Atoms and molecules
3 marks · EasyThe table shows three simple substances. Use the information to answer the questions.
| Substance | Atoms present |
|---|---|
| Hydrogen | H₂ |
| Nitrogen | N₂ |
| Water | H₂O |
Which of these substances are molecules made from only one type of atom?
How many atoms are present in one molecule of water?
State why water is classified as a molecule.
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(a) Hydrogen (H₂) and nitrogen (N₂)
(b) 3
(c) It is made from two or more atoms chemically bonded together.
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Marking points
B1 (a) · 1 mark · Identifies hydrogen (H₂) and nitrogen (N₂) as molecules of one element.
B1 (b) · 1 mark · Gives correct count: 3 atoms in one H₂O molecule.
B1 (c) · 1 mark · Correct reason: water is a molecule because its atoms are chemically bonded.
Worked solution
a) Hydrogen (H₂) and nitrogen (N₂) are made from only one type of atom. b) H₂O contains 2 hydrogen + 1 oxygen = 3 atoms. c) Water is a molecule because it contains atoms that are chemically bonded together.