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Chemistry Igcse > C10 > Flashcards

C10 Flashcards

1
Q

What are the physical properties of metals?

A

Conduct heat and electricity
Malleable (hammered into different shapes)
Ductile (wire)
Lustrous (shiny)
High density
High melting/boiling points
Form positive ions (electron loss)
Form basic oxides
Strong
Solid at room temp (-mercury)

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2
Q

Explain metallic bonding

A

Metal -> regular lattice -> tightly pack layers

Outer electrons separated from atoms creating a ‘sea of electrons’
> electrons delocalized -> free to move thought the whole structure
> positive ions

Metal ions are attracted to the sea of electrons -> metallic bonding

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3
Q

How does the structure of metals explain:
High melting and boiling points

A

Strong attractive forces between ions -> strong metallic bonds

Lots of heat required to break the bonds

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4
Q

How does the structure of metals explain:
Conducting heat and electricity

A

Delocalized electrons -> conduct heat and electricity

Metals heated -> electrons gain kinetic energy -> moves faster -> electrons transfer gained energy through the metal

Electrons carry charge -> electrons enter on end of the metal -> causes delocalized electrons to displace itself -> electrons flow -> electricity is conducted

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5
Q

How does the structure of metals explain:
Metals strength, malleability, ductility

A

Metals hit -> layers of metal ions can slide over each other -> no shatter
> layers of ions can take different positions

Bonding is not disrupted:
Outer electrons so not ‘belong’ to any one ion so delocalized electrons can move

This property makes metals malleable and ductile

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6
Q

How does the structure of metals explain:
Corrosive

A

Corrosion -> gradual destruction of a metal due to reactions with other chemicals in its environment
>makes metals weaker

Coating the surface with paint/certain chemicals -> protection

Metals corrode at different rates
> gold -> uncreative -> does not corrode

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7
Q

Define alloy

A

An alloy is a MIXTURE of 2+ metals or a metal with a non-metal such as carbon

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8
Q

Why are alloys used? How does this relate to properties of alloys as opposed to pure metals?

A

Alloys often have different properties to their metals they contain:
> strength
> hardness
> resistance to corrosion
> resistance to extreme temperatures

Alloys contain atoms of different sizes -> distorts regular arrangement of atoms
> makes it more difficult for layers to slide -> alloys are harder than pure metals

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9
Q

What are some common alloys and their uses?

A

Brass = copper + zinc
> stronger
> used in musical instruments, door knobs, ornaments

Stainless steel = iron + other elements (chromium, nickel, carbon)
> cutlery
> because of its hardness, resistance to corrosion

Iron + tungsten
> hard and resistant to high temps

Iron + chromium or nickel
> resistant to corrosion

Aluminium + copper, manganese, silicon
> aircraft body production
> stronger but low density

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10
Q

What are the different types of steel (properties or iron changed by the controlled use of additives)
Name:
Amount/element alloyed with:
Use:
Property:

A

Pure iron -> not very useful because it is too soft and rust easily
Too much carbon -> brittle
Too little carbon -> no strong enough

Mild steel:
> 0.25% carbon
> used in: car body panels, wires
> soft + malleable

High carbon steel:
>0.5 - 1.4% carbon
> tool and chisel
> hard

Low alloy steel:
> 1 - 5% of another metal (CR, NI, TI)
> construction, bridges, high speed tools
> hard, strong, low ductility + malleability

Stainless steel:
> 20% chromium + 10% nickel
> cutlery, sinks, chemical plants
> strong, resistant to corrosion

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11
Q

List metals in order of reactivity (+ carbon and hydrogen)
(Hint: please send (lions) cats, monkeys, and cute zebras into hot countries signed Gordon)

A

Potassium
Sodium
lithium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Hydrogen
Copper
Sliver
Gold

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12
Q

State the reaction by the metal in:
Cold water

A

Potassium
> react violently

Sodium
> reacts quickly

Calcium
> reacts less strongly

————
> metal below calcium -> react with steam not cold water
> metal below calcium + steam -> metal oxide + hydrogen

Magnesium
> slow reaction (with steam)

Aluminium
> slow reaction (with steam)

Carbon
> —

Zinc
> very slow reaction (with steam)

Iron
> very slow reaction (with steam)

Hydrogen
> more reactive than hydrogen:
-> metal + water -> metal hydroxide + hydrogen gas

Copper
> no reaction

Sliver
> no reaction

Gold
> no reaction

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13
Q

State the reaction by the metal in:
Acid

A

Potassium
> reacts violently

Sodium
> reacts violently

Calcium
> reacts vigorously

Magnesium
> reacts vigorously

Aluminium
> reacts readily

Carbon
> —

Zinc
> reacts less strongly

Iron
> reacts less strongly

Hydrogen
> metals above hydrogen will react to dilute metals
> metal + acid -> salt + hydrogen

Copper
> no reaction

Sliver
> no reaction

Gold
> no reaction

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14
Q

State the reaction by the metal in:
Oxygen

A

Potassium
> reacts quickly

Sodium
> reacts quickly

Calcium
> reacts readily

Magnesium
> reacts readily

Aluminium
> reacts readily

Carbon
> under carbon in reactivity series -> carbon will displace them in their oxides forming carbon dioxide
-> reduction

Zinc
> reacts

Iron
> reacts

Hydrogen
> —

Copper
> reacts

Sliver
> reacts

—————-
> metal + oxygen -> metal oxide

Gold
> no reaction

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15
Q

How does loss of electrons relate to the reactivity of a metals?

A

Metal atoms → positive ions by loss of electrons when they react with other substances

The tendency of a metal to lose electrons is a measure of how reactive the metal is

A metal that is high up on the series loses electrons easily and is thus more reactive than one which is lower down on the series

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16
Q

Explain the displacement reaction between metals and aqueous solutions of metal salts

A

> metal (1) will displace metal (2) that is LOWER on the reactivity series
-> metal (2) (less reactive) must be a solution of its salt

> this is because metal (1) is more reactive (loss electrons and creates ions more readily) -> better reducing agents

> less reactive metal (2) is better electron acceptor -> is reduced (gains electrons)

This can be used to to deduce the order of reactivity (if you don’t know them)

Metals can also displace oxides:
Ex: Iron (II) oxide + aluminium -> iron + aluminium oxide

17
Q

Give an example of a displacement reaction between metals and aqueous solutions of metal salts
Magnesium and copper sulphate

A

Magnesium + copper sulphate
> magnesium -> reactive
-> can displace copper from copper sulphate solution

> magnesium loses its electrons easily and ions of copper will gain these electrons -> forms elemental copper

Magnesium + copper sulphate -> magnesium sulphate + copper
Mg + CuSO4 -> Mg SO4 + Cu

18
Q

How can you deduce the order of reactivity from a given seat of experimental result?

A

Observed through reactions between metals, water, acids, oxygen

> more vigorous reaction -> higher up on reactivity scale
-> will have to use a combination of reactions (ex: with water)

> less reactive metals react slowly or not at all
-> will have to use a combination of reactions (ex: dilute acid)

> temperature change in a reaction can also be used
-> greater temperature change -> more reactive

19
Q

How does a metals reactivity determine its method of extraction?

A

Most metals found in earths crust are combined with other elements in ORES (usually an oxide)
> iron is found combined with oxygen -> haematite and magnetite

The reactivity of a metal determines method of extraction
> above carbon -> electrolysis
-> ex: aluminium from bauxite

> below carbon -> extracted by reduction
-> iron from haematite

> platinum, gold, silver, copper -> occur native

20
Q

What metals use electrolysis/reduction/found as pure for extraction?

A

Electrolysis:
> Large amounts of electricity needed -> expensive
> electrolysis of molten chloride or oxide
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium

Reduction:
> extracted by heating its reducing agent
> cheap
Zinc
Iron

Found as pure:
Copper
Silver
Gold

21
Q

What is the reaction in the extraction of iron from haematite (chemical equation)?

A

C + O2 -> CO2
> burning of carbon to provide heat + make CO2:

C + CO2 -> 2CO
> reduction of CO2 to CO

Fe2O3 + 3CO -> 2Fe + 3CO2
> reduction of iron (III) oxide by CO

CaCO3 -> CaO + CO2
> thermal decomposition of limestone to produce CaO

CaO + SiO2 -> CaSiO2
> formation of slag

22
Q

Explain the process of extraction of iron using a blast furnace

A

Raw materials: iron ore, coke (impure carbon), limestone added to top of the furnace
> hot air blown into the bottom

ZONE 1 (BOTTOM): oxidation
> coke burns in hot air -> carbon dioxide
> reaction exothermic -> heats the furnace
> Carbon + oxygen -> carbon dioxide

ZONE 2 (MIDDLE): redox
> at high temp -> coke reacts with CO2 to form CO
> CO2 reduced to CO
> carbon + carbon dioxide -> carbon monoxide

ZONE 3 (TOP): redox
> carbon monoxide reduces iron (III) oxide
-> iron ore -> iron
> iron will melt and collect at bottom of furnace (taped off)
> iron (III) oxide + carbon monoxide -> iron + carbon dioxide

> some iron (III) oxide reacts with carbon to form carbon dioxide
Iron (III) oxide + carbon -> iron + carbon dioxide

SLAG:
> limestone added to the furnace to remove impurities
-> limestone thermally decomposes to form calcium oxide
> Calcium oxide reacts with silicon dioxide (impurity) -> calcium silicate
-> this is slag -> collects at bottom on top of iron (tapped off)
> CaO + SiO2 -> CaSiO3

23
Q

What are the uses of aluminum?

A

Airplane bodies
> high strength to weight ratio
> low density

Overhead power cables
> good conductor of electricity
> low density

Saucepans
> good conductor of heat

Food can
> non-toxic
> resistant to corrosion and acidic food stuffs

Window frames
> resistant to corrosion

24
Q

Describe and explain the apparent unreactivity of aluminum

A

Aluminum -> high in reactivity series
> but in reality its doesn’t react with water and with acid is slow

That is because it reacts readily with oxygen -> forms protective layer of aluminum oxide (THIN)
> layer prevents reaction with water and dilute acids
> aluminum can behave as if unreactive

25
Q

What is rust?

A

A chemical reaction between iron, water and oxygen to form hydrated iron (III) oxide AKA rust

Rust can be prevented with barriers such as:
> grease
> paint
> oil
> plastic

ONLY IRON AND STEEL CAN RUST

26
Q

Explain sacrificial protection (+ an example)

A

More reactive metals attached to less reactive metals
> more reactive metal will corrode first
> protects the less reactive metal from rusting

Ex: using zinc bars on the side of steel ships
> zinc more reactive than iron
> Zn -> Zn2+ + 2e-

27
Q

Explain galvanizing (using example)

A

Iron protected by coating it with a layer of zinc
> electroplating or dipping in molten zinc
> ZnCO3 is formed when zinc reacts with O2 and CO2 in air
-> protects the iron by BARRIER METHOD

If coating damaged -> still protected but sacrificial protection

Chemistry Igcse (10 decks)

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