Properties of metals

1. Overview

Metals occupy the left and center of the Periodic Table and account for about 80% of all elements. Understanding their physical and chemical properties is essential for determining their uses in construction, electronics, and industry, as well as predicting how they react with the environment.

Key Definitions

• Malleable: Capable of being hammered or pressed into thin sheets without breaking.
• Ductile: Capable of being drawn out into thin wires.
• Thermal Conductor: A material that allows heat to pass through it easily.
• Electrical Conductor: A material that allows an electric current to flow through it.
• Lustrous: Having a shiny or reflective surface (when freshly cut or polished).
• Sonorous: Making a deep, ringing sound when struck.

Core Content

A. Physical Properties: Metals vs. Non-Metals

Metals and non-metals show distinct physical differences based on their atomic structures.

Property	Metals	Non-Metals
Thermal Conductivity	Good conductors	Poor conductors (insulators)
Electrical Conductivity	Good conductors (due to mobile electrons)	Poor conductors (except graphite)
Malleability/Ductility	Malleable and ductile	Brittle (shatter when struck)
Melting/Boiling Points	Generally high	Generally low
Appearance	Shiny (lustrous)	Dull
Density	Usually high density	Usually low density

B. Chemical Properties of Metals

Metals tend to lose electrons to form positive ions (cations). Their reactivity varies depending on their position in the reactivity series.

1. Reaction with Dilute Acids Most metals react with dilute acids to produce a salt and hydrogen gas.

• Word Equation: Metal + Acid → Salt + Hydrogen gas
• Symbol Equation: $Mg(s) + 2HCl(aq) \rightarrow MgCl_2(aq) + H_2(g)$

2. Reaction with Cold Water Very reactive metals (like Group I) react with cold water to form a metal hydroxide and hydrogen gas.

• Word Equation: Metal + Water → Metal Hydroxide + Hydrogen gas
• Symbol Equation: $2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g)$

3. Reaction with Steam Less reactive metals (like Magnesium or Zinc) do not react easily with cold water but will react with steam to form a metal oxide and hydrogen gas.

• Word Equation: Metal + Steam → Metal Oxide + Hydrogen gas
• Symbol Equation: $Mg(s) + H_2O(g) \rightarrow MgO(s) + H_2(g)$

4. Reaction with Oxygen Metals react with oxygen to form metal oxides. This is often an oxidation reaction.

• Word Equation: Metal + Oxygen → Metal Oxide
• Symbol Equation: $4Li(s) + O_2(g) \rightarrow 2Li_2O(s)$
• Symbol Equation: $2Mg(s) + O_2(g) \rightarrow 2MgO(s)$

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Extended Content (Extended Only)

There is no specific extended curriculum content for this sub-topic (9.1) beyond the core requirements.

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Key Equations

Reaction Type	General Equation	Example with State Symbols
Metal + Acid	$M + HX \rightarrow Salt + H_2$	$Zn(s) + H_2SO_4(aq) \rightarrow ZnSO_4(aq) + H_2(g)$
Metal + Water	$M + H_2O \rightarrow M(OH)_n + H_2$	$Ca(s) + 2H_2O(l) \rightarrow Ca(OH)_2(aq) + H_2(g)$
Metal + Steam	$M + H_2O \rightarrow MO + H_2$	$Zn(s) + H_2O(g) \rightarrow ZnO(s) + H_2(g)$
Metal + Oxygen	$M + O_2 \rightarrow MO$	$2Cu(s) + O_2(g) \rightarrow 2CuO(s)$

• Symbols: $s$ = solid, $l$ = liquid, $g$ = gas, $aq$ = aqueous (dissolved in water).

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Common Mistakes to Avoid

• ❌ Wrong: Stating that metals react with water to form oxides.
• ✓ Right: Metals react with cold water to form hydroxides, but react with steam to form oxides.
• ❌ Wrong: Writing hydrogen as $H$ in equations.
• ✓ Right: Hydrogen is a diatomic molecule; always write it as $H_2(g)$.
• ❌ Wrong: Forgetting state symbols when requested.
• ✓ Right: Always include $(s), (l), (g),$ or $(aq)$ to describe the physical state of each substance.

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Exam Tips

• Command Words:
  • "State": Give a brief fact (e.g., "State two physical properties of metals" → High melting point and good electrical conductivity).
  • "Explain": You must give a reason. If asked why metals conduct electricity, mention "delocalized electrons that are free to move."
  • "Name": Give the specific chemical name (e.g., "Name the gas produced" → Hydrogen).
• Question Types: Expect questions where you are given an "unknown element X" and its properties (e.g., it is brittle and a poor conductor). You will be asked to identify it as a non-metal.
• Real-world Contexts: Exams often ask why Copper is used for wiring (ductility and electrical conductivity) or why Aluminum is used for pans (thermal conductivity).
• Key Identification: If a question mentions a "gas that pops with a lighted splint," it is identifying Hydrogen ($H_2$) produced from a metal reacting with acid or water.

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Exam-Style Questions

Practice these original exam-style questions to test your understanding. Each question mirrors the style, structure, and mark allocation of real Cambridge 0620 Theory papers.

Exam-Style Question 1 — Short Answer [5 marks]

Question:

A student investigates the reaction of different metals with dilute hydrochloric acid. She places small pieces of magnesium, zinc, and copper separately into test tubes containing equal volumes and concentrations of hydrochloric acid.

(a) State two observations she would make in the test tube containing magnesium that would indicate a chemical reaction is occurring. [2]

(b) State one observation she would make in the test tube containing copper. Explain your answer. [3]

Worked Solution:

(a)

1. Effervescence/Bubbles/Gas produced The magnesium reacts with the hydrochloric acid to produce hydrogen gas, which is observed as bubbles. Award one mark for stating effervescence, bubbles or gas produced.

2. Magnesium disappears / Magnesium gets smaller The magnesium is reacting and forming magnesium chloride, causing the solid metal to decrease in size. Award one mark for stating the magnesium disappears or gets smaller.

How to earn full marks:

• State 'effervescence' or 'bubbles' or 'gas produced' for the first mark.
• State 'magnesium disappears' or 'magnesium gets smaller' for the second mark.

(b)

1. No reaction / No bubbles / No change Copper is less reactive than hydrogen and therefore does not react with dilute hydrochloric acid. Award one mark for stating no reaction or no bubbles or no change.

2. Copper is less reactive than hydrogen. This explains why copper does not displace hydrogen from the acid. Award one mark for stating that copper is less reactive than hydrogen.

3. Therefore, no hydrogen gas is produced. This links the lack of reactivity to the absence of observable bubbles. Award one mark for stating that no hydrogen gas is produced.

How to earn full marks:

• State 'no reaction' or equivalent for the first mark.
• State that copper is less reactive than hydrogen for the second mark.
• State that no hydrogen gas is produced because of copper's lack of reactivity for the third mark.

Common Pitfall: When describing observations, be specific. Saying "a reaction occurs" is too vague. You need to describe what you would actually see, such as bubbles forming or the metal disappearing. Also, make sure your explanation in part (b) directly relates to the observation you made.

Exam-Style Question 2 — Short Answer [6 marks]

Question:

Metals have various physical properties that make them useful for different applications.

(a) State two physical properties of metals, other than their ability to conduct electricity. [2]

(b) Explain why metals are good conductors of electricity. [2]

(c) State two uses of metals that rely on their malleability. [2]

Worked Solution:

(a)

1. High melting point Most metals have strong metallic bonds, requiring a lot of energy to break. Award one mark for stating 'high melting point'.

2. Malleable/Ductile/Strong/Shiny/Sonorous/High density These are all characteristic physical properties of metals. Award one mark for stating any one of these properties.

How to earn full marks:

• State 'high melting point' for the first mark.
• State any other valid physical property of metals for the second mark.

(b)

1. Metals have delocalised electrons. The electrons are not bound to individual atoms. Award one mark for stating that metals have delocalised electrons.

2. These delocalised electrons are free to move and carry charge. The movement of these electrons constitutes an electric current. Award one mark for stating that delocalised electrons are free to move.

How to earn full marks:

• State that metals have delocalised electrons for the first mark.
• State that these electrons are free to move and carry charge for the second mark.

(c)

1. Making car body panels. Malleability allows metals to be hammered or pressed into shape. Award one mark for stating making car body panels.

2. Making jewellery. Metals can be shaped into intricate designs. Award one mark for stating making jewellery.

How to earn full marks:

• State making car body panels for the first mark.
• State making jewellery for the second mark.
• Accept other valid uses of malleable metals such as making coins.

Common Pitfall: Remember that conductivity (both electrical and thermal) counts as ONE physical property. So, if the question asks for properties other than electrical conductivity, don't mention thermal conductivity. Also, be sure to link the use of a metal to its malleability in part (c).

Exam-Style Question 3 — Extended Response [9 marks]

Question:

Iron is a commonly used metal. However, it is susceptible to corrosion, forming rust.

(a) State the chemical name and formula of rust. [2]

(b) Describe two methods used to prevent iron from rusting. For each method, explain how it works. [4]

(c) A student investigates the rate of rusting of iron nails under different conditions. She places four iron nails in separate test tubes as follows:

• Test tube 1: Nail completely submerged in distilled water.
• Test tube 2: Nail completely submerged in distilled water that has been boiled to remove dissolved air. A layer of oil is added on top of the water.
• Test tube 3: Nail placed in a desiccator containing anhydrous calcium chloride.
• Test tube 4: Nail in contact with a more reactive metal (zinc) and submerged in distilled water.

After one week, she observes the nails and records her observations. Predict the order of the test tubes (1-4) in terms of the amount of rust formed, from most rust to least rust. Explain your reasoning. [3]

Worked Solution:

(a)

1. Hydrated iron(III) oxide This is the correct chemical name for rust. Award one mark for stating 'hydrated iron(III) oxide'.

2. Fe$_2$O$_3$.xH$_2$O This is the correct formula for rust, showing it is a hydrated form of iron(III) oxide. Award one mark for stating 'Fe$_2$O$_3$.xH$_2$O'. Accept Fe$_2$O$_3$.nH$_2$O.

How to earn full marks:

• State 'hydrated iron(III) oxide' for the first mark.
• State the correct formula 'Fe$_2$O$_3$.xH$_2$O' for the second mark.

(b)

1. Painting/coating with plastic. This creates a barrier between the iron and the oxygen and water. Award one mark for stating painting or coating with plastic.

2. The barrier prevents oxygen and water from reaching the iron surface. This explains how the paint/plastic prevents corrosion. Award one mark for explaining that the barrier prevents oxygen and water from reaching the iron surface.

3. Galvanising. This involves coating the iron with a layer of zinc. Award one mark for stating galvanising.

4. Zinc is more reactive than iron and corrodes preferentially, acting as a sacrificial protection. / Zinc forms a protective oxide layer. This explains how galvanising prevents corrosion. Award one mark for explaining that zinc corrodes preferentially, acting as sacrificial protection or that zinc forms a protective oxide layer.

How to earn full marks:

• State a method such as 'painting' or 'galvanising' for one mark.
• Explain how the method prevents rusting (e.g., by creating a barrier or by sacrificial protection) for the second mark.
• Repeat this for the second method.

(c)

1. Order: 1 > 4 > 2 > 3 This is the correct order of rusting, from most to least. Award one mark for stating the correct order.

2. Test tube 1: Rusting occurs due to the presence of both water and oxygen. This explains why test tube 1 will have the most rust. Award one mark for explaining why test tube 1 will have the most rust.

3. Test tube 2: Boiling removes dissolved oxygen, and the oil layer prevents oxygen from dissolving in the water, slowing down rusting. This explains why test tube 2 will have less rust than test tube 1. Award one mark for explaining why test tube 2 will have less rust.

4. Test tube 3: Anhydrous calcium chloride absorbs moisture, preventing rusting. This explains why test tube 3 will have the least rust. Award one mark for explaining why test tube 3 will have the least rust.

How to earn full marks:

• State the correct order of rusting (1 > 4 > 2 > 3).
• Explain why test tube 1 will have the most rust.
• Explain why test tube 2 will have less rust.
• Explain why test tube 3 will have the least rust.

Common Pitfall: Remember that rust requires both water and oxygen. When explaining how methods prevent rusting, be sure to mention which of these is being excluded. In part (c), pay close attention to the conditions in each test tube and how they affect the availability of water and oxygen.

Exam-Style Question 4 — Extended Response [8 marks]

Question:

Alloys are mixtures of two or more metals, or a metal and a non-metal. Alloys often have different properties than the pure metals they are made from.

(a) Define the term alloy. [1]

(b) State two reasons why alloys are often preferred over pure metals. [2]

(c) Describe the structure of a pure metal and the structure of an alloy. Explain how the different structures affect their properties, such as malleability and hardness. [5]

Worked Solution:

(a)

1. A mixture of two or more metals, or a metal and a non-metal. This is the correct definition of an alloy. Award one mark for stating the correct definition of an alloy.

How to earn full marks:

• State the correct definition of an alloy as a mixture of two or more metals, or a metal and a non-metal.

(b)

1. Alloys are often harder than pure metals. This makes them more durable and resistant to deformation. Award one mark for stating alloys are often harder than pure metals.

2. Alloys are often more resistant to corrosion than pure metals. This makes them suitable for use in harsh environments. Award one mark for stating alloys are often more resistant to corrosion than pure metals.

How to earn full marks:

• State two valid reasons why alloys are preferred over pure metals (e.g., hardness, corrosion resistance).

(c)

1. Pure metals have a regular arrangement of atoms in layers. This describes the structure of a pure metal. Award one mark for describing the regular arrangement of atoms in a pure metal.

2. Alloys have a distorted arrangement of atoms because different sized atoms are mixed in. This describes the structure of an alloy, where the regular arrangement is disrupted. Award one mark for describing the distorted arrangement of atoms in an alloy.

3. In a pure metal, the layers of atoms can easily slide over each other, making them malleable. This explains why pure metals are malleable. Award one mark for explaining the malleability of pure metals.

4. In an alloy, the different sized atoms disrupt the layers, making it harder for them to slide over each other, making them harder and less malleable. This explains why alloys are harder and less malleable than pure metals. Award one mark for explaining the increased hardness and reduced malleability of alloys.

5. The distorted structure of the alloy makes it harder for the layers of atoms to slide. Therefore, alloys are harder than pure metals. Relating structure to hardness. Award one mark for relating the distorted structure of the alloy to its increased hardness.

How to earn full marks:

• Describe the regular arrangement of atoms in pure metals.
• Describe the distorted arrangement of atoms in alloys.
• Explain how the regular arrangement contributes to malleability in pure metals.
• Explain how the distorted arrangement increases hardness and decreases malleability in alloys.
• Relate the distorted structure of the alloy to its increased hardness.

Common Pitfall: When describing the structure of alloys, remember that the key difference from pure metals is the irregularity caused by the different sized atoms. This disruption is what affects the properties. Don't just say "they are mixed together"; explain how this mixing changes the arrangement.