chem 13.5 Flashcards
(48 cards)
define an alloy
a mixture of a metal and one / few other elements
what makes a metal easily malleable / ductile
as metals are held together by non-directional metallic bonds, atoms can move around each other easily without breaking the bond. as a result, metals are malleable / ductile
how are alloys usually made
by heating the metal and the other elements together, allowing them to melt and mix
how different are the physical properties of an alloy compared to a pure metal element
the alloy becomes less malleable / ductile ++ also becomes harder as mixtures have an irregular structure (as the solute hinders the movement of the metal atoms, so they cannot move around easily)
how do the properties of an alloy compare to that of its constituent metals
alloys usually have more useful properties that any one of the constituent metals
composition, properties, uses of steel
composition: ~95% iron, ~5% carbon
properties: stronger and harder than iron
uses: widely used as frames of many buildings / in construction of bridges
composition, properties, uses of stainless steel
composition: 70% iron, 20% chromium, 9.5% nickel, 0.5% carbon
properties: stronger, more resistant to corrosion than iron
uses: widely used in making cooking utensils / tableware / surgical tools
composition, properties, uses of carbon steel
composition: 99.8% iron, 0.2% carbon
properties: stronger, more resistant to corrosion than iron
uses: making motor car bodies / construction materials
composition, properties, uses of titanium alloy
composition: 90% titanium, 6% aluminium, 4% vanadium
properties: very strong, low density
uses: making aircraft bodies / spacecraft bodies / glasses frames
composition, properties, uses of bronze
composition: 90% copper, 10% tin
properties: harder than copper / tin, more resistant to corrosion
uses: making statues
composition, properties, uses of duralumin
composition: 95% aluminium, 3% copper, 1% magnesium / manganese
properties: stronger than aluminium, low density
uses: building aircraft bodies
composition, properties, uses of brass
composition: 70% copper, 30% zinc
properties: harder than copper / zinc, more resistant to corrosion
uses: making musical instruments / doorknobs / keys
composition, properties, uses of coinage metals
composition: copper, zinc, tin, nickel in different proportions
properties: harder and shinier than pure gold + resistant to corrosion
uses: making coins
composition, properties, uses of carat gold
composition: gold (major component), silver / copper (in different proportions)
properties: harder + shinier than pure gold
uses: making ornaments / coins
composition, properties, uses of solder
composition: 50% tin, 50% lead
properties: has a lower melting point than tin / lead, but harder than tin / lead
uses: for joining electronic parts in circuit boards
what is crude oil used for
to make fuels (eg. petrol / lpg), plastics
what is crude oil like and what is it composed of
a thick black liquid with a pungent odour (also known as petroleum)
a mixture of many different hydrocarbons
what are hydrocarbons
a compound composed of carbon and hydrogen atoms only (but different molecules have different numbers of each atom, and as a result are of different sizes)
4 smallest hydrocarbons + hydrocarbon molecule formula
methane (CH4)
ethane (C2H6)
propane (C3H8)
butane (C4H10)
C(n) H(n+2)
why can’t crude oil be directly ne used as a fuel
a lot of black smoke (soot) / harmful gases (carbon monoxide) are produced when crude oil is burnt directly
what controls a hydrocarbon’s properties
its molecular size
what parameter can hydrocarbons be separated by and how can they be separated
boiling point, can be separated through a refining process called fractional distillation
what is a fraction
a mixture of hydrocarbons with small differences in their boiling pts
fractional distillation exp: procedure
- put some glass wool into a boiling tube and then add about 5cm3 of crude oil to the boiling tube (make sure the glass wool is soaked w crude oil)
- heat the crude oil gently; move the flame backwards and forwards so that the crude oil is heated uniformly
- collect the distillate with a boiling point range from room temperature to 100C. remove and stopper the test tube, labelling it ‘1’ and setting it on the test tube rack
- heat the remaining crude oil more strongly. use another test tube to collect the second fraction with a boiling point range from 100-150C. remove the test tube and stopper it. label it ‘2’ and put it on the rack.
- repeat step 5 to collect the third fraction (150-200C) and the fourth fraction (200-250C)
- turn off the bunsen burner
