Q1) What conditions are present that enable rusting? Q2) How do you think rusting of the Eiffel Tower is prevented? Q3) Why is it important to prevent the Eiffel Tower from rusting? Q4) How could the design of the Eiffel Tower have been improved in order to prevent rusting?

Q3) Tourist attraction – makes 22 million euros a year. Q1) Water and Oxygen Q2) It is painted once every 7 years – this takes 18 months to complete and costs 4million euros! Q3) Tourist attraction – makes 22 million euros a year. Q4) Any reasonable answer Q4 sparked a good debate. Suggestions included: wood (fire risk), Al (not discovered), Au (too expensive), plastic (unsightly, unstable).

Rusting

What you need to know about rusting Rusting is the corrosion of iron (& steel). Other metals can CORRODE but not rust It is an oxidation process (addition of oxygen) Rust is hydrated iron oxide Both water and oxygen (from the air) are required for rusting Salt and other electrolytes (e.g. acid) can speed up rusting

Group practical: Design an experiment to prove that oxygen and water are needed for rusting to occur and whether salt increases the rate of rusting Work in groups of 2 You will be given the following Nails Stoppers Paint Salt – at least 4 types Access to water Anhydrous calcium chloride

Write answers in the back of your book What is the question? Write answers in the back of your book Only iron 2) Water AND oxygen 3) Anhydrous calcium chloride 4) Salts and other electrolytes 5) Hydrated iron oxide

How can we prevent this from happening?

Rust prevention

There are 2 main methods to help prevent rusting 1) Putting a barrier between the metal and the air and moisture e.g. grease, paint, plastic, unreactive metal 2) Sacrificial protection-The iron is covered or connected to a more reactive metal so it will ‘corrode’ ahead of the iron e.g. Magnesium or Zinc

Decide whether these chemicals will react together when heated Magnesium + copper(ll) oxide Iron + magnesium oxide Zinc + magnesium oxide Copper + zinc oxide Calcium + zinc oxide For those that react: Write a word equation Write a balanced equation

Answers Magnesium + copper(ll) oxide → Copper + magnesium oxide Mg + CuO → Cu + MgO Iron + magnesium oxide – No Reaction Zinc + magnesium oxide – No Reaction Copper + zinc oxide – No Reaction Calcium + zinc oxide → Zinc and Calcium oxide Ca + ZnO → Zn + CaO

Displacement reactions of solutions A more reactive metal will displace a less reactive metal from a solution of one of its salts. For example: magnesium + copper(II) sulfate → copper + magnesium sulfate Mg(s) + CuSO4(aq) → Cu(s) + MgSO4(aq) In this reaction, the blue colour of the copper(II) sulfate fades as it is used up (magnesium sulfate solution is colourless). We would also see copper metal forming.

Decide whether these will react: Iron + copper(ll) sulphate solution Silver + calcium nitrate solution Zinc + copper (ll) sulphate solution For those that react: Write a word equation Write a balanced equation (extension)

Answers Iron + copper(ll) sulphate solution – No Reaction Silver + calcium nitrate solution – No Reaction Zinc + copper (ll) sulphate solution → Copper and zinc sulphate solution Zn(s) + CuSO4(aq) → Cu(s) + ZnSO4(aq)