Do Now!

Describe how aluminium can rust, and how it’s different to rusting iron (use the information found in the “Iron and Aluminium” worksheet)

Aluminum is very, but is usually covered by a thin “skin” of oxide, which protects the metal underneath from attack by oxygen, water, or acids.

Iron is less active, but its oxide skin is porous in water. It doesn’t protect the metal underneath from oxygen in wet conditions, and the whole of the metal eventually reacts to form the oxide.

Iron and Aluminum (continued) and revision

Miss Jan

Iron rust is porous –

allows oxygen to enter the metal, which allow more

rusting

Rusting Aluminium?

Aluminum is actually very prone to corrosion. However, aluminum corrosion is aluminum oxide, a very hard material that actually protects the aluminum from further corrosion. Aluminum oxide corrosion also looks a lot more like aluminum, so it isn't as easy to notice as rusted iron.

“How to prevent rusting” sheet

Each table group read through and summarize one method of preventing rust. Then report to back to the class – report should contain:What is this method?How does it work?

Sacrificial metal

To be bolted onto the hull of the boat

Why is it labeled “do not paint”?

Galvanised iron

Coat of zinc – prevent water or oxygen from reacting with iron

Electroplating

Chrome and nickel coating

Method How it works Where it’s used

Painting The paint stops oxygen and water from reaching the iron beneath.

Cars, roofs

Greasing The paint stops oxygen and water from reaching the iron beneath.

Machinery

Electroplating

A coating of a metal like tin or chromium stops oxygen and water reaching the iron.

Car and bike parts

Galvanising A coating of zinc stops oxygen and water reaching the iron and also corrodes before the iron.

Roofs, sheds

Alloying Combining the iron with chromium or nickel to make stainless steel slows down rusting.

Kitchen surfaces

Questions about rusting

1. Iron oxide

2. Iron, water, oxygen

3. Iron + oxygen iron oxide

4. Brass (Cu + Zn) does not rust. Steel (99% Fe) rusts

5. Painting provides a barrier to water and oxygen, preventing them from reacting with iron

6. Two sacrificial metals: magnesium and zinc

7. Hull of ship or drilling platform, hot water heater

8. Copper – the steel/Fe will become the sacrificial metal

9. Zinc10. Zinc prevents water or oxygen

from reaching iron. Also acts as sacrificial metal (will corrode before iron)

Revision

Barrier activityQuiz

1. Give one example of the use of metals relating to each of the different physical properties.

a) Ductileb) Sonorousc) Malleabled) High melting pointe) Lustrousf) High electrical conductance

Gold - earringsBrass – cow bells

Steel – car bodiesCooking pots - steel

Silver - mirror

Copper – electrical wires

Quiz

2. Name the elements represented by the following symbols.

Al Fe Sn Pb Na Au S I He Cu

3. Draw the atom diagram for

Electron:

Proton:

Neutron:

Al27

13131327 – 13 = 14

13p14n

Rusting

1. Only one metal rusts. Which one is it?2. What is the chemical name for rust?3. What conditions are needed for rusting

to occur?4. Give at least four different methods of

preventing rusting and explain how each one works.

5. Give an example of a situation in which each of these methods is used.

Method How it works Where it’s used

Painting The paint stops oxygen and water from reaching the iron beneath.

Cars, roofs

Greasing The paint stops oxygen and water from reaching the iron beneath.

Machinery

Electroplating

A coating of a metal like tin or chromium stops oxygen and water reaching the iron.

Car and bike parts

Galvanising A coating of zinc stops oxygen and water reaching the iron and also corrodes before the iron.

Roofs, sheds

Alloying Combining the iron with chromium or nickel to make stainless steel slows down rusting.

Kitchen surfaces

The reaction of metals with water

1. What is the general word equation for the reaction of metal with water?

Metal + water metal hydroxide + hydrogen

2. Write the word equation for the reaction of calcium with water.

Calcium + water calcium hydroxide + hydrogen

2. How do you test for the gas produced in the reaction in Q3?

Pop test – put flame near collected gas, if hydrogen was present, a squeaky pop should be heard.

The reaction of metals with acid

1. What is the general word equation for the reaction of metal with acid?

metal + acid salt + hydrogen2. Write the word equation for the reaction

of zinc with hydrochloric acid.Zinc + hydrochloric acid Zinc chloride + hydrogen

1. Write the general word equation for the reaction of metals with oxygen.

Metal + oxygen metal oxide

2. Write the word equation for the reaction of magnesium with oxygen.

Magnesium + oxygen Magnesium oxide

The reaction of metals with oxygen

Magnesium reacts slowly with hot water and doesn’t react with cold water. Calcium reacts rapidly with hot water and slowly with cold water. Sodium explodes in hot water and reacts rapidly with cold water.

Which of these three metals is the most active chemically?

Which metal is the least active?

Sodium

Magnesium

Think about it…

1. How could you make zinc sulfate from zinc metal?

2. Could you make copper sulfate in the same way? Explain your answer.

3. Why would it not be a good idea to store vinegar (dilute acetic acid) in aluminium cans?

4. Car batteries contain dilute sulphuric acid. Why are battery cases made of plastic rather than steel?

By reacting Zn with dilute sulfuric acid

No

Acid in vinegar would react with Al and make holes in can

As above

Atomic alphabet

Make an “Atomic alphabet”Ask your partner to guess the

wordsFor example, “My name starts with

the letter A, and I am the smallest particle of an element.”