Reactivity series Revision Notes for AQA GCSE Chemistry Combined Science

Reactivity series

What is the reactivity series?

The reactivity series is a list that shows metals in order of how reactive they are. When metals react, they lose electrons to form positive ions. The easier it is for a metal to form positive ions, the more reactive it is.

The most reactive metals are at the top of the list, and the least reactive metals are at the bottom.

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The reactivity series is also known as the "activity series" and is fundamental to understanding how different metals behave in chemical reactions. This ordering helps predict which reactions will occur and how vigorous they will be.

The order of metals in the reactivity series

From most reactive to least reactive:

Potassium - reacts very vigorously with water and acid
Sodium - reacts vigorously with water and acid
Lithium - reacts steadily with water, vigorously with acid
Calcium - fizzes with water, reacts vigorously with acid
Magnesium - reacts very slowly with water, fizzes with acid
Carbon - doesn't react with water or acid (non-metal)
Zinc - no reaction with water, fizzes with acid
Iron - no reaction with water, reacts very slowly with acid
Hydrogen - used as a reference point
Copper - no reaction with water or acid

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Carbon and hydrogen are often included in the reactivity series even though they're not metals. This helps us understand displacement reactions and provides useful reference points for predicting chemical behaviour.

How metals react with water and acids

Understanding how metals interact with water and acids is essential for predicting reaction outcomes. The position of a metal in the reactivity series directly determines how it will behave in these reactions.

Reactions with water

When reactive metals react with water, they produce a metal hydroxide and hydrogen gas.

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Chemical Equation Example: Lithium and Water

$\text{Lithium} + \text{Water} \rightarrow \text{Lithium hydroxide} + \text{Hydrogen}$

$2\text{Li} + 2\text{H}_2\text{O} \rightarrow 2\text{LiOH} + \text{H}_2$

The more reactive the metal, the more vigorous the reaction. You'll see more fizzing and bubbling with metals higher up in the series.

Reactions with dilute acids

When metals react with dilute acids, they produce a metal salt and hydrogen gas.

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Chemical Equation Example: Magnesium and Hydrochloric Acid

$\text{Magnesium} + \text{Hydrochloric acid} \rightarrow \text{Magnesium chloride} + \text{Hydrogen}$

$\text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2$

Again, more reactive metals will fizz and react faster than less reactive ones.

Displacement reactions

A displacement reaction happens when a more reactive metal takes the place of a less reactive metal in a compound. These reactions are fundamental to understanding metal chemistry and have many practical applications.

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Key Rules for Displacement Reactions:

A more reactive metal will displace a less reactive metal from its compound
A less reactive metal cannot displace a more reactive metal
The reaction only occurs if there's a significant difference in reactivity

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Worked Example: Displacement Reactions

Reaction 1: Zinc + Copper sulphate $\text{Zn} + \text{CuSO}_4 \rightarrow \text{ZnSO}_4 + \text{Cu}$ This reaction occurs because zinc is more reactive than copper.

Reaction 2: Magnesium + Zinc oxide $\text{Mg} + \text{ZnO} \rightarrow \text{MgO} + \text{Zn}$ This reaction occurs because magnesium is more reactive than zinc.

Reaction 3: Carbon + Zinc oxide (industrial process) $\text{C} + \text{ZnO} \rightarrow \text{Zn} + \text{CO}$ This reaction occurs because carbon can displace zinc from its oxide.

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Why do displacement reactions happen? The more reactive metal forms positive ions more easily, so it "steals" the negative ions from the less reactive metal's compound. This is because the more reactive metal has a stronger tendency to lose electrons.

Using the reactivity series

You can use the reactivity series to predict several important aspects of chemical reactions:

Whether a reaction will happen - compare positions in the series
How vigorous a reaction will be - greater difference means more vigorous reaction
What products will form in displacement reactions

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Quick Tip for Predictions: Look at the position of metals in the series. If one metal is higher up than another, it's more reactive and can displace it. The further apart they are in the series, the more vigorous the reaction will be.

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Key Points to Remember:

The reactivity series lists metals from most reactive (top) to least reactive (bottom)
More reactive metals form positive ions more easily
Reactive metals fizz and bubble when they react with water or acids
More reactive metals can displace less reactive metals from their compounds
Carbon is often included in the series to help predict reactions with metal oxides
The greater the difference in reactivity, the more vigorous the reaction will be

Reactivity series (AQA GCSE Chemistry Combined Science): Revision Notes