09/03/2022
Redox reactions
Starter: Why do metals tarnish?
Metals react with oxygen to form metal oxides in an oxidation
reaction.
metal
+
oxygen
metal oxide
The reactions are oxidation reactions because the metal gains
oxygen.
Oxygen can be removed from metal oxides in chemical
Fill in the Blanks
1.
2.
3.
4.
5.
6.
Aluminium + Oxygen  Aluminium _______
Iron + ______  Iron oxide
______ + Oxygen  Lithium oxide
Sodium + Oxygen  ______ _______
Copper oxide + Carbon  _____ + Carbon
dioxide
Iron(II)oxide + Carbon  Iron + _____ _____
For each one decide whether the metal is oxidised or reduced?
Challenge: convert the word equations into symbol equations.
1.
2.
3.
4.
5.
6.
Aluminium + oxygen  Aluminium oxide
Iron + oxygen  iron oxide
Lithium + oxygen  lithium oxide
Sodium + oxygen  sodium oxide
Copper oxide + carbon  copper +
carbon dioxide
Iron(II)oxide + carbon  Iron + carbon
dioxide
Peer Mark /12
• Oxidised
• Oxidised
• Oxidised
• Oxidised
• Reduced
• Reduced
Practical- Burning Magnesium Ribbon
• Identify a group (2-3)
• One person collect:
• tongs and goggles
• Bunsen burner, heatproof mat and splint
• Light Bunsen from partner
• Take a small piece of magnesium ribbon and hold in the
hot part of the flame using tongs
DO NOT LOOK DIRECTLY AT THE FLAME
• Place on heat proof mat when finished
• Turn gas off
• pack away
Equipment
Goggles, bunsen burner, heatproof mat, tongs, magnesium
ribbon, splint
Questions
1. Describe the appearance of the magnesium ribbon before, during
and after heating.
2. Write the word equation for the reaction
3. Write the balanced symbol equation
4. Is magnesium oxidised or reduced?
Challenge
5. What type of bond is formed
Answers
Describe the appearance of the magnesium ribbon before, during and after heating.
Shiny silver
Bright white flame
White powder
Write the word equation for the reaction
Magnesium + Oxygen  Magnesium oxide
Write the balanced symbol equation
2Mg(s) + O2(g)  2MgO(s)
Is magnesium oxidised or reduced?
Oxidised
Challenge
What type of bond is formed
Ionic
Whiteboard Questions
Draw a dot and cross diagram to show arrangement of electrons in
magnesium and oxygen atoms (before bonding)
Draw a dot and cross diagram to show arrangement of electrons in
magnesium and oxygen ions (after bonding)
Describe the movement of electrons.
2+
2-
Discuss
Is Magnesium oxidised or reduced?
Is Oxygen oxidised or reduced?
Half equations
2Mg + O2  2MgO
Can you rearrange the terms to make the 2 half equations balance
(charge and number of ions/atoms)
Mg Mg2+ e- 
O2 O2- e- 
Extension
Lithium + Oxygen  Lithium oxide
Word equation
2Li + O2  Li2O
Balanced symbol equation
Li  Li+ + eO2 +4e-  2O2-
Half equation