Chapter 9 Flashcards
Propertiesnof metals (the properties of metals are due to metallic bonding)
- conduct heat and electricity
- malleable (can be hammered and made into different shapes) + ductile (can be drawn into wires)
- High-density + high melting points
Properties of non metals
- Don’t conduct heat and electricty
- Brittle when solid
- Low melting points
Chemical properties of metals -> reactivity with cold water
reactivity with cold water: forms metal hydroxide and hydrogen gas
. Includes: metals above and including magnesium -> metals like potassium, sodium and calcium react vigorously with water
Chemical properties of metals -> reactivity with steam
Reactivity with steam: forms of metal oxide and hydrogen -> more reactive metal = faster reaction
. Includes: metals under magnesium and above, including iron
Chemical properties of metals -> reactivity with dilute acid
Reactivity with dilute acid: forms, salt and hydrogen gas -> more reactive metal = faster reaction with acid
. Includes: metals above copper
Chemical properties of metals -> reactivity with oxygen
Reactivity with oxygen: forms a metal oxide
. Includes: metals above, and including copper
Chemical properties of metals -> aluminium
. Aluminium: doesn’t react with water or dilute acids -> surface of aluminium reacts with oxygen in air to form a layer of unreactive aluminium oxide which acts as a barrier against further oxidation
Uses of metals: aluminium -> aircraft manufacture
Most important property
. High strength
. Low density
Uses of metals: aluminium -> overhead power cables manufacture
Most important property
. Low density
. Good electrical conductor
Uses of metals: aluminium -> food containers
Most important property
. Resistant to corrosion.
Uses of metals: copper
Electrical wires
. Good electrical conductor
. Ductile
Alloys
Alloys: mixture of a metal with other element -> can be harder and stronger than pure metals + more useful
-> alloys contains atom of different sizes, distorting the normal regular arrangement of atoms in metals -> harder for layers to slide over each other
Common alloys: brass
Mixture of copper and zinc
Common alloys: stainless steel
Mixture of iron and other elements (nickel, chromium and carbon) -> used in cutlery due to its hardness and resistance to resting
Displacement reactions
More reactive metals displace less reactive metals -> reactive metals easily lose electrons to form cations (less reactive metals don’t give up electrons to form cations as easily)
. Reactive metal = reducing agent
Corrosion of metals: corrosion of iron and steel
. Iron and steel corrode easily to make rust (hydrated iron (III) oxide) -> only happens in the presence of both oxygen and water
Corrosion of metals: corrosion of iron and steel -> preventing rusting of iron
. Barrier methods: prevent rusting by excluding oxygen or water
- Painting
- Greasing
- Coating with plastic
. Sacrificial protection: placing a more reactive metal with iron -> water and oxygen react with this sacrificial metal instead of with iron as it loses electrons more easily than iron to form cations
-> zinc: often used in sacrificial protection -> coating of zinc is called galvanizing
Extraction of metals
Extraction of metals from its ore (metal oxide) always involves the reduction of the metal
. More reactive metal = harder to extract from or ore
- reduction with carbon: heating or with carbon or carbon monoxide
Extraction of iron
. Iron ore: Hematite
. The blast furnace -> reduction by carbon
Extraction of aluminium by electrolysis
. Aluminium ore: bauxite
. Aluminium oxide is dissolved in molten cryolite -> lower is melting point (less energy -> reduces cost) + increases electrical conductivity
-> anode needs to be replaced regularly as oxygen reacts with the graphite anodes (carbon) to produce carbon dioxide due to high temperatures -> anode erodes + shrinks
