metals Flashcards
structure of a metal?
metals form a metallic lattice made of rows of positive metal ions and delocalised electrons, which are able to move through the structure
why is the melting point of Mg higher than Na
- Na ions have a +1 charge, mg ions have a +2 charge
- the electrostatic attraction between the mg ions and delocalised e- is stronger
- requires more energy to overcome it
why are metals malleable
the rows of positive metal ions can slide over each other and the delocalised electrons are able to maintain the attraction
3.5.2 define the term thermal decomposition
the breaking down of a substance using heat (thermal energy)
define the term ore
a rock containing a metal compound
give one example of a native metal & why it’s found this way
gold/silver - too unreactive to have combined with oxygen or sulfur
how do you know if something is a redox reaction
both oxidation and reduction occur
what does it mean if a substance has been oxidised
it’s lost electrons
what does it mean if a substance is a reducing agent
it’s helped another substance be reduced by giving it electrons
what does it mean if a substance has been reduced
it’s gained electrons
what is the definition of metallic bonding?
the electrostatic attraction between the positive metal ions and the negative delocalised electrons
what are the typical properties of metals?
- high MP: metallic bonding usually very strong, so lots of energy needed to break it
- conduct electricity: bc delocalised e- are free to move
- malleable: bc layers of metal ions can slide over each other
3.5.2 what is the formula for thermal decomposition of metal carbonates?
metal carbonate —> metal oxide + carbon dioxide
what would you observe during the thermal decomposition of copper carbonate?
copper carbonate —> copper oxide + carbon dioxide: green solid —> black solid + colourless gas
3.5.2 what is downward delivery?
CO2 denser than air, so often collected using this method. that means it just sinks to bottom of a tube & stays there until it needs to be used
3.5.3 what is the order of the metal reactivity series, from lowest to highest?
Au Ag Cu H Pb Fe Zn C Al Mg Ca Li Na K
(H and C non-metals but they’re included bc positions important when considering displacement reactions
3.5.3 what is the general formula for metals reacting with cold water?
metal + water —> metal hydroxide + hydrogen
3.5.3 what are the observations for the reaction between magnesium and water?
- effervescence - due to H gas produced
- solid disappears - due to being used up in reaction
3.5.3 what happens with metals less reactive than Mg for the metal + water reaction?
they react so slowly with cold water that you can’t actually tell anything’s happening; even with Mg need to wait few mins
3.5.3 what are the metals in group 1 called, & what do they do?
the alkali metals; react violently w water to form metal hydroxides & hydrogen
3.5.3 what are the shared observations for the reaction of Li, Na and K with water?
- solid floats - it’s less dense than water
- effervescence - hydrogen gas produced
- solid moves - effervescence propels it around surface of water
- solid disappears - used up in reaction
- when universal indicator added to water afterwards it turns dark blue
3.5.3 what do you observe when Na is reacted with water?
faster than Li, and Na melts
3.5.3 what happens when you react K with water?
- fastest
- K melts
- lilac flame
3.5.3 what happens to the reactivity of the group 1 metals as you go down the group?
increases
3.5.3 why does the reactivity increase as you go down the group 1 metals?
- atoms get bigger & have more shells
- outer electron further from nucleus
- attraction between nucleus & outer electron is weaker
- so less energy needed to break the attraction
3.5.3 what is the formula for metal reacting with steam?
metal + steam —> metal oxide + hydrogen
3.5.3 describe how to conduct an experiment for the reaction between metal and steam
- put some wet wool and a Mg ribbon into a horizontal test tube, with a bung on the top and a thingy coming out of the bung
- heat the test tube: some wet wool is heated to generate steam for the Mg to react with
- ignite the H2 gas coming out the test tube to safely destroy it
3.5.3 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 - forming just a metal oxide and a H2, not a metal hydroxide and an H
3.5.4 what is the formula for an acid reacting with a metal?
acid + metal —> salt + hydrogen
what salts are always soluble?
Na+, K+, NH ₄+, NO ₃-
is Cl- soluble?
yes, except with Ag+ and Pb2+
is SO ₄2- soluble?
yes, except with Ca2+, Ba2+ and Pb2+
is CO ₃2- soluble?
no, except with Na+, K+ and NH ₄+
is OH- soluble?
no, except with Na+, K+ and Ca2+
is O2- soluble?
no, except with Na+, K+, and NH ₄+
3.5.4 what are the two important observations in an acid + metal reaction?
- metal disappears because used up in reaction
- fizzing because gas (H) produced
3.5.4 what metals cant/won’t react with H and why?
- Au, Ag and Cu, because they’re less reactive than H so won’t displace it
- Li, Na and K, because they’re too reactive so reaction with acids is too violent
3.5.5 what are the observations for displacement reactions?
- solid colour change
- solution colour change
3.5.6 what are ores?
the rocks containing specific metal compounds
3.5.6 what are most metals in the earths crust found as?
found as compounds with oxygen & sulphur, bc over a long time those metals have reacted w oxygen & sulphur
3.5.6 which metals are found ‘native’ in the earth’s crust and why?
gold (au) and silver (ag) - too unreactive to have combined with oxygen or sulphur
3.5.6 what does ‘native’ mean for metals?
means chemically uncombined
3.5.6 do native metals need to be chemically extracted?
no they already exist on their own
3.5.6 how is the method of extraction for metals chosen?
it depends on how reactive the metal is
3.5.6 what is the electricity method of chemical extraction? (electrolysis)
- metals more reactive than carbon can’t be displaced by carbon
- instead, have to use electricity to break down their ore compounds
- don’t need to know how this works
3.5.6 what is the carbon extraction method of chemical extraction?
- metals less reaction than carbon can be displaced by carbon
- for example, copper can be displaced from its ore (copper oxide) by heating with carbon:
carbon C (s) + copper oxide 2CuO (s) —> carbon dioxide CO2 (g) + copper 2Cu (s) - only works bc carbon more reactive than copper
3.5.6 what type of reaction is using carbon to displace a metal from its oxide?
a redox reaction
3.5.7 what are the qualities of iron compared to hydrated iron (III) oxide (rust)?
iron: grey shiny malleable
rust: brown dull brittle
3.5.7 what two stages does rusting occur in?
-
iron oxidised by oxygen to form iron(iii) oxide:
4Fe (s) + 3O2 (g) —> 2Fe2O3 (s)
Fe has gained oxygen and also lost e- to form Fe3+ ions. for both reasons, it’s been oxidised
-
iron(iii) oxide hydrated by water:
Fe2O3 (s) + xH2O (l) —> Fe2O3•xH2O (s)
the amount of water gained by iron(iii) oxide varies a lot
3.5.7 what elements are in steel, brass, and bronze?
steel: iron + carbon
brass: copper + zinc
bronze: copper + tin
3.5.7 what is the use for iron (alloys)?
making steel - steel more useful than iron
3.5.7 what elements are in low-carbon steel, and what are its uses?
Fe, 0.1% C; ships, cars bridges etc - strong, but low-carbon so can be hammered into various shapes
3.5.7 what elements are in high-carbon steel, and what are its uses?
Fe, 1% C; tools e.g. knives, screwdrivers - high-carbon so less malleable & stiffer than low-carbon steel
3.5.7 what elements are in stainless steel, and what are its uses?
Fe, 1% C, 10% Cr; cutlery, cooking utensils, kitchen sinks - Cr forms oxide layer that resists corrosion, so stays shiny & clean
3.5.7 what are coppers uses? (alloys)
- wires: excellent conductor of electricity
- cooking pans: excellent conductor of heat
- water pipes: unreactive & malleable
3.5.7 what are the uses for aluminium (alloys)?
- aircraft bodies: low-density & high strength
- power cables: low-density & conducts
