metals 3.5 Flashcards
what’s the structure of metals?
- a lattice of positive metal ions
- sea of delocalised electrons - lost by metal ions so they move freely through lattice
what’s the definition for metallic bonding?
metallic bonding is the electrostatic attraction between the positive metal ions and the negative delocalized electrons
what types of atoms are involved in metallic bonding?
metal to metal ions
what type of attraction is metallic bonding?
very strong attraction
why do metals tend to have high melting points?
as metallic bonding is very strong and lots of energy is needed to break it
why can metals conduct electricity?
as delocalised electrons are free to move through the lattice
why are metals malleable?
as the layers of metal ions can slide over each other
what’s thermal decomposition?
when heat energy is used to break down a substance
what’s the equation for metal carbonate decomposition?
metal carbonate > metal oxide + carbon dioxide
for example
copper carbonate > copper oxide + carbon dioxide
what’s the colours involved with the decomposition of metal copper carbonate?
copper carbonate (green solid) > copper oxide (black solid) + carbon dioxide (colourless gas)
what’s downwards delievery?
carbon dioxide is denser than air so it is collected in a downwards delivery
as it sinks to the bottom of the tube and stays there until you want to use it
what are the most reactive metals?
K
Na
Li
Ca
Mg
Al
what the reaction of metal and water?
metal + water > metal hydroxide + hydrogen
for example
magnesium + water > magnesium hydroxide + hydrogen
what two observations can be made about the metal + water reaction?
effervescence - due to the hydrogen gas being produced
solid disappears - due to it being used up in the reaction
what are group 1 metals called?
alkali metals
how do group 1 metals react in the metal + water reaction?
react violently with the water
metal + water > metal hydroxide + hydrogen
for example
lithium + water > lithium hydroxide + hydrogen
what’s some of the observations of the group 1 metals and water reaction?
solid floats - less dense than water
effervescence - hydrogen gas in produced
solid moves - effervescence propels it around the surface of water
solid disappears - used up in reaction
what happens if a universal indicator is added to the water after the group 1 metals + water reaction?
turns dark blue as metal hydroxides are alkalis as they donate OH-
what is metal hydroxides?
alkalis
donate OH-
what’s the reactions of Li, Na, K in the group 1 metals + water reaction?
Li - fast
Na - faster, Na melts
K - fastest, K melts, lilac flame
what’s the reactivity trend of group 1 metals?
get more reactive as you go down the group
why do group 1 metals get more reactive as you down the group?
- atoms get bigger and have more shells
- outer shell electron is further from nucleus
- attraction between nucleus and outer shell electron is weaker
- less energy is needed to break the attraction
what the metal + steam reaction?
metal + steam > metal oxide + hydrogen
for example
magnesium + water > magnesium oxide + hydrogen
how is the metal + steam reaction conducted?
in a horizontal tube with wet wool
a metal
causes H2 to become on fire
wet wool is heated to generate steam for metal to react with
H2 gas is ignited to safely destroy it
why do metals react differently with cold water vs hot steam?
steam has more energy so both bonds in the water molecule can break
what’s the metal + acid reaction?
acid + metal > salt + hydrogen
for example
magnesium + sulphuric acid > magnesium sulphate + hydrogen
how is salt formed in an acid + metal reaction?
a H from the acid is displaced
what is the formula for hydrochloric acid?
what salt does it form?
HCl
metal chloride
what is the formula for sulphuric acid?
what salt does it form?
H2SO4
metal sulphate
what is the formula for nitric acid?
what salt does it form?
HNO3
metal nitrate
what is the formula for phosphoric acid?
what salt does it form?
H3PO4
metal phosphate
what’s two observations in the acid + metal reaction?
metal disappears - used up in reaction
fizzing - as the gas hydrogen is produced
what acids can’t you use in an acid + metal?
too reactive : K, Na, Li
unreactive : Au, Ag, Cu
what’s the chemical test for hydrogen?
lit splint > squeaky pop
in a test tube of hydrogen
as the combustion of hydrogen causes test tube to resonate
what’s a metal displacement reaction?
when more reactive metals can displace less reactive metals
for example
magnesium + copper sulphate > copper + magnesium sulphate
what’s the observation for metal displacements?
solid colour change
solution colour change
magnesium (grey solid) + copper sulphate (blue solution) > copper (pink-orange solid) + magnesium sulphate (colourless solution)
ores and natives
what are they?
most metals are found in earth’s crust as compounds with oxygen and sulphur
native metals exist on their own as they are too unreactive to have combined with oxygen or sulphur
using electricity to extract metals in ores:
metals more reactive than carbon cannot be displaced by carbon
so we use electricity
using carbon extraction to extract metals in ores:
metals less reactive than carbon are displaced by carbon
heat up the ore with carbon
what’s a reducing agent?
take away something from something else (this could be oxygen)
what’s an oxidising agent?
gives something to something else (this could be oxygen)
what’s reduction?
the loss of substance
what’s oxidation?
gain of substance
what is rusting?
a chemical process in which iron is oxidised to form rust
what is the chemical name for rust?
hydrated iron(|||) oxide
iron (grey, shiny, malleable)
>
iron (|||) oxide
>
hydrated iron (|||) oxide (brown, dull, brittle)
what two substances does rusting require?
- iron is oxidised by OXYGEN
iron(|||) oxide - hydrated by water
hydrated iron(|||) oxide
what are the methods that prevent rusting?
using barriers
sacrificial protection
galvanising
using barriers to prevent rusting:
coating iron in paint, oil, grease or plastic preventing iron from coming in contact with oxygen or water
works as long as coating is intact
if coating breaks = rusting happens
using sacrificial protection preventing rusting:
attach a block of a more reactive metal to the iron
this works by displacing the iron from rust as soon as rust forms
block of reactive metal (magnesium) has to be replaced often
using galvanising to prevent rusting:
involves coating the iron in zinc
- casting prevents O2 and H2O from coming in contact with iron
- zinc is more reactive than iron so acts as sacrificial protection too
what are alloys?
mixtures of a metal with one or more other elements, usually other metals or carbon
commonly known alloys
steel:
iron + copper
commonly known alloys
brass:
copper + zinc
commonly known alloys
bronze:
copper + tin
why are alloys harder than pure metals?
as they contain different sized ions/atoms preventing the layers of metal ions from sliding over each other
meaning alloy is less malleable
use of iron and elements:
Fe
making steel
- steel is more useful than iron
use of low carbon steel and elements:
Fe and C
ships, cars, bridges etc
- strong
-can be hammered into various shapes
use of high carbon steel and elements:
`Fe and C
tools, knives, screwdrivers etc
- less malleable
-stiff
use of stainless steel and elements:
Fe, C and Cr
cutlery, cooking utensils, kitchen sinks
- Cr forms oxide layer that resists corrosion
- stays shiny and clean
use of copper and elements:
Cu
wires, cooking pan, water pipes
- excellent conductor of electricity
- excellent conductor of heat
- unreactive and malleable
use of aluminium and elements:
Al
aircraft bodies, power cables
- low density and high strength
- low density and conducts
