Topic 5 - Separate chemistry 1

Question 1

What type of metal are most metals?

Answer 1

Transition metals

Question 2

Are the melting points of transition metals usually high or low?

Answer 2

High

Question 3

Are the densities of transition metals usually high or low?

Answer 3

High

Question 4

Are transition metal compounds normally colourless or colourful?

Answer 4

Colourful

Question 5

Are transition metals and their compounds good or poor catalysts? What is an example to show this?

Answer 5

They are good catalysts. For example, iron is the catalyst used in the Haber process for making ammonia.

Question 6

What does it mean for a metal to be oxidised?

Answer 6

It forms a metal oxide when in the presence of oxygen and water

Question 7

What does the oxidation of metals result in?

Answer 7

Corrosion

Question 8

What type of reaction is it when a metal is oxidised? What does this mean?

Answer 8

A redox reaction - the oxygen undergoes REDuction (it gains electrons) and the metal undergoes OXidation (it loses electrons)

Question 9

What is rusting?

Answer 9

Corrosion of iron

Question 10

What are the main ways of preventing rusting? What are examples of them?

Answer 10

1) Exclusion of oxygen
2) Exclusion of water

Both 1 and 2 can be done by coating the iron with a barrier which can keep out oxygen, water or both.

Painting is one example. Oiling/greasing has to be used when moving parts are involved e.g. bike chains.

3) Sacrificial protection - placing a more reactive metal with the iron. The water and oxygen react with sacrificial metal, not the iron.

E.g. galvanising - coat of zinc (acts as sacrificial protection and a barrier)

Question 11

What is electroplating?

Answer 11

Coating the surface of a metal with another metal using electrolysis

Question 12

In electroplating, what are the cathode, anode and electrolyte?

Answer 12

cathode = object you're going to electroplate
anode = bar of metal you're using for the plating
electrolyte = solution containing the metal ions of the metal you're plating

Question 13

How can electroplating be used to improve the appearance of metal objects?

Answer 13

Items such as jewellery and decorative items can be electroplated with shiny, attractive metals like gold and silver which improves their appearance

Question 14

How can electroplating be used to improve the resistance to corrosion of metal objects?

Answer 14

Household objects like cutlery and cooking utensils can be electroplated with unreactive metals which don’t corrode easily which improves their resistance

Question 15

Why are pure metals malleable?

Answer 15

They have a regular arrangement of identical atoms and the layers of ions can slide over each other (tinyurl.com/puremetalslide)

Question 16

How are alloys made?

Answer 16

By adding another element (non-metal or another metal) to a metal

Question 17

Why does converting pure metals into alloys often increase the strength of the product?

Answer 17

• Different elements have different sized atoms.
• So, for example, when an element such as carbon is added to pure iron, the smaller carbon atoms will UPSET the layers of pure ion atoms.
• This makes it more difficult for them to slide over each other (tinyurl.com/alloystructure).

Question 18

How are steels made?

Answer 18

By alloying pure iron with small amounts of carbon (and sometimes extra metals e.g. stainless steel)

Question 19

What are 3 advantages of making steel from iron?

Answer 19

1) Steel is harder than iron
2) Stronger than iron (as long as amount of carbon is less than about 1%)
3) Much less likely to rust (stainless steel (made from more than just iron and carbon) is corrosion-resistant)