IGCSE Chemistry > Metals - 3rd > Flashcards

Metals - 3rd Flashcards

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1
Q

what is the structure of a metal?

A

metallic structure has two components:
- a lattice of positive metal ions
- a ‘sea’ of delocalised electrons
the metal ions each have their usual charges, so zinc ions are Zn 2+, sodium atoms are Na + , etc
- the delocalised electrons were lost by the metal ions, and they move freely through the lattice
metals: picture 1

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2
Q

what is metallic bonding?

A

metallic bonding is the electrostatic attraction between the positive metal ions and the negative delocalised electrons. it can be thought of as the delocalised electrons ‘gluing’ the metal ions together

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3
Q

how strong is metallic bonding?

A

metallic bonding is usually a very strong attraction.

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4
Q

what are the properties of metals?

A
  • metals tend to have high melting points
  • metals conduct electricity
  • metals are malleable
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5
Q

why do metals tend to have high melting points?

A

as the metallic bonding is usually very strong, so lots of energy is needed to break it.

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6
Q

why do metals conduct electricity?

A

because the delocalised electrons are free to move through the lattice.

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7
Q

why are metals malleable?

A

as the layers of metal ions can slide over each other.

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8
Q

what is thermal decomposition reaction?

A

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

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9
Q

what do metal carbonates decompose to?

A

they decompose to form metal oxides and carbon dioxide.

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10
Q

what is downward delivery?

A

Carbon dioxide is denser than air, so it is often collected by downward delivery. this means it just sinks to the bottom of a tube and stays there until you want to use it.

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11
Q

what is the metal reactivity series?

A

some metals are more reactive than others. we see this on the reactivity series:
metals: picture 2

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12
Q

why are hydrogen and copper included on the reactivity series?

A

they are non-metals, but they are included because their positions are important when considering displacement reactions.

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13
Q

what are metal and water reactions?

A

metal + water -> metal hydroxide + hydrogen

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14
Q

what are two significant observations of a metal and water reaction?

A
  • effervescence : hydrogen gas produced
  • solid disappears : due to being used up in the reaction.
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15
Q

how do metals react in metal and water reactions?

A

the metals which are less reactive than magnesium react so slowly with cold water that you can’t actually tell anything is happening.

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16
Q

how do metals in group one react in metal and water reactions?

A

they react with water to form metal hydroxides and hydrogen:
metal + water -> metal hydroxide + hydrogen

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17
Q

which metals in group one react similarly?

A
  • the reactions of Li, Na, K with water share some similar observations:
  • solid floats as it is less dense than water
  • effervescence - hydrogen gas is produced
  • solid moves - effervescence propels it around the surface of the water
  • solid disappears - it is used in the reaction
  • metal hydroxides are alkaline because they donate OH- : NaOH -> Na+ + OH-
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18
Q

What is observed when the universal indicator is added to the water of a metal and water reaction?

A
  • it turns dark blue
  • the metal hydroxides are alkalis because they donate OH-
  • as the metal gets more reactive, the reactions become more vigorous
  • this results in some extra observations for Na and K compared to Li.
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19
Q

What is the reactivity of Lithium, sodium and potassium?

A

Li- Fast
Na- Faster as it melts
K- fastest as it melts and we can see a lilac flame.

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20
Q

What is the relation between the group 1 metals and reactivity?

A

The group 1 metals get more reactive as you go down the group as when a group 1 atom reacts, it loses its outer-shell electron to get a full outer-shell.
This happens more easily down the group because:
- the atoms get bigger and have more shells
- the outer-electron is further from the nucleus
- the attraction between the nucleus and the outer-electron is weaker
- so less energy is needed to break the attraction.

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21
Q

What do metal and steam reactants produce?

A

Metal + steam -> metal oxide + hydrogen

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22
Q

Where is the metal and steam reaction usually conducted?

A

In a horizontal tube.
metals : picture 1

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23
Q

Explain the process of the experiment of the metal and steam reaction.

A
  • 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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24
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.

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25
How do acids react with metals?
Acids react with metals to form a salt and hydrogen gas: Acid + metal -> salt + hydrogen
26
When is a salt compound formed?
When H is displaced from an acid. E.g. in Mg + H2SO4 -> H2 + MgSO4 , the Mg displaces the H as it is more reactive.
27
What is the name of the salt produced with: - hydrochloric acid - sulphuric acid - nitric acid - phosphoric acid
- metal chloride - metal sulphate - metal nitrate - metal phosphate
28
How can you find out if a salt is soluble?
Look up its ions in the solubility rules.
29
What are the 2 important observations in an acid and metal reaction?
- the metal disappears as it is used up in the reaction - there is fizzing as a gas (hydrogen) is produced
30
What is the correlation between the reactivity of a metal and how it will react with an acid?
The more reactive a metal is, the faster it will react with an acid, however, there are some which we either can’t or won’t use. This is because it will not be able to displace with Hydrogen as it might be less reactive than Hydrogen, like Au, Ag and Cu.
31
What is the chemical test for hydrogen?
The chemical test for Hydrogen in a test tube is : - lit splint -> squeaky pop! This is because the combustion of hydrogen causes the test tube to resonate.
32
What is a displacement reaction?
Most reactive metals can displace less reactive metals from their compounds.
33
What are observations for displacement reactions?
Observations for these reactions vary a lot, but there are always two to think about: - solid colour change - solution colour change The non-metal part of the compound (sulphate in the above example) remains unchanged.
34
When can a displacement reaction occur?
A displacement reaction can only occur if the metal used is more reactive than the metal already in the compound
35
What are most metals found as?
- most metals are found in the Earth’s crust as compounds with oxygen and sulphur. This is because over a long time those metals have reacted with oxygen and sulphur. The rocks containing specific metal compounds are called ores.
36
Which metals are found native?
Gold and silver are too unreactive to have combined with oxygen or sulphur. They are found native, which means chemically uncombined.
37
Do native metals need to be extracted?
No, they do not need to be chemically extracted because they already exist on their own.
38
Do metals in ores need to be extracted?
Yes, metals in ores need to be chemically extracted from their compounds.
39
How are metals in ores chemically extracted from their compounds?
1. Using electricity: 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 *metals: picture 2* 2. Carbon extraction: Metals less reactive than carbon can be displaced by carbon. For example, copper can be displaced from its ore (copper oxide) by heating with carbon. This only works because carbon is more reactive than copper. *metals: picture 3*
40
What is a redox reaction?
Using carbon to displace a metal from its oxide is a redox reaction.
41
What is the definition of reduction in terms of oxygen?
Loss of oxygen
42
What is the definition of reducing agent in terms of oxygen?
Takes oxygen away from something else
43
What is the definition of oxidation in terms of oxygen?
Gain of oxygen
44
What is the definition of oxidising agent in terms of oxygen?
Gives oxygen to something else
45
What is the definition of redox in terms of oxygen?
Reduction and oxidation in the same reaction.
46
What is rusting?
Rusting is a chemical process by which iron is oxidised to form rust.
47
what is the chemical name for rust?
Hydrated iron (III) oxide
48
what does the iron require to rust?
- oxygen (o2) - water (H20)
49
Explain the process of rusting?
1. Iron is oxidised by oxygen to form iron oxide - iron has gained oxygen and it has also lost electrons to form Fe 3+ ions 2. Iron oxide is hydrated by water - the amount of water gained by the iron oxide varies a lot
50
What are alloys?
Alloys are mixtures of a metal with one or more other elements, usually other metals or carbon.
51
How can rusting be prevented?
- using barriers - sacrificial protection - galvanising
52
Explain how rusting can be prevented through barriers?
- coating the iron in paint, oil, grease or plastic prevents the iron from coming into contact with oxygen or water. - this only works as long as the the coating is intact - as soon as it breaks, rusting happens. - you can choose the 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)
53
Explain how rusting can be prevented through sacrificial protection?
- attach a block of a more reactive metal (e.g. magnesium) to the iron - this works by displacing the iron from the rust as soon as the rust forms - the down side to this method is that the block of magnesium has to be replaced often.
54
Explain how rusting can be prevented through galvanising.
- 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.
55
Name some commonly known alloys.
- steel : iron + carbon - brass : copper + zinc - bronze : copper + tin
56
Why are alloys harder than pure metals?
- the different-sized atoms/ions prevent the layers of metal ions from sliding over each other, which means that the alloy is less malleable.
57
What is steel?
- a very important alloy composed. Of iron with small quantities of carbon. - there are different types of steel depending on the amount of carbon.
58
What is iron used for and why?
- Fe - Making steel - steel is more useful than iron
59
What is low-carbon steel used for and why?
- Fe + 0.1% C - ships, cars, bridges, etc - because it is strong, but wow-carbon so can be hammered into various shapes.
60
What is high-carbon steel used for and why?
- Fe + 1% C - tools e.g. knives, screwdrivers - because it is high carbon so less malleable and stiffer than low-carbon steel
61
What is stainless steel used for and why?
- Fe + 1% C + 10% Cr - cutlery, cooking utensils, kitchen sinks - because Cr forms oxide layer that resists corrosion, so stays shiny and clean
62
What is copper used for and why?
- Cu - wires, cooking pans, water pipes - because it is an excellent conductor of electricity and an excellent conductor of heat and is unreactive and malleable
63
what is aluminium used for and why?
- Al - aircraft bodies and power cables - because it has low density and high strength and conducts.
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