Catalysts

4CH1-3.124CH1-3.13

2 guided lessons · 18 checks · 3. Physical Chemistry → Rates of Reaction

Guided lessons for this note

Which concept don't you understand yet?

We'll explain it simply and check your understanding. Pick any lesson — any order works.

0 of 18 checks correct so far

Lesson 1 of 2

What a catalyst is and is not

A catalyst is chemistry's helper that is not used up: it speeds the reaction and walks away unchanged. This lesson pins down the definition, the small amounts needed and the way catalysts appear above reaction arrows.

What you know already

From Explaining Rates you already know why hotter, denser crowds of particles react faster. This note introduces the helper that speeds reactions without being consumed, the catalyst, and the alternative pathway that explains its power. Industrial chemistry leans on these substances every day.

Key points of understanding

A catalyst raises the rate of a reaction yet finishes it chemically unchanged.
Catalysts speed up reactions without themselves being altered or consumed.
Only small amounts of a catalyst are normally needed to have an effect.
Weigh a catalyst before and after a reaction and its mass reads exactly the same.
Catalysts are written above or below the reaction arrow rather than in the equation.

Diagram showing how iron acts as a catalyst for the Haber process

Tell us your confidence level against the key points

Choose a confidence level to continue.

Prefer to read it all at once? Show the full lesson as a page

1.What a catalyst is and is not

4CH1-3.12

Key points

A catalyst raises the rate of a reaction yet finishes it chemically unchanged.
Catalysts speed up reactions without themselves being altered or consumed.
Only small amounts of a catalyst are normally needed to have an effect.
Weigh a catalyst before and after a reaction and its mass reads exactly the same.

Guided content from the SME authoring corpus — note rn_tvwj4VZ6yFscPJfD, pinned at 51a6ed34e715 · promoted SyllabAI/syllabai-resources e967e75f1339

Back to the revision note All revision notes

2.How catalysts work and where industry uses them

4CH1-3.13

The shortcut is the secret: a catalyst offers the reaction an alternative pathway with a lower energy hurdle. This lesson walks that mechanism and meets the industrial catalysts built on it.

Reaction Kinetics - Iron Catalyst (2), downloadable AS & A Level Chemistry revision notes — Catalysts work by attracting reactant molecules on to the surface and so providing an alternate reaction pathway of lower energy

Key points

A catalyst opens a lower-energy route that lets more collisions succeed.
Different processes need different catalysts, but all work on the same principle.
Catalysts attract reactant molecules onto their surface, providing a lower-energy route.
Catalysis raises production rates and reduces energy costs in commercial chemistry.
Enzymes act as catalysts in biological systems.

First pass

Instead of the steep hill the reaction normally climbs, a catalyst opens a gentler path, so more particles can make the journey. The same idea serves every industry, and living cells use it too through enzymes.

Analogy — It is like a mountain road tunnelling through the pass: the summit stays the same, but far more lorries can make the crossing.

Exam pointer — Use the phrase alternative pathway with lower activation energy when explaining how catalysts work.

Going deeper

A catalyst opens an easier route whose lower energy hurdle lets a greater proportion of collisions succeed, so the rate rises. Atoms on the catalyst surface attract reactant molecules, and the same principle spans industrial processes and the enzymes of living systems.

Analogy — A ferry turns a long drive around the bay into a short crossing; the destination is unchanged, but the journey is easier and far more traffic completes it.

Exam pointer — Link the lowered barrier to more successful collisions, then name surface action and enzymes as extensions.

Checks

0 of 9 attempted · 0 correct

1.How does a catalyst speed up a reaction?
2.What happens to the activation energy of the uncatalysed route when a catalyst is added?
3.Iron in the ammonia process and vanadium(V) oxide in the sulfur process are examples of what?
4.Why does a lower-energy pathway raise the reaction rate?
5.Which biological molecules act as catalysts?
6.Name the biological molecules that speed up reactions in living systems without being used up.
Written response · recall
Your answer
7.State how a solid catalyst provides its lower-energy route.
Written response · recall
Your answer
8.Explain why more collisions succeed on a catalysed route.
Written response · explain why
Your answer
9.An industrial process switches to a better catalyst. State the two commercial gains recorded in industry.
Written response · application
Your answer