Transition metals, alloys and corrosion

Question 1

where are the transition metals placed?

Answer 1

placed in the central part of the periodic table.

Question 2

properties of transition metals? (4)

Answer 2

high melting points
high densities
they form coloured compounds
they (and their compounds) can act as catalysts

Question 3

what coloured compounds do metals or non metals often form?

Answer 3

white or colourless compounds

Question 4

how is Iron an exception? (4)

Answer 4

-it has the typical properties of transition metals

-high melting and boiling point + high density
-pale green
-used as a catalyst in the haber process

Question 5

what do metals do in air?

Answer 5

oxidise

Question 6

what do very unreactive metals NOT do?

Answer 6

oxidise at all

Question 7

what is corrosion?

-what does it eventually become?

Answer 7

when a metal continues to oxidise and becomes weaker over time

-metal oxide

Question 8

when does rusting occur?

-how could you prevent this?

Answer 8

when iron or steel reacts with oxygen and water

-keeping them away from water and oxygen

Question 9

Explain whether iron is oxidised or reduced when it forms rust.

Answer 9

Iron is oxidised because it gains oxygen during rusting.

Question 10

how can rusting from oxygen and water be prevented (specific)? (2)

Answer 10

oxygen : storing the metal in an atmosphere of unreactive nitrogen or argon

water : storing the metal with a desiccant

Question 11

what is a dessicant?

Answer 11

a substance that absorbs water vapour, so it keeps the metal dry.

Question 12

state some physical barriers to prevent water and oxygen from causing rusting: (3)

Answer 12

painting
oiling and greasing
coating with plastic or a metal (electroplating)

Question 13

Explain why a bike chain is protected from rusting by oiling it, rather than by painting it. (2)

Answer 13

oil lubricates the chain, helping it to move smoothly.
-paint flakes off when bike is ridden, exposing steel chain to air and water again.

Question 14

what does electroplating involve?

Answer 14

using electrolysis to put a thin layer of a metal on an object

Question 15

describe the components in the electroplating process: (3)

Answer 15

-cathode (negatively charged electrode) is the iron or steel object
-anode (positively charged electrode) is the plating metal
-electrolyte contains ions of the plating metal

Question 16

what does electroplating improve? (2)

Answer 16

-corrosion resistance of metal object
-appearance

Question 17

how can iron also be protected? (sacrificial protection)

Answer 17

if it is in contact with a more reactive metal

Question 18

how does the process of sacrificial protection work?
-why is it useful?(2)

Answer 18

-more reactive metal oxidises more readily than iron, so it ‘sacrifices’ itself while the iron does not rust.
-once metal has corroded away, it can simply be replaced.

Question 19

what is galvanising? (1)

-how does it work? (2)

Answer 19

when iron is coated in zinc

-since zinc is more reactive then iron, it acts as a sacrificial method
-stops oxygen and air reaching iron, even if it is scratched

Question 20

The inside of a steel food can is electroplated with tin, a less reactive metal than iron. It provides a physical barrier to oxygen and water, stopping the can rusting. Explain why the inside of the can rusts very quickly if the layer of tin is broken. (3)

Answer 20

-Oxygen and water can reach the steel when the layer is broken.
-Iron is more reactive than tin, so it oxidises more readily than tin.
-The damaged can rusts faster than if the tin was not there at all.

Question 21

what is an alloy?

Answer 21

a mixture of two or more elements, where at least one element is a metal

Question 22

why is converting pure metals into alloys often convenient?

Answer 22

it increases the strength of the product

Question 23

what do solid metals have in terms of composition?
and what happens when a force is applied to a metal?

Answer 23

-a regular lattice structure.
-layers of atoms can move past each other.

Question 24

what happens when it is more difficult to move through the regular lattice structure of solid metals?

Answer 24

The more difficult it is for the layers to move, the more force is needed and the stronger the metal.

Question 25

explain why alloys have a higher tensile strength compared to their (separate) metal counterparts? (4)

what does this make brass?

Answer 25

-atoms of different elements have different sizes.
-this distorts the regular lattice structure in brass
-so layers of atoms cannot slide over each other so easily.
-this makes brass stronger than copper or zinc alone.

Question 26

what are alloy steels?

Answer 26

Alloy produced by mixing iron with one or more other metals.

Question 27

what are the properties of mild, tool and stainless steel?

Answer 27

mild = Malleable, ductile
tool = Hard, resistant to high temperatures
stainless = Hard, resistant to rusting

Question 28

what is mild steel useful for making?

what is a problem which occurs because of this and how could it be fixed?

Answer 28

car body parts because it is easily pressed into shape.

mild steel rusts, however it can be protected by galvanising and painting

Question 29

what is tool steel used for?
and why?

Answer 29

Tool steel is useful for making drill bits.
These do not easily become damaged by the heating caused by friction during drilling.

Question 30

Explain why stainless steel is used to make washing machines and dishwashers. (2)

Answer 30

Washing machines and dishwashers contain water.
This would cause other steels to rust, but stainless steel does not rust.

Question 31

what is the equation for the reaction of iron, oxygen and water?

Answer 31

Iron + oxygen + water → hydrated iron(III) oxide

Question 32

what does Hydrated iron(III) oxide (rust) look like?

Answer 32

orange-brown substance seen on the surface of rusty objects.