogen and oxygen atoms bonded as molecules. Other examples: carbon dioxide (CO2), ammonia (NH3).
d) Every molecule always contains atoms, because atoms join together to make molecules. However, some elements exist as single atoms (e.g., helium), and so not all atoms have to be in molecules.