chemistry metals Flashcards
state of metals
Nearly all metals are solids
Melting point of metals
Most metals have a reasonably high meting point (strong attractions holding
the solid together.
colour of metals
most are a silvery-grey colour
Lustre of metals
metals are shiny when freshly cut
Strength of metals
Most metals have a high tensile strength
malleability of metals
all metals can be worked and shaped.
Ductility of metals
all metals can be stretched out into wires
Conductivity of metals
All metals are good conductors of both heat and electricity
describe transition elements
They have high densities, high melting points and form coloured compounds, and which, as elements and compounds,
often act as catalysts.
Properties of alloys
hardness, toughness, corrosion resistance, magnetizability, and ductility
why alloys are used instead of pure metals
Pure metals are rather soft, ductile and corrosive. Adding other substances can make the pure metal stronger and/or corrosion resistant. This is the advantage of alloys as opposed to pure metals.
do transition elements have variable oxidation states.
yes
what do more reactive metals have a greater tendency to do
More reactive metals have a greater tendency to lose electrons and form positive ions.
what do less reactive metals have a greater tendency to do
The least reactive metals have the greatest tendency to form atoms and therefore their
compounds are less stable.
Mild steel elements and properties
Carbon and iron
Easy to bend and pull into wires
tool steel elements and properties
Tungsten, carbon and iron
Hard, can be heated to high temperatures
Stainless steel elements and properties
Chromium, carbon and iron Hard, does not rust easily
solid pure metal structure
The atoms are arranged in layers. When a force is applied, the layers may slide over each other. The greater the force needed, the harder and stronger the metal.
Why is alloy stronger than pure metal
In a pure metal, the force needed to make the layers slide over each other is small. In an alloy, there are atoms of different sizes. The smaller or bigger atoms distort the
layers of atoms in the pure metal. This means that a greater force is required for the layers to slide over each
other. The alloy is harder and stronger than the pure metal.
properties and uses of aluminium
property: Doesn't react with water Light, strong, conducts well Light, strong, cheap Light, conducts heat well Light, strong, unreactive
Uses: Containers and packaging Long distance wiring Transport vehicles Car engines Buildings (windows etc.)
Property and uses of zinc
property: Reactive
More reactive than iron
Uses: Dry cells
Galvanising
Property and uses of Iron
Properties: Similar expansivity
Strong, cheap
Strong and abundant
Uses: Reinforcing concrete
Nails
Ship building
property and uses of solder
A mixture of 70% Sn and 30 % Pb. Used for joining wires and pipes. Made to give
a low melting point.
Properties and uses of brass
Copper 60-95 % zinc 5-40 %. Used for heat exchangers, screws, zips, jewellery,
hose & pipe fittings, taps, radiator valves. A corrosion resistant alloy.
properties and uses of bronze
Originally meant Cu 90 % Sn 10 % but the term is now much more widely used to
include alloys of aluminium & copper called aluminium bronzes and phosphor
bronzes which are Cu/Sn/P. They are strong and corrosion resistant. Uses include
anything nautical, ornaments, bells and bearings.
Properties and uses of steel
Mixtures of Fe & C but varying amounts are used and other elements are added to
give certain properties.
what is the order of reactivity used for
The order of reactivity is used to predict what will happen when a metal is placed in a solution of a salt of
another metal.
if something that is more reactive is added to something less reactive, it will displace ions of that less reactive thing. But not the other way round
General rule of reactive series
Any metal will displace another metal lower on the reactivity series from a solution of its ions.
(Can only be applied to mg and anything less reactive than mg
What is an ore
An ore is any naturally-occurring source of a metal that you can economically extract the metal from
What is the most common ore
Aluminium
name a rare ore found in high grade ores
Copper
Three examples of oxide ores
Bauxite (Al2O3), Haematite (Fe2O3) or Rutile (TiO2)
Two examples of Sulphide ores
pyrite (FeS2) or Chalcopyrite (CuFeS2)
what does concentrating the ore mean
This simply means getting rid of as much of the unwanted rocky material as possible before the ore is
converted into the metal. In some cases this is done chemically
Froth flotation (method of concentrating ore)
The ore is first crushed and then treated with something which will bind to the particles of the metal
compound that you want and make those particles hydrophobic.
what does hydrophobic mean
“Hydrophobic” literally means “water
fearing”.
What is used for concentrating copper ores
pine oil is often used. The pine oil binds to the copper
compounds, but not to the unwanted rocky material
How is copper ore concentrated after pine oil is added
The treated ore is then put in a large bath of water
containing a foaming agent (a soap or detergent of some kind), and air is blown through the mixture to make
a lot of bubbles. Because they are water-repellent, the coated particles of the metal compound tend to be
picked up by the air bubbles, float to the top of the bath, and are allowed to flow out over the sides. The rest
of the rocky material stays in the bath.
why is metal oxides ore being reduced
the ore is being reduced because oxygen is being
removed.
why is metal sulphides ore being reduced
To a reasonable approximation, you can think of these ores as
containing positive metal ions. To convert them to the metal, you need to add electrons - reduction.
economic factors of reduction
the cost of the reducing agent;
energy costs;
the desired purity of the metal.
Carbon reduction
Carbon (as coke or charcoal) is cheap. It not only acts as a reducing agent, but it also acts as the fuel to
provide heat for the process
Explain reduction by electrolysis
This is a common extraction process for the more reactive metals - for example, for aluminium and metals
above it in the electrochemical series. You may also come across it in other cases such as one method of
extracting copper and in the purification of copper.
During electrolysis, electrons are being added directly to the metal ions at the cathode (the negative
electrode).
a downside is the cost of electricity
The heat source of the blast furnace
The air blown into the bottom of the furnace is heated using the hot waste gases from the top. Heat energy is valuable, and it is important not to waste any. The coke (essentially impure carbon) burns in the blast of hot air to form carbon dioxide - a strongly exothermic reaction. This reaction is the main source of heat in the furnace.
the function of limestone
Iron ore isn’t pure iron oxide - it also contains an assortment of rocky material. This wouldn’t melt at the
temperature of the furnace, and would eventually clog it up. The limestone is added to convert this
into slag which melts and runs to the bottom.
The heat of the furnace decomposes the limestone to give calcium oxide
Cast iron
The molten iron from the bottom of the furnace can be used as cast iron.
Cast iron is very runny when it is molten and doesn’t shrink much when it solidifies. It is therefore ideal for
making castings - hence its name. However, it is very impure, containing about 4% of carbon. This carbon
makes it very hard, but also very brittle. If you hit it hard, it tends to shatter rather than bend or dent.
what is cast iron used for
Cast iron is used for things like manhole covers, cast iron pipes, valves and pump bodies in the water industry,
guttering and drainpipes, cylinder blocks in car engines, Aga-type cookers, and very expensive and very
heavy cookware.
How is steel made
Most of the molten iron from a Blast Furnace is used to make one of a number of types of steel. There isn’t
just one substance called steel - they are a family of alloys of iron with carbon or various metals. Impurities in
the iron from the Blast Furnace include carbon, sulphur, phosphorus and silicon. These have to be removed.
how is sulphur removed from steel
Sulphur has to be removed first in a separate process. Magnesium powder is blown through the molten iron
and the sulphur reacts with it to form magnesium sulphide. This forms a slag on top of the iron and can be
removed.
The still impure molten iron is mixed with scrap iron (from recycling) and oxygen is blown on to the mixture.
The oxygen reacts with the remaining impurities to form various oxides. The carbon forms carbon monoxide.
Since this is a gas it removes itself from the iron! This carbon monoxide can be cleaned and used as a fuel
gas.
How is phosphorus and silicon removed from steel
Elements like phosphorus and silicon react with the oxygen to form acidic oxides. These are removed
using quicklime (calcium oxide) which is added to the furnace during the oxygen blow. They react to form
compounds such as calcium silicate or calcium phosphate which form a slag on top of the iron.
what is galvanising
Galvanising is a method of rust prevention. The iron or steel object is coated in a thin layer of zinc. This stops
oxygen and water reaching the metal underneath - but the zinc also acts as a sacrificial metal. Zinc is more
reactive than iron, so it oxidises in preference to the iron object.
Reactivity series
most reactive: Potassium Sodium Calcium Magnesium Aluminium Carbon Zinc Iron Lead Hydrogen Least reactive: Copper
Should you use the word cloudy
no, use scientific words
