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chemistry > 3.5 Metals > Flashcards

3.5 Metals Flashcards

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1
Q

Metallic Structure

A
  1. A lattice of positive metal ions.
  2. A ‘sea’ of delocalized electrons.
    -The delocalized electrons were lost by the metal ions, and they move freely through the lattice.
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2
Q

Define metallic bonding

A

Metallic bonding is the (strong) electrostatic attraction between the positive metal ions and the negative
delocalized electrons.

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3
Q

Metal properties

A
  1. Metals tend to have high melting points:
    -because the metallic bonding is usually very strong so lots of energy is needed to break it.
  2. Metals conduct electricity:
    -because the delocalized electrons are free to move through the lattice.
  3. Metals are malleable:
    -because the layers of metal ions can slide over each other
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4
Q

Define thermal decomposition

A

A thermal decomposition reaction is when heat energy is used to break down a substance.

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5
Q

Thermal decomposition reaction equation

A

Metal carbonate –> Metal oxide + Carbon dioxide

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6
Q

Thermal decomposition of copper carbonate

A

Copper carbonate (green solid) →Copper oxide (black solid) + Carbon dioxide (colourless gas)

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7
Q

Reactivity series (lowest to highest)

A

Au Ag Cu H Pb Fe Zn C Al Mg Ca Li Na K

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8
Q

Metal + Water reaction

A

Metal + Water → Metal hydroxide + Hydrogen

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9
Q

What are 2 observations of a metal + water reaction? (Magnesium)

A

Magnesium + Water → Magnesium hydroxide + Hydrogen
1. Effervescence - due to the hydrogen gas produced.
2. Solid disappears - due to being used up in the reaction.

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10
Q

What are Group 1 metals called and explain their reactions?

A

-Alkali metals
-React violently with water:
Metal + Water → Metal hydroxide + Hydrogen
-e.g. Lithium + Water → Lithium hydroxide + Hydrogen

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11
Q

What similar observations do the reactions of Li, Na and K with water share?

A

-Solid floats: it is less dense than water.
-Effervescence: hydrogen gas is produced.
-Solid moves: the effervescence propels it around the surface of the water.
-Solid disappears: it is used up in the reaction.

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12
Q

What colour and why does universal indicator turn when added to water after its reaction with a Group 1 metal?

A

-Dark blue

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13
Q

Why are metal hydroxides alkalis?

A

-Because they donate OH:
NaOH –> Na + OH

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14
Q

How do Li, Na & K react with water and what is the trend?

A

-Reactivity increases: reactions become more vigorous
Li: Fast
Na: Faster (Na melts)
K: Fastest (Lilac flame)

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15
Q

Group 1 Metal Reactivity Trend

A

The group 1 metals get more reactive as you go down the group

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16
Q

When a group 1 metal atom reacts, it loses its outer-shell electron to get a full outer shell. This happens more easily why?

A
  1. The atoms get bigger and have more shells
  2. The outer-electron is further from the nucleus
  3. The attraction between the nucleus and the outer-electron is weaker
  4. So less energy is needed to break the attraction
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17
Q

Metal + Steam reaction

A

Metal + Steam → Metal oxide + Hydrogen

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18
Q

Explain the reaction between magnesium and steam?

A

-Magnesium + Water → Magnesium oxide + Hydrogen
-This reaction is usually conducted in a horizontal tube:
-Some wet wool is heated to generate steam for the Mg to react with.
-The H2 gas produced is ignited to safely destroy it.

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19
Q

Why do metals react with cold water and hot steam to produce different products?

A

Steam has more energy, so both bonds in the water molecule can break
e.g. COLD: Hydroxide + Hydrogen
HOT: Oxide + Hydrogen

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20
Q

Acid + Metal reaction

A

Acid + Metal → Salt + Hydrogen

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21
Q

Magnesium + Sulphuric acid reaction

A

-Magnesium + Sulphuric acid → Magnesium sulphate + Hydrogen
-A salt is a compound formed when H is displaced from an acid.
-Mg displaces the H

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22
Q

What are important observations of a acid + metal reaction?

A

e.g. Magnesium + Sulphuric acid
* The metal disappears:
This is because it is used up in the reaction.
* There is fizzing:
This is because a gas (hydrogen) is produced.

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23
Q

The more reactive a metal is, the faster it will react with an acid.
But there are some which we either can’t or won’t use:

A

-LEAST REACTIVE
Au,Ag,Cu
Not possible: Less reactive than H, so can’t displace it
-MIDDLE REACTIVITY
H,Pb, Fe, Zn, C, Al, Mg, Ca
-MOST REACTIVE
Li, Na, K
Not allowed: Reaction with acids is too violent

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24
Q

What is the test for hydrogen?

A

(in a test tube) is:
* Lit splint → squeaky pop!
This is because the combustion of the hydrogen causes the test tube to resonate

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25
Q

Define a displacement reaction

A

More reactive metals can displace less reactive metals from their compounds.

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26
Q

Magnesium + Copper Sulphate reaction

A

-Magnesium can displace copper from copper sulphate
-Magnesium (Grey Solid)+ Copper sulphate (Blue Solid) → Copper (Pink-orange Solid) + Magnesium Sulphate (Colourless solution)

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27
Q

What are observations of displacement reactions?

A

-Solid colour change
-Solution colour change

28
Q

Magnesium + Copper Sulphate reaction observations

A
  1. Solid - turns from grey to pink-orange.
  2. Solution - turns from blue to colourless.
    The non-metal part of the compound (sulphate) remains unchanged.
29
Q

What are the observations for the reaction between Magnesium (grey solid) + Copper sulphate (blue solution) —> Copper (Pink-orange solid) + Magnesium sulphate (colourless solution)

A

Due to the appearances of the particular substances above, the observations would be:
1. Solid - turns from grey to pink-orange.
2. Solution - turns from blue to colourless.
The non-metal part of the compound (sulphate in the above example) remains unchanged.

30
Q

A displacement reaction can only occur when?

A

can only occur if the metal used is more reactive than the metal already in the compound.

31
Q

Reactivity in displacement reactions

A

Zn < X < Mg
* Mg is the most reactive, because it displaced both Zn and X.
* Zn is the least reactive, because it did not displace either Mg or X.
* X is in the middle, because it displaced Zn but not Mg

32
Q

Define an ore

A

A piece of rock that contains metal and other impurities.

33
Q

Which elements from least to most reactive are ores?

A

Au, Ag- Native Ores
Cu,H,Pb,Fe,Zn,C,Al,Mg,Ca,Li,Na,K- Ores
-Gold (Au) and Silver (Ag) too unreactive to have combined with oxygen or sulphur.
-Found ‘native’= chemically uncombined.

34
Q

Why do native metals don’t need to be chemically extracted?

A

They already exist on their own

35
Q

What are methods of chemically extracting metals in ores from their compounds?

A

-Using electricity
-Carbon extraction

36
Q

How is electricity used to chemically extract metal in ores from their compounds?

A

-Metals more reactive than carbon cannot be displaced by carbon.
-Instead, we have to use electricity to break down their ore compounds.
-Aluminium is extracted from its ore in this way

37
Q

How is carbon extraction used to chemically extract metal in ores from their compounds?

A

-Metals less reactive than carbon can be displaced by carbon.
-e.g. Copper can be displaced from its ore (copper oxide) by heating with carbon:
-Carbon + Copper oxide → Carbon dioxide + Copper
C(s) + 2CuO(s) –> CO2(g) + 2Cu(s)
-This only works because carbon is more reactive than copper.

38
Q

Redox reactions (in terms of displacement)

A

Using carbon to displace a metal from its oxide is a redox reaction.

39
Q

Define reduction

A

Loss of oxygen

40
Q

Define reducing agent

A

Takes oxygen away from something else

41
Q

Define oxidation

A

Gain of oxygen

42
Q

Define oxidising agent

A

Gives oxygen to something else

43
Q

Define redox

A

Reduction and oxidation in the same reaction

44
Q

When carbon is used to extract zinc from zinc oxide what is reduced/oxidised?

A

-C + 2ZnO –> CO2 + 2Zn
-Reduced= ZnO loses O
-Reducing agent= C took away O from ZnO
-Oxidised= C gains O
-Oxidising agent= ZnO gives O to C

45
Q

Define rusting

A

Rusting is a chemical process by which iron is oxidized to form rust.

46
Q

What is the chemical name for rust?

A

Hydrated iron(III) oxide:

47
Q

What substances does rusting require?

A

It requires two substances, oxygen + water

48
Q

What are the 2 stages of rusting?

A
  1. Iron is oxidized by oxygen to form iron(III) oxide:
    -4Fe(s) + 3O2(g) → 2Fe2O3(s)
    -Fe has gained oxygen and it has also lost electrons to form Fe3+ ions.
    -For both reasons, it has been oxidized.
  2. Iron(III) oxide is hydrated by water:
    -Fe2O3(s) + xH2O(l) → Fe2O3*xH2O(s)
    -The amount of water gained by the iron(III) oxide varies a lot
49
Q

How can using barriers prevent rusting?

A

-Coating the iron in paint, oil, grease or plastic prevents the iron from coming into contact
with oxygen or water:
-Only works as long as the coating is intact - as soon as it breaks, rusting happens.
-Coating material depending on the use for the iron - oil or grease for moving parts (e.g. bike chains), paint or plastic for larger more stationary objects (e.g. buckets).

50
Q

How does sacrificial protection prevent rusting?

A

-Attach a block of a more reactive metal (e.g. magnesium) to the iron.
-This works by displacing the iron from rust as soon as the rust forms:
-Displacement reaction: Magnesium + Iron(III) oxide → Magnesium oxide + Iron
-The down-side to this method is that the block of magnesium has to be replaced often.

51
Q

What is a disadvantage of sacrificial protection?

A

_The block of magnesium has to be replaced often.

52
Q

How does galvanising prevent rusting?

A

-This method specifically involves coating the iron in zinc.
It works both ways:
* Coating prevents O2 and H2O from coming in contact with the iron…
* but even if a crack appears…
* zinc is more reactive than iron so acts as sacrificial protection as well

53
Q

Define an alloy

A

Alloys are mixtures of a metal with one or more other elements, usually other metals or carbon.

54
Q

What are common known alloys?

A

Steel: Iron + Carbon
Brass: Copper + Zinc
Bronze: Copper + Tin

55
Q

Why are alloys harder than pure metals?

A

-The different-sized atoms/ions prevent the layers of metal ions from sliding over each other.
-This means the alloy is less malleable

56
Q

What is the elements, use and reason of the alloy Iron?

A

ELEMENTS- Fe
USE- Making steel
REASON- Steel is more useful than iron.

57
Q

What is the elements, use and reason of the alloy Low-carbon steel?

A

ELEMENTS- Fe, 0.1% C
USE- Ships, cars, bridges etc.
REASON- Strong, but wow-carbon so can be hammered into various shapes.

58
Q

What is the elements, use and reason of the alloy stainless steel?

A

ELEMENTS- Fe, 1% C, 10% Cr
USE- Cutlery, cooking
utensils, kitchen sinks.
REASON- Cr forms oxide layer that resists
corrosion, so stays shiny and clean.

58
Q

What is the elements, use and reason of the alloy High-carbon steel?

A

ELEMENTS- Fe, 1% C
USE- Tools e.g. knives,
screwdrivers.
REASON- High-carbon so less malleable and stiffer than low-carbon steel.

59
Q

What is the elements, use and reason of the alloy copper?

A

ELEMENTS- Cu
USE- Wires, Cooking pans, Water pipes
REASON- Excellent conductor of electricity.
Excellent conductor of heat. Unreactive and malleable.

60
Q

What is the elements, use and reason of the alloy aluminium?

A

ELEMENTS- Al
USE- Aircraft bodies, Power cables
REASON- Low density and high strength, Low density and conducts

61
Q

How is metal extracted from an ore which contains a metal which is above carbon in the reactivity series?

A

If the ore contains a metal which is above carbon in the reactivity series then ELECTROLYSIS (or a reaction with a more reactive metal) is used to extract the metal

62
Q

What are uses and properties of aluminium?

A

Aircrafts and cans-Low density / resists corrosion
Power cables- Conducts electricity / ductile
Pots and pans-Low density / strong (when alloyed) / good conductor of electricity and heat

63
Q

What are the uses and properties of copper?

A

Electrical wires-very good conductor of electricity and ductile
Pots and pans- very good conductor of heat / very unreactive / malleable
Water pipes- unreactive / malleable
Surfaces in hospitals- antimicrobial properties / malleable

64
Q

What are the uses and properties of of iron?

A

Buildings- Strong
Saucepans- Conducts heat/high melting point/malleable

65
Q

What are the uses and properties of steel?

A

Mild steel- nails, car bodies
High-carbon steel- cutting tools, masonry nails
Stainless steel- cutlery, cooking utensils, kitchen sinks

chemistry (10 decks)

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