Physical properties of metals

Definition

Malleable

Able to be hammered or pressed into a new shape without breaking.

Definition

Ductile

Able to be drawn out into thin wires without breaking.

Elements can be sorted into metals and non-metals by comparing their physical properties, which are features you can observe or measure without making a new substance.
Thermal conductivity: metals are good thermal conductors, so heat passes through them quickly.
1. The handle of a metal spoon left standing in a cup of hot tea soon becomes hot.
2. Most non-metals are poor thermal conductors, so they act as thermal insulators.
Electrical conductivity: metals are good electrical conductors when they are solid and when they are molten.
1. Most non-metals do not conduct electricity, so they are electrical insulators.
2. Graphite, a form of carbon, is the main exception, because it is a non-metal that conducts electricity.
Malleability and ductility: metals are malleable and ductile, so they can be hammered into thin sheets and drawn out into wires.
1. Solid non-metals such as sulfur and phosphorus are brittle, so they shatter or crumble when hit instead of changing shape.
Melting points and boiling points: most metals have high melting points and boiling points, so nearly all of them are solids at room temperature.
1. Iron melts at about $∘C1538\ ^\circ\text{C}$ and copper melts at about $∘C1085\ ^\circ\text{C}$ .
2. Most non-metals have low melting points and boiling points, so many of them, such as oxygen, nitrogen and chlorine, are gases at room temperature.
These are general trends, so a few elements do not fit them.
1. Mercury is a metal that is a liquid at room temperature, and sodium is a metal that melts below $∘C100\ ^\circ\text{C}$ .
2. Diamond and graphite are forms of the non-metal carbon, yet both have very high melting points.
Metals share this set of properties because of the metallic bonding that holds their atoms together.

Practical

Testing the electrical conductivity of elements

Aim: to sort a set of solid elements into metals and non-metals by testing whether each one conducts electricity.
Apparatus: a $V1.5\ \text{V}$ cell in a holder, a small filament lamp in a holder, three connecting leads, two crocodile clips, emery paper, and samples of copper foil, zinc foil, magnesium ribbon, an iron nail, aluminium foil, a graphite rod and a lump of sulfur.
Method, setting up:
- Connect the cell, the lamp and the leads in a single loop, leaving a gap between the two crocodile clips.
- Touch the two crocodile clips together and check that the lamp lights, which shows that the circuit itself works.
- Rub each metal sample with emery paper until it is shiny, so that the dull surface coating is removed and clean metal is exposed.
Method, testing the samples:
- Attach the crocodile clips to opposite ends of the first sample so that the sample completes the circuit.
- Watch the lamp and record whether it lights brightly, lights dimly or stays off.
- Disconnect the sample and repeat the test with each of the other samples in turn.
- Record your observations in a table with the headings element, lamp lit or not lit, and metal or non-metal.
Results: the lamp lights for copper, zinc, magnesium, iron and aluminium, it also lights for the graphite rod, and it stays off for sulfur.
Conclusion: every metal conducts electricity, while sulfur is an insulator and graphite is an unusual non-metal that conducts.
Watch out: a dull surface coating on a metal can stop the lamp from lighting, so a metal that has not been cleaned may give a false result.
Safety: use only a low-voltage cell, and disconnect each sample after testing because the leads and samples can become warm.

Reactions with dilute acids

Definition

Effervescence

The rapid release of bubbles of gas from a liquid during a chemical reaction.

Many metals react with dilute acids to form a salt and hydrogen gas.
The general word equation is $metal+acid→salt+hydrogen\text{metal} + \text{acid} \rightarrow \text{salt} + \text{hydrogen}$ .
The salt is named from the metal and the acid, so hydrochloric acid forms chlorides and sulfuric acid forms sulfates.
Magnesium reacts with dilute hydrochloric acid to form magnesium chloride and hydrogen: $Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g)\mathrm{Mg(s) + 2HCl(aq) \rightarrow MgCl_2(aq) + H_2(g)}$ .
Zinc reacts with dilute sulfuric acid to form zinc sulfate and hydrogen: $Zn(s)+H2SO4(aq)→ZnSO4(aq)+H2(g)\mathrm{Zn(s) + H_2SO_4(aq) \rightarrow ZnSO_4(aq) + H_2(g)}$ .
During these reactions you see effervescence, the metal gets smaller and disappears if enough acid is present, and the test tube becomes warm.
The gas is shown to be hydrogen because it pops with a lighted splint.
Some metals, including copper, silver and gold, do not react with dilute acids at all.

Reactions with water and steam

Some metals react with cold water to form a metal hydroxide and hydrogen.
The general word equation is $hydroxide+hydrogen\text{metal} + \text{water} \rightarrow \text{metal hydroxide} + \text{hydrogen}$ .
Sodium reacts with cold water to form sodium hydroxide and hydrogen: $2Na(s)+2H2O(l)→2NaOH(aq)+H2(g)\mathrm{2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g)}$ .
The metal hydroxide dissolves to give an alkaline solution, so universal indicator added to the water turns blue or purple.
Metals that react very slowly or not at all with cold water may still react when they are heated in steam, which is water in the gas state.
With steam the products are a metal oxide and hydrogen, because the oxide forms instead of the hydroxide at these high temperatures.
The general word equation is $oxide+hydrogen\text{metal} + \text{steam} \rightarrow \text{metal oxide} + \text{hydrogen}$ .
Magnesium heated in steam forms magnesium oxide and hydrogen: $Mg(s)+H2O(g)→MgO(s)+H2(g)\mathrm{Mg(s) + H_2O(g) \rightarrow MgO(s) + H_2(g)}$ .
Copper, silver and gold do not react with water or with steam.

Reactions with oxygen

Definition

Oxidation (in terms of oxygen)

The gain of oxygen by a substance.

Most metals react with oxygen to form a metal oxide, and no hydrogen is produced.
The general word equation is $oxide\text{metal} + \text{oxygen} \rightarrow \text{metal oxide}$ .
Magnesium ribbon burns in air with a dazzling white flame and leaves a white powder of magnesium oxide: $2Mg(s)+O2(g)→2MgO(s)\mathrm{2Mg(s) + O_2(g) \rightarrow 2MgO(s)}$ .
Iron filings sprinkled into a hot flame burn with bright orange sparks.
Copper does not burn, but when it is heated strongly in air its surface turns black as copper(II) oxide forms: $2Cu(s)+O2(g)→2CuO(s)\mathrm{2Cu(s) + O_2(g) \rightarrow 2CuO(s)}$ .
Gold does not react with oxygen even when it is heated, which is why gold jewellery keeps its shine for centuries.
In each of these reactions the metal gains oxygen, so the metal is oxidised.

Example

One metal, three sets of products

The products of a metal's reaction depend on what it reacts with, as zinc shows.
Zinc added to dilute hydrochloric acid fizzes steadily and forms zinc chloride and hydrogen.

\mathrm{Zn(s) + 2HCl(aq) \rightarrow ZnCl_2(aq) + H_2(g)}

Zinc heated in steam forms zinc oxide and hydrogen, not zinc hydroxide.

\mathrm{Zn(s) + H_2O(g) \rightarrow ZnO(s) + H_2(g)}

Zinc heated in oxygen forms zinc oxide as the only product.

\mathrm{2Zn(s) + O_2(g) \rightarrow 2ZnO(s)}

Exam technique

Describing what you see

When a gas is given off, write effervescence, fizzing or bubbles, because a statement such as "hydrogen is made" names the product but does not describe an observation.
Give the test for hydrogen in full: a lighted splint placed at the mouth of the tube gives a squeaky pop.
When a metal reacts with an excess of acid, say that the metal dissolves or disappears, never that it "melts".
When you compare metals and non-metals, use the property words conductor, malleable, ductile and brittle rather than everyday words such as "bendy".

Common Mistake

Do not give a metal hydroxide as the product when a metal reacts with steam, because steam gives a metal oxide.
Do not include hydrogen as a product when a metal burns in oxygen.
Do not describe graphite as a metal just because it conducts electricity.

Self review

What does it mean when a metal is described as ductile?
Which non-metal element conducts electricity?
What are the products when a metal reacts with a dilute acid?
How do the products differ when a metal reacts with cold water and when it reacts with steam?
What do you see when magnesium ribbon burns in air?

Physical properties of metals

Definition

Malleable

Able to be hammered or pressed into a new shape without breaking.

Definition

Ductile

Able to be drawn out into thin wires without breaking.

Elements can be sorted into metals and non-metals by comparing their physical properties, which are features you can observe or measure without making a new substance.
Thermal conductivity: metals are good thermal conductors, so heat passes through them quickly.
1. The handle of a metal spoon left standing in a cup of hot tea soon becomes hot.
2. Most non-metals are poor thermal conductors, so they act as thermal insulators.
Electrical conductivity: metals are good electrical conductors when they are solid and when they are molten.
1. Most non-metals do not conduct electricity, so they are electrical insulators.
2. Graphite, a form of carbon, is the main exception, because it is a non-metal that conducts electricity.
Malleability and ductility: metals are malleable and ductile, so they can be hammered into thin sheets and drawn out into wires.
1. Solid non-metals such as sulfur and phosphorus are brittle, so they shatter or crumble when hit instead of changing shape.
Melting points and boiling points: most metals have high melting points and boiling points, so nearly all of them are solids at room temperature.
1. Iron melts at about $∘C1538\ ^\circ\text{C}$ and copper melts at about $∘C1085\ ^\circ\text{C}$ .
2. Most non-metals have low melting points and boiling points, so many of them, such as oxygen, nitrogen and chlorine, are gases at room temperature.
These are general trends, so a few elements do not fit them.
1. Mercury is a metal that is a liquid at room temperature, and sodium is a metal that melts below $∘C100\ ^\circ\text{C}$ .
2. Diamond and graphite are forms of the non-metal carbon, yet both have very high melting points.
Metals share this set of properties because of the metallic bonding that holds their atoms together.

Practical

Testing the electrical conductivity of elements

Aim: to sort a set of solid elements into metals and non-metals by testing whether each one conducts electricity.
Apparatus: a $V1.5\ \text{V}$ cell in a holder, a small filament lamp in a holder, three connecting leads, two crocodile clips, emery paper, and samples of copper foil, zinc foil, magnesium ribbon, an iron nail, aluminium foil, a graphite rod and a lump of sulfur.
Method, setting up:
- Connect the cell, the lamp and the leads in a single loop, leaving a gap between the two crocodile clips.
- Touch the two crocodile clips together and check that the lamp lights, which shows that the circuit itself works.
- Rub each metal sample with emery paper until it is shiny, so that the dull surface coating is removed and clean metal is exposed.
Method, testing the samples:
- Attach the crocodile clips to opposite ends of the first sample so that the sample completes the circuit.
- Watch the lamp and record whether it lights brightly, lights dimly or stays off.
- Disconnect the sample and repeat the test with each of the other samples in turn.
- Record your observations in a table with the headings element, lamp lit or not lit, and metal or non-metal.
Results: the lamp lights for copper, zinc, magnesium, iron and aluminium, it also lights for the graphite rod, and it stays off for sulfur.
Conclusion: every metal conducts electricity, while sulfur is an insulator and graphite is an unusual non-metal that conducts.
Watch out: a dull surface coating on a metal can stop the lamp from lighting, so a metal that has not been cleaned may give a false result.
Safety: use only a low-voltage cell, and disconnect each sample after testing because the leads and samples can become warm.

Reactions with dilute acids

Definition

Effervescence

The rapid release of bubbles of gas from a liquid during a chemical reaction.

Many metals react with dilute acids to form a salt and hydrogen gas.
The general word equation is $metal+acid→salt+hydrogen\text{metal} + \text{acid} \rightarrow \text{salt} + \text{hydrogen}$ .
The salt is named from the metal and the acid, so hydrochloric acid forms chlorides and sulfuric acid forms sulfates.
Magnesium reacts with dilute hydrochloric acid to form magnesium chloride and hydrogen: $Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g)\mathrm{Mg(s) + 2HCl(aq) \rightarrow MgCl_2(aq) + H_2(g)}$ .
Zinc reacts with dilute sulfuric acid to form zinc sulfate and hydrogen: $Zn(s)+H2SO4(aq)→ZnSO4(aq)+H2(g)\mathrm{Zn(s) + H_2SO_4(aq) \rightarrow ZnSO_4(aq) + H_2(g)}$ .
During these reactions you see effervescence, the metal gets smaller and disappears if enough acid is present, and the test tube becomes warm.
The gas is shown to be hydrogen because it pops with a lighted splint.
Some metals, including copper, silver and gold, do not react with dilute acids at all.

Reactions with water and steam

Some metals react with cold water to form a metal hydroxide and hydrogen.
The general word equation is $hydroxide+hydrogen\text{metal} + \text{water} \rightarrow \text{metal hydroxide} + \text{hydrogen}$ .
Sodium reacts with cold water to form sodium hydroxide and hydrogen: $2Na(s)+2H2O(l)→2NaOH(aq)+H2(g)\mathrm{2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g)}$ .
The metal hydroxide dissolves to give an alkaline solution, so universal indicator added to the water turns blue or purple.
Metals that react very slowly or not at all with cold water may still react when they are heated in steam, which is water in the gas state.
With steam the products are a metal oxide and hydrogen, because the oxide forms instead of the hydroxide at these high temperatures.
The general word equation is $oxide+hydrogen\text{metal} + \text{steam} \rightarrow \text{metal oxide} + \text{hydrogen}$ .
Magnesium heated in steam forms magnesium oxide and hydrogen: $Mg(s)+H2O(g)→MgO(s)+H2(g)\mathrm{Mg(s) + H_2O(g) \rightarrow MgO(s) + H_2(g)}$ .
Copper, silver and gold do not react with water or with steam.

Reactions with oxygen

Definition

Oxidation (in terms of oxygen)

The gain of oxygen by a substance.

Most metals react with oxygen to form a metal oxide, and no hydrogen is produced.
The general word equation is $oxide\text{metal} + \text{oxygen} \rightarrow \text{metal oxide}$ .
Magnesium ribbon burns in air with a dazzling white flame and leaves a white powder of magnesium oxide: $2Mg(s)+O2(g)→2MgO(s)\mathrm{2Mg(s) + O_2(g) \rightarrow 2MgO(s)}$ .
Iron filings sprinkled into a hot flame burn with bright orange sparks.
Copper does not burn, but when it is heated strongly in air its surface turns black as copper(II) oxide forms: $2Cu(s)+O2(g)→2CuO(s)\mathrm{2Cu(s) + O_2(g) \rightarrow 2CuO(s)}$ .
Gold does not react with oxygen even when it is heated, which is why gold jewellery keeps its shine for centuries.
In each of these reactions the metal gains oxygen, so the metal is oxidised.

Example

One metal, three sets of products

The products of a metal's reaction depend on what it reacts with, as zinc shows.
Zinc added to dilute hydrochloric acid fizzes steadily and forms zinc chloride and hydrogen.

\mathrm{Zn(s) + 2HCl(aq) \rightarrow ZnCl_2(aq) + H_2(g)}

Zinc heated in steam forms zinc oxide and hydrogen, not zinc hydroxide.

\mathrm{Zn(s) + H_2O(g) \rightarrow ZnO(s) + H_2(g)}

Zinc heated in oxygen forms zinc oxide as the only product.

\mathrm{2Zn(s) + O_2(g) \rightarrow 2ZnO(s)}

Exam technique

Describing what you see

When a gas is given off, write effervescence, fizzing or bubbles, because a statement such as "hydrogen is made" names the product but does not describe an observation.
Give the test for hydrogen in full: a lighted splint placed at the mouth of the tube gives a squeaky pop.
When a metal reacts with an excess of acid, say that the metal dissolves or disappears, never that it "melts".
When you compare metals and non-metals, use the property words conductor, malleable, ductile and brittle rather than everyday words such as "bendy".

Common Mistake

Do not give a metal hydroxide as the product when a metal reacts with steam, because steam gives a metal oxide.
Do not include hydrogen as a product when a metal burns in oxygen.
Do not describe graphite as a metal just because it conducts electricity.

Self review

What does it mean when a metal is described as ductile?
Which non-metal element conducts electricity?
What are the products when a metal reacts with a dilute acid?
How do the products differ when a metal reacts with cold water and when it reacts with steam?
What do you see when magnesium ribbon burns in air?

9.1.1 Physical and chemical properties of metals

Physical properties of metals

Testing the electrical conductivity of elements

Reactions with dilute acids

Reactions with water and steam

Reactions with oxygen

One metal, three sets of products

Describing what you see

Review 9.1.1 Physical and chemical properties of metals by teaching Genie

9.1.1 Physical and chemical properties of metals

Physical properties of metals

Testing the electrical conductivity of elements

Reactions with dilute acids

Reactions with water and steam

Reactions with oxygen

One metal, three sets of products

Describing what you see

Review 9.1.1 Physical and chemical properties of metals by teaching Genie

9.1.1 Physical and chemical properties of metals

Physical properties of metals

Testing the electrical conductivity of elements

Reactions with dilute acids

Reactions with water and steam

Reactions with oxygen

One metal, three sets of products

Describing what you see

Review 9.1.1 Physical and chemical properties of metals by teaching Genie

9.1.1 Physical and chemical properties of metals Revision Guide

9.1.1 Physical and chemical properties of metals

Physical properties of metals

Testing the electrical conductivity of elements

Reactions with dilute acids

Reactions with water and steam

Reactions with oxygen

One metal, three sets of products

Describing what you see

Review 9.1.1 Physical and chemical properties of metals by teaching Genie

9.1.1 Physical and chemical properties of metals Revision Guide