Summaries after sample
, Mixtures of elements and compounds
Elements (cont.)
Elements and compounds are
Atoms can form molecules
often mixed together
of compounds
• Air is a mixture of elements (nitrogen and
oxygen) and compounds (water vapour and • Different atoms can join to form molecules -
sulphur dioxide). molecules of compounds.
•
• These substances are mixtures - they aren't T1: Atoms
chemically bonded and their amounts can vary.
• (B)
Compounds
•
Different methods are used to
Compounds consist of
•
Sample
separate mixtures and compounds
Mixtures are separated through physical
methods - hand separation, separation using
magnets, sieving, decanting, filtration and
distillation.
Compounds are formed by
chemical reactions
atoms of different elements
•
•
When 2 or more different atoms bonded in
a fixed ratio, molecules of compounds form.
Molecules of compounds can break down
Summaries after sample
• Compounds are separated through chemical into its individual elements.
methods - require energy (heat or • Atoms are brought closer in a •
electrolysis). chemical reaction - the atoms have •
• bonded. Atoms bond in a fixed ratio
• • Breaking a bond requires sufficient
energy to overcome the force • Oxygen gas (O2) is a diatomic molecule and has a 1:1
between the atoms. oxygen-to-oxygen ratio.
• Water (H2O) has a 2:1 hydrogen-to-oxygen ratio.
Compounds can be broken down •
• • Carbon dioxide (CO2) has a 1:2 carbon-to-oxygen ratio.
in a decomposition reaction •
•
• With enough energy, the atoms in a Chemical bonds hold atoms together
compound can be separated.
• They can break down into other compounds • Forces of attraction between water molecules
or their original elements - decomposition and atoms in water molecules cause these
reaction. atoms to stick together.
• The energy can be heat or electrical energy. • Forces hold the atoms of a compound together -
• chemical bond.
• •
•
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GR8 NS Mind Map
, Sample
Summaries after sample