13 - Transition Metals, Alloys & Corrosion

Question 1

Describe the location of transition metals in the periodic table

Answer 1

Between groups 2 & 3

Question 2

What are the physical properties of transition metals?

Answer 2

• Malleable
• Ductile
• Good conductors of electricity
• Shiny when polished
• High densities
• High Mp & Bps
• Shows Catalytic activity

Question 3

Suggest a reason that explains why catalytic converters usually contain iron or platinum?

Answer 3

Transition metals & their compounds show catalytic activity

Question 4

What does the oxidation of metals result in?

Answer 4

Corrosion

Question 5

What is Tarnish?

Answer 5

A thin layer that forms on a metal due to oxidation

Question 6

What is the purpose of tarnish on metals?

Answer 6

Stops further oxidation by stopping oxygen reaching the metal

Question 7

When do metals oxidise in terms of electronic configurations?

Answer 7

When they lose electrons

Question 8

What is sacrificial protection?

Answer 8

Using a more reactive metal to protect iron from rusting

Question 9

What is corrosion?

Answer 9

When a metal continues to oxidise and so the metal becomes weaker over time

Question 10

What is Rusting?

Answer 10

The corrosion of iron or steel

Question 11

Explain how iron rusts

Answer 11

Iron rusts when it reacts w/ water or o2

Rust flakes off rusty iron, which exposes more metal to the air & water
—> Therefore, Iron continues to corrode & weaken

Question 12

What are the different methods to prevent rusting of Iron?

Answer 12

• Exclusion of oxygen
• Exclusion of water
• Sacrificial protection

Question 13

How can the rusting of Iron be prevented by Exclusion of air?

Answer 13

Storing metal in an unreactive atmosphere of nitrogen or argon
—> Prevents o2 in air reacting with the Iron

Question 14

How can the rusting of Iron be prevented by Exclusion of water?

Answer 14

E.g. Using a desiccant powder that absorbs water vapour
—> Prevents water reacting with the Iron - causes rusting

Question 15

How can the rusting of Iron be prevented by Sacrificial protection?

Answer 15

Using another more reactive metal will oxidise more easily than Iron - o2 reacts with them rather with the Iron or steel object

Question 16

What metals are commonly used for Sacrificial protection?

Answer 16

• Magnesium
• Zinc

Question 17

Why does Zinc & Magnesium react more easily than Iron?

Answer 17

The more reactive a metal is, the more easily it loses electrons

Zinc & Magnesium loses electrons more easily than Iron does - more easily oxidised

Question 18

Give an example of an unreactive metal?

Answer 18

Gold

Question 19

What is electroplating?

Answer 19

Coats the surface of one metal with a thin layer of another metal

Question 20

Explain how electroplating is used to improve the appearance of metals

Answer 20

Silver & Gold can be electroplated onto cheaper ‘base metals’
—> Produces cheap, attractive jewellery that is cheaper than solid gold or silver

Question 21

Explain how electroplating is used to improve a metals ability to resist corrosion

Answer 21

A thin layer of metal that resists corrosion can be electroplated onto vehicle & boat parts to stop air & water reaching the steel below
—> Prevents rusting

Question 22

What objects do you need to electroplate a metal object?

Answer 22

• An Anode - Made from the plating metal
• A Cathode - Metal object itself
• An Electrolyte - A solution containing ions of the plating metal

Question 23

What is galvanising?

Answer 23

Coating iron & steel objects with Zinc

Question 24

How does galvanising improve the corrosion resistance?

Answer 24

By stopping water reaching the iron or steel by acting as a sacrificial metal
—> Sacrificial protection can continue even if the Zinc layer is damaged

Question 25

How can **galvanising** be carried out?

Answer 25

* Using electroplating * Dipping the object in molten zinc

Question 26

Describe why you **shouldn't** buy **damaged food tins**

Answer 26

* Food cans are made from steel * Inner surfacing is protected from rusting by electroplating with tin * Steel will rust faster if tin layer is damaged. Iron is more reactive than tin - acts as a sacrificial metal to protect the tin

Question 27

What is an **alloy**?

Answer 27

A mixture of a metal element with one or more other elements, usually metals

Question 28

How are **alloy steels** made?

Answer 28

By deliberately adding other elements to iron

Question 29

Explain why **pure metals** aren't as strong as **alloys**

Answer 29

Pure metals - same size atoms & regularly arranged. Layers move past each other if enough force is applied Alloys - atoms of other elements present is other sizes. This distorts the regular structure, makes it more difficult for the layers to slide past each other

Question 30

What does the **uses** of a **metal or alloy** depend on?

Answer 30

* Chemical properties * Physical properties

Question 31

What are the **properties** of **aluminium**?

Answer 31

* Resists corrosion * Can't conduct electricity * Strong * Less dense * Cheap