Metals - 3.5 Flashcards
What are the two components of the structure of metal?
- a lattice of positive metal ions
- a ‘sea’ of delocalized electrons
What is metallic bonding?
Metallic bonding is the electrostatic attraction between the positive metal ions and the negative delocalized electrons.
(metallic bonding is usually a very strong attraction)
What are the properties of metal?
- Metals tend to have high melting points:
This is because the metallic bonding is usually very strong so lots of energy is needed to break it. - Metals conduct electricity:
This is because the delocalized electrons are free to move through the lattice - Metals are malleable:
This is because the layers of metal ions can slide over each other.
What is thermal decomposition?
A thermal decomposition reaction is when heat energy is used to break down a substance.
Metal carbonates thermally decompose to form metal oxides and carbon dioxide:
Metal carbonate → Metal oxide + Carbon dioxide
What does the term downward delivery mean?
Carbon dioxide sinks the the bottom of a tube and stays there until you want to use it
What is the order of the metal reactivity series?
Lowest to highest:
Au, Ag, Cu, H, Pb, Fe, Zn, C, Al, Mg, Ca, Li, Na, K
what are two observations that can be made when metals react with cold water?
- effervescence
due to the hydrogen gas produced - solid disappears
due to being used up in the reaction
what are the metals in group one called?
alkali meals - they react violently to form metal hydroxides and hydrogen
What some observations that can be made when group 1 metals react with water?
- 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
What colour does water go after it has reacted with group one metals and universal indicator is added?
dark blue
What happens to the metals in group 1 as they go down the reactivity order?
When a group 1 metal atom reacts, it loses its outer-shell electron to get a full outer shell.
this happens more easily down the group because:
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 weaker
4. so less energy is needed to break the attraction
What is produced when metal and steam reacts?
metal + steam –> metal oxide + hydrogen
How is this reaction conducted?
this reaction is 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.
Why do metals react with cold water and hot steam to produce different products?
Steam has more energy, so both bonds in the water molecule can break
What is produced when acid and metals react?
a salt and hydrogen gas
What salt does hydrochloric acid from?
HCl –> meta chloride (contains Cl-)
What salt does sulphuric acid from?
H2SO4 –> metal sulphate
What salt does nitric acid from?
HNO3 –> Metal nitrate
What salt does phosphoric acid from?
H3PO4 –> Metal phosphate
Which salts are soluble?
sodium - Na +
potassium - K +
ammonium - NH4 +
nitrate NO3-
chloride - Cl- soluble except with
Ag + and Pb 2+
sulphate - SO4 2- soluble except with
Ca 2+, Ba 2+ and Pb 2+
Which salts are insoluble?
Carbonate - CO3 2- except with Na +,
K + and NH4 +
Hydroxide - OH - except with Na +,
K + and Ca 2+
Oxide - O 2- except with Na
+, K + and NH4 +
What are the two important observations that can be made during an acid and metal reaction?
Metal disappears - because it is used up
in the reaction
There is fizzing - because a gas
(hydrogen) is produced
What are the least reactive metals?
Au
Ag
Cu
H
What are the most reactive metals?
Li
Na
K
What is the chemical test for hydrogen?
place a lit splint in a test tube with a gas –> if the gas is hydrogen there will be a squeaky pop
What does the term displacement reaction mean?
More reactive metals can displace less reactive metals from their compounds.
What does a displacement reaction equation look like?
Magnesium + Copper sulphate → Copper + Magnesium sulphate
Mg(s) CuSO4(aq) Cu(s) MgSO4(aq)
Grey solid Blue solution Pink-orange solid Colourless solution
What can you observe from a displacement reaction?
- solid colour change
- solution colour change
What are the two native metals and why?
Gold (Au) and silver (Ag) are too unreactive to have combined with oxygen or sulphur. They are found ‘native’, which means chemically uncombine.
Native metals don’t need to be extracted because they already exist on their own.
How can we extract from Ores?
- Using electricity
- aluminium is extracted from its ore this way - Carbon extraction
- less reactive than carbon so can be displaced
- copper can be displaced from its ore (copper oxide) by heating with carbon
What does the term redox reaction mean?
Using carbon to displace a metal from its oxide is a redox reaction
What are the redox reaction definitions in terms of oxygen?
- Reduction = loss of oxygen
- Reducing agent = takes oxygen away from something else
- Oxidation = gain of oxygen
- Oxidising agent = gives oxygen to something else
- Redox = reduction and oxidation in the same reaction
What is rusting?
Rusting is a chemical process by which iron is oxidized to form rust.
What is the chemical name for rust?
The chemical name for rust is hydrated iron(III) oxide
What two substances does rust require?
- 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. - Iron(III) oxide is hydrated by water:
Fe2O3(s) + xH2O(l) → Fe2O3*xH2O(s)
How can rusting be prevented?
- Using 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 coating is intact - as soon as it breaks, rusting happens - Sacrificial protection:
- 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
- The down-side to this method is that the block of magnesium has to be replaced often - Galvanising:
- This method specifically involves coating the iron in zinc
- 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
What are alloys?
Alloys are mixtures of a metal with one or more other elements, usually other metals or carbon
What are some commonly known alloys?
Steel - iron + carbon
Brass - copper + zinc
Bronze - copper + tin
Why are alloys harder than pure metals?
Because the different-sized atoms/ions prevent the layers of metal ions from sliding over each other. This means the alloy is less malleable
What is irons use?
making steel
–> steel is more useful than iron
What is low-carbon steel’s use?
Ships, cars, bridges etc.
–> Strong, but low-carbon so can be
hammered into various shapes.
What is high-carbon steel’s use?
Tools e.g. knives, screwdrivers
–> High-carbon so less malleable and
stiffer than low-carbon steel
What is stainless steel’s use?
Cutlery, cooking utensils, kitchen sinks
–> Cr forms oxide layer that resists
corrosion, so stays shiny and clean
What is copper’s use?
Wires
–>Excellent conductor of electricity.
Cooking pans
–>Excellent conductor of heat.
Water pipes
–>Unreactive and malleable
What is aluminium’s use?
Aircraft bodies
–>Low-density and high strength.
Power cables
–>Low-density and conducts
