This page contains the detailed and easy notes for GCSE Edexcel Chemistry Chemical Changes for revision and understanding Chemical Changes .

Banner 1

GCSE Edexcel Chemical Changes Complete Revision Summary

CHEMICAL CHANGES

Banner 2

 CHEMICAL CHANGES

• Reactivity of Metals
• Reactivity Series
• Extraction of Metals
• Acids and Bases
• Neutralization
• Making Soluble Salts
• Making Insoluble Salts
• Titrations
• Electrolysis
• Electrolysis of molten compounds
• Electrolysis of aqueous solutions
• Electrolysis of Aluminium

REACTIVITY SERIES

Metal + Dilute Acids = Salt + Hydrogen Metal + Water = Metal Hydroxide + Hydrogen

DISPLACEMENT REACTION

More reactive metal will displace the less reactive metal from its salt solution. Magnesium(More reactive metal)  + Zinc sulphate (Less reactive salt )  = Magnesium sulphate (More reactive metal displaces the less reactive) + Zinc Lead + Magnesium Sulphate                =                No reaction (Less reactive metal cannot displace the more reactive metal) Banner 3

METAL EXTRACTION

MINERALS Minerals are the rocks which contains metal. ROCKS Rocks are the minerals from which metals can be extracted profitably. REDUCTION OF METAL OXIDES Since most of the metals exist in the form of oxides, they can be extracted by reducing the ore. By HYDROGEN All the metal below hydrogen can be reduced by hydrogen BY CARBON All metal below carbon can be extracted by carbon BY ELECTROLYSIS Metals that are above carbon and hydrogen will be extract by Electrolysis Banner 4

_CHEMICAL CHANGES

Download

Restricted download

×

To download this file, please fill in this form
• Email
• Name
• Job title
• Company
• Check In
• GET YOUR FILE

OXIDATION AND REDUCTION

Oxidation

• Gain of Oxygen
• Loss Of hydrogen
• Loss of electrons

C + O₂                  CO₂ CH₄ + O₂                  CO₂ + H₂O 2Cl^–                   Cl₂ + 2e Reduction

• Loss of Oxygen
• Gain of Hydrogen
• Gain of electrons

CuO + Zn                  Cu + ZnO H₂S + Cl₂                  2HCl + S Na⁺ + e^–                   Na Copper Oxide + Hydrogen                     Copper + Water CuO + H₂                  Cu + H₂O Zinc Oxide + Carbon Zinc + Carbon Dioxide 2ZnO + C                  2Zn + CO₂

ACIDS BASES and ALKALI

The substance which have pH less than 7. Banner 5 Strong Acids

• They completely dissociated in water to release H+ ions
• Hydrochloric Acid HCl
• Sulphuric Acid H₂SO₄
• Nitric Acid HNO₃
• Phosphoric Acid H₃PO₄
• HCl H⁺ + Cl^–
• pH = 1-3

Weak Acids

• They are partially dissociated in water to release H+ ions
• Vinegar: Ethanoic Acid
• Lemon: Citric Acid
• CH₃COOH CH₃COO^– + H⁺
• pH = 5-7

The substance which have pH greater than 7.

• Metal Oxides, Metal Hydroxides, Metal Carbonates
• Lithium Oxide, Lithium Carbonate, Lithium Hydroxide
• Alkali are the soluble bases. So bases that can dissolve in water.
• Alkali metal hydoxide
• They release hydroxide ions when dissolved in water.

INDICATORS

Acids	Bases
Taste Sour	Taste Bitter
Not soapy	Feels soapy
have pungent small	do not have a pungent smell
When ionize give hydrogen ions	Give hydroxide ions
Turns blue litmus red	Turns red litmus Blue
eg Hydrochloric Acid	eg Sodium Hydroxide
Sulphuric Acid

NEUTRALIZATION REACTION

Acid + Base                  Salt + Water                          Metal                  Acid Hydrochloric Acid -makes chloride salt Sulphuric Acid – makes sulphate salt Nitric Acid – makes nitrate salt Eg Sodium Chloride + Water                  Sodium Hydroxide + Hydrochloric Acid NaOH + HCl                  NaCl + H₂O Potassium Oxide + Sulphuric Acid                            Potassium Sulphate + Water K₂O + H₂SO₄                   K₂SO₄ + H₂O Magnesium Hydroxide + Nitric Acid                   Magnesium Nitrate + Water Mg(OH)₂ +2HNO₃                   Mg(NO₃)₂ +2H₂O Calcium Carbonate + Sulphuric Acid              Calcium Sulphate + Carbonate + Water CaCO₃ + H₂SO₄                          CaSO₄ + H₂O + CO₂ REACTIONS OF ACIDS

• Metal + Acid = Salt + Hydrogen
• Metal Oxide + Acid = Salt + Water
• Metal Hydroxide + Acid = Salt + Water
• Metal Carbonate + Acid = Salt Water + CO₂

2Na + 2HCl                  2NaCl +H₂ Making Insoluble salts Mix two soluble acids and Bases The salt will come out as a precipitate The precipitate is then filtered and dried. The filter paper will contain an insoluble salt. To determine the exact volume of acid and base required to make the salt, titration is carried out.

Making Soluble Salts

Mix the insoluble base into the aqueous solution of the acids. Dissolve the base into the acid until no base can be dissolved. Filter the solution to remove excess undissolved base. The run off is then crystallized to remove all the water. After evaporation the crystals will collect at the size of the vessel. The crystals can then be dried.

ELECTROLYSIS

• Electrolysis – The breaking of ionic compound by passing electricity.
• Electrolyte – The substance that undergoes Electrolysis
• Electrode – The two conducting rods dipped in an electrolyte
• Cathode – Where Cations (+ve charge ions) go. So it is negatively charge electrode
• Anions – Where anions (-ve charge ions) go. So it is positively charged.

ELECTROLYSIS OF MOLTEN IONIC COMPOUNDS

Ionic compounds conduct Electricity when in molten or in solution as the ions are free to move when they’ are in solvent or dissolved in water. Molten Sodium Chloride NaCl                   Na⁺(goes towards cathode) + Cl^–(goes towards anode) Cathode                    Reduction Na⁺ + e^–                  Na(s) Anode                        Oxidation 2Cl^–                  Cl₂(g) + 2e^– O – Oxidation I – Is L – Loss R – Reduction I – Is G – Gain

ELECTROLYSIS IN SOLUTIONS

In Solution the water also gets ionized and dissociate into H+ and OH- which also competes with the ionic compounds ions to discharge. Sodium Chloride Solution Ions H⁺ + OH^– Na⁺ + Cl^– At Cathode 2H⁺ + 2e^–                          H₂(g) Rule – At the cathode, the element with least reacitivity will get discharged and gains electrons. For that we have to look at the reactivity series At Anode 2Cl^–                  Cl₂ + 2e^– For Anode, the rule is – Halide> OH^– > other negative ions Remaining Solution Na⁺ + OH^– Potassium Sulphate solution Ions K⁺ + SO₄^2- H⁺ + OH^– At Cathode 2H⁺ + 2e^–                          H₂ At Anode 4OH^–                  O₂ + 2H₂O + 4e^– Remaining Solution K₂SO₄

ELECTROLYSIS OF ALUMINIUM OXIDE

Bauxite an ore of aluminium is used which contains aluminium in the form of aluminium oxide. Al₂O₃                 Al³⁺ O^2- Bauxite is mixed with cryolite. Cryolite lowers the melting point of aluminium oxide making it melt at a lower temperature. At Anode 2O^2-                  O₂ + 4e^– Oxygen evolved reacts with graphite electrode forming carbon dioxide. Therefore, they are used up and needs regular replacing At Cathode Al³⁺ + 3e^–                          Al(s) O₂ + C                 CO₂ Baneer 6

Disclaimer:

I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it. References: BBC Bitesize Wikipedia Wikimedia Commons Image Source: Wikipedia Wikimedia Commons Flickr Pixabay