(2.18-2.21) Reactivity Reactions

What does iron need to rust?

Oxygen and Water need to be present

Why can the rusting of iron be damaging?

Over time, structures made of iron weaken as the iron rusts and the rust flakes off.

What are 3 ways to prevent the rusting of iron?

• Barrier methods

• Galvanising

• Sacrificial Protection

Explain and evaluate barrier methods to prevent rusting.

• Done by coating the iron with paint/oil/grease

• to prevent water and oxygen coming into contact with it

  • if the barrier is scratched, the iron will rust

  • rust is porous, so one scratch will cause it to begin internally rusting

Explain and evaluate sacrificial methods to prevent rusting.

• A more reactive metal (Zn) can be attached to it

• the more reactive metal will corrode first

• protecting the less reactive metal

  • the sacrificed metal needs to be replaces

Explain and evaluate galvanising to prevent rusting.

• The iron is coated with a layer of zinc by electroplating/dipping into molten zinc.

• ZnZO₃ acts as a barrier

• if the coating is damaged, iron protected by sacrificial protection

What is oxidation?

A reaction in which a substance

• gains oxygen

• loses electrons

What is reduction?

A reaction in which a substance

• loses oxygen

• gains electrons

What is a redox reaction?

Oxidation and reduction can’t occur independently of each other

so these reactions are called redox reactions.

What is an oxidising agent?

The reactant supplied the oxygen

What is a reducing agent?

The reactant removing/taking the oxygen

What happens when Mg reacts with HCl?

• dissolved quickly

• heats up

• hydrogen given off

• colourless solution remains

What happens when Mg reacts with H2SO4?

• rapid bubbling

• splint goes pop

• metal dissolves

What happens when Fe reacts with HCl?

• very slow bubbling

What happens when Fe reacts with H2SO4?

• slow reaction

• small bubbles visible

What happens when Zn reacts with HCl?

• bubbles given off

• metal slowly dissolves

What happens when Zn reacts with H2SO4?

• metal dissolves forming colourless solution

• gas given off slowly