What Is Metals? A Visual Guide for OxfordAQA IGCSE Chemistry Students

What Is Metals IGCSE Chemistry Actually Testing?

Think about the things around you right now made of metal: a phone case, a door handle, the pipes carrying water into your home. What is metals igcse chemistry actually testing when it asks about them? Not just "what metals are" in a general sense, but very specific, examinable ideas: why some metals get used for some jobs and not others, how metals get pulled out of rock in the first place, and how chemists rank metals against each other by how readily they react. This guide works through the whole picture that oxfordaqa igcse metals questions draw on, using the same everyday objects you already know to anchor each new idea.

Definition

A metal is an element whose atoms are arranged in a giant structure held together by metallic bonding: positive metal ions surrounded by a "sea" of delocalised electrons that are free to move throughout the structure. This oxfordaqa igcse chemistry definition explains, in one sentence, almost every physical property of metals you are asked about, so it is worth learning precisely rather than approximately.

Key Facts

• Metals conduct heat and electricity well, because the delocalised electrons are free to carry charge and energy through the structure.
• Metals can be bent, hammered or drawn into shape (they are malleable and ductile), because the layers of positive ions can slide over each other without breaking the metallic bonding.
• An alloy is a mixture of at least two elements, at least one of which is a metal, and alloys usually have different, more useful properties than the pure metals they contain.
• Metals can be arranged in a reactivity series, based on how vigorously they react with water and dilute acids.
• The method used to extract a metal from its ore depends on the metal's position relative to carbon in the reactivity series.

Why Metals Behave the Way They Do

Picture the metal atoms in a lump of copper as a stack of oranges in a crate: the oranges (positive ions) sit in a regular, repeating pattern, but unlike a crate of oranges, there is a kind of electron "glue" flowing freely between them, holding the whole stack together while still letting the layers slide past each other under force. That electron glue is exactly what delocalised electrons are, and it is the single idea behind nearly every metallic property on this specification.

• Conduction: because the delocalised electrons can move freely, they can carry an electric current or transfer heat energy through the metal quickly. This is why copper, an excellent conductor, is the standard choice for electrical wiring.
• Malleability and ductility: because the layers of positive ions can slide over each other without breaking the electrostatic attraction to the surrounding electrons, metals can be hammered into sheets or drawn into wires without shattering, unlike a brittle ionic solid.

Metals Explained Through Everyday Uses

Copper is a favourite exam example because its everyday uses map directly onto its properties. Copper is used for electrical wiring and for plumbing pipes because: it is an excellent conductor of both heat and electricity; it is malleable enough to be bent around corners but hard enough to hold its shape as a pipe or tank; and it does not react with water, so it will not corrode away inside a wall or under a floor. Whenever an exam question gives you a use and asks you to explain it, work backwards from the property that use actually depends on, exactly as with copper above.

Alloys extend this everyday-uses idea further. Pure metals are often too soft on their own, so mixing in a second element (or several) changes the properties in a useful direction. Steels, for example, are alloys of iron with carbon and sometimes other metals, and different mixes of steel are chosen for different jobs depending on the properties that composition creates. If a question gives you information about a specific alloy's composition, you are expected to reason about its likely properties and suitable uses from that data, rather than recalling a memorised fact about that particular alloy.

The Reactivity Series

Metals can be arranged in order of reactivity based on how they react (or fail to react) with water and with dilute acids. You should be able to recall and describe the reactions of potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper with water or dilute acid, and use these observations to place the metals in order.

Displacement reactions confirm this ordering experimentally: a more reactive metal will displace a less reactive metal from a solution of its compound. You should be able to describe these displacement reactions in terms of oxidation (loss of electrons) and reduction (gain of electrons), and write the ionic equations for them.

Worked example: iron is added to a solution of copper sulfate. Question: describe and explain what happens, using the terms oxidation and reduction. Answer: iron displaces copper from the solution because iron is more reactive than copper. The iron atoms are oxidised, losing electrons to form iron ions in solution; the copper ions are reduced, gaining electrons to form solid copper, which coats the iron. Ionic equation: Fe(s) + Cu2+(aq) → Fe2+(aq) + Cu(s).

Extracting Metals: The Position in the Series Decides the Method

Unreactive metals such as gold are found in the Earth as the pure element itself, but most metals exist as compounds and require a chemical reaction to extract the pure metal. The extraction method used depends directly on where the metal sits relative to carbon in the reactivity series:

• Less reactive than carbon (for example, iron): the metal can be extracted from its oxide by reduction with carbon. Iron oxide is reduced in the blast furnace to make iron, and you should be able to explain this using the relevant equations, though you do not need to know the full engineering detail of the blast furnace itself.
• More reactive than carbon (for example, aluminium): carbon cannot remove the oxygen from these metal compounds, so electrolysis of the molten compound is used instead. This process uses large amounts of electrical energy, which is why these metals are typically more expensive.

Copper has two additional extraction routes worth knowing beyond the general rule. New, lower-impact methods are being researched to reduce the environmental cost of traditional mining: phytomining uses plants to absorb metal compounds from soil, and the plants are then burned to produce an ash containing the metal compounds; bioleaching uses bacteria to produce a leachate solution containing dissolved metal compounds. Copper can also be obtained from solutions of copper salts either by electrolysis (where you should know the electrode materials and be able to write the ionic half-equations) or by displacement using scrap iron (which you should describe in terms of oxidation and reduction, as in the worked example above).

Recycling

Recycling metals matters because extraction uses limited natural resources and is expensive both in energy terms and in its impact on the environment. You are not required to know the details of any specific recycling process, but you should be able to explain these general benefits clearly when a question asks you to evaluate why recycling a named metal is worthwhile.

Metal Carbonates

The carbonates of magnesium, copper, zinc, calcium and lithium all decompose on heating (thermal decomposition) in a broadly similar way, although not every metal carbonate in Group 1 of the periodic table decomposes at the temperature reached by a standard Bunsen burner, which is a detail worth remembering if a question specifically tests this exception. Metal carbonates also react with acids to produce carbon dioxide gas, a salt, and water, a reaction you should recognise and be able to write a balanced equation for given the names of the reactants.

Self-Check Questions

1. Explain, in terms of structure and bonding, why metals conduct electricity.
2. Explain why copper is a suitable choice of metal for water pipes, linking each use to a specific property.
3. Describe the reaction of iron with copper sulfate solution in terms of oxidation and reduction, and give the ionic equation.
4. Explain why aluminium is extracted by electrolysis rather than by reduction with carbon.
5. Give two reasons why recycling metals is beneficial.
6. State one metal, from the list learned in this unit, that does not decompose readily when heated with a standard Bunsen burner despite generally following the thermal decomposition pattern of metal carbonates.

Once these oxfordaqa igcse chemistry notes have connected metallic bonding to everyday uses, the reactivity series and extraction methods stop being separate facts to memorise and become one connected explanation, which is exactly how oxfordaqa igcse chemistry explained material should feel by the time you reach a past-paper question on it, whether that question is a short recall item or a full extended-response worth several marks.