Chemical Changes Key Points

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  • Created by: aster16
  • Created on: 10-08-20 14:26

Reactivity of Metals

OILRIG- Oxidation Is Loss and Reduction is Gain ( of oxygen)- Oxidation and reduction always occur together 

The Reactivity of Metals- when metals react their atoms lose electrons to form positive metal ions. Some metals lose electrons more easily than others, the easier the metal loses an electron the more reactive it is.

Metals react with acids to produce metal salts and hydrogen 

In a displacement reaction, a more reactive metal will displace a less reactive metal from a solution of its salt 

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The pH Scale and Salts

When substances dissolve in water they dissociate into their individual ions

Indicators are dyes that change colour depending on whether they are acidic or alkaline solutions

- Litmus changes colour from red to blue. Universal indicator is a mixture of dyes that shows a range of colours to indicate how acidic/alkaline a substance is.

soluble bases are called alkalis, acids are neutralised by bases

soluble salts can be made by reacting acids with insoluble bases such as metal oxides, metal hydroxides and metal carbonates. Strong acids such as hydrochloric acid, nitric acid and sulfuric acid are completely ionised in water. Weak acids such as ethanoic acid, citric acid and carbonic acid are only partially ionised in water.

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Electrolysis

Electrolysis is the process of decomposing (breaking down) an ionic substance, called an electrolyte, into simpler substances using electricity. The chemical reaction of electrolysis occurs when an electric current is passed through a solution containing ions (ions are charged atoms, they have more or less electrons than protons which causes an imbalance, the overall charge can be negative or positive).

For the electrolyte to conduct electricity, it must be an ionic compound or in a molten/aqueous state

 

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Process of Electrolysis

  1. The ionic substance is heated until it melts.
  2. The ions are able to move freely after the ionic substance is melted.
  3. The power supply is connected and the electrodes are charged.
  4. The ions move to the oppositely charged electrode.
  5. The electrodes give/take electrons from the ions which makes the ions neutral.
  6. The ions become atoms (because they are neutral) and are deposited onto the electrode. 
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