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chemical changes - Coggle Diagram
chemical changes
Reactions of metals with oxygen
Many metals react with oxygen to make metal oxides.
For example, magnesium burns rapidly in air:
Magnesium + oyxgen → magnesium oxide
2Mg(s) + O2(g) → 2MgO(s)
The reactions are oxidation reactions
because the metal gains oxygen.
Oxygen can be removed from metal oxides in chemical reactions.
For example:
Copper oxide + carbon → copper + carbon dioxide
2CuO(s) + C(s) → 2Cu(l) + CO2(g)
In this reaction, carbon is oxidised because it gains oxygen. At the same time, copper oxide is reduced because oxygen is removed from it.
Oxidation is the gain of oxygen. Reduction is the loss of oxygen.
reactions of metals
When metals react with other substances, the metal atoms lose electrons to form positive ions.
The reactivity series of metals is a chart showing metals in order of decreasing reactivity.
In general, the more reactive a metal is:
the more vigorous its reactions are
the more easily it loses electrons in reactions to form positive ions (cations)
reactions of metals with water
When a metal reacts with water, a metal hydroxide and hydrogen are formed.
For example, sodium reacts rapidly with cold water:
Sodium + water → sodium hydroxide + hydrogen
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
In general, the more reactive the metal, the more rapid the reaction is.
Reactions of metals with dilute acids
When a metal reacts with a dilute acid, a salt and hydrogen are formed.
For example, magnesium reacts rapidly with dilute hydrochloric acid:
Magnesium + hydrochloric acid → magnesium chloride + hydrogen
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)