GCSE · Chemistry · AQA · Spec 8462

Catalysts

A catalyst changes how quickly a reaction happens without disappearing into the products — the key is the lower-energy route it provides.

Why does a catalyst speed the reaction?

?

Reason it through

Trace catalytic action from pathway to rate.

Link 1 of 3

First link · your turn

What does the catalyst provide?

2
Locked — reveal the link above first
3
Locked — reveal the link above first

Spot the catalyst

Use both clues: rate and what happens to the substance.

Substance X is added to a reaction. The reaction becomes faster, X is recovered afterwards, and X is not included in the chemical equation. What is the best conclusion?

Relationship matrix

Tap any cell to reveal it. Tap a column header to read one property down every item.

Effect on rateUsed up?How it works
Chemical catalystreaction-specific
Enzymebiological catalyst

Each cell hides a short answer and the reason behind it. Predict before you tap.

The catalyst mechanism in one chain

1pathway2345

Stage 1 of 5: pathway. paused

pathway · 1/5Scrub from pathway to rate.

A different route becomes available.

Step through what changes — and what does not.

CHEMISTRY

A catalyst speeds a reaction by opening a lower-energy pathway — and survives to do it again.

What you need to know

  • A catalyst changes reaction rate but is not used up.
  • Catalysts provide a different pathway with a lower activation energy.
  • A catalyst can be identified from its effect on rate and because it is not included in the reaction equation.
  • Different reactions need different catalysts, and enzymes are biological catalysts.

The big picture

A catalyst increases reaction rate without being used up. It works by providing a different reaction pathway with a lower activation energy.

Key points

1A catalyst changes the rate of a chemical reaction but is not used up.
2Catalysts increase reaction rate by providing a different pathway with a lower activation energy.
3Different reactions need different catalysts.
4Enzymes are catalysts in biological systems.
5A catalyst can be identified because it increases rate, is not used up, and is not included in the chemical equation for the reaction.

Worked example

Problem

A student adds substance X to a reaction. The reaction finishes sooner. At the end, X can still be recovered, and X does not appear in the reaction equation. Explain what X is and why.

🧠

Memory hook

Catalyst = easier route, lower barrier, faster reaction — still there at the end.

★ Exam tip

If asked to explain a catalyst, do not stop at 'it speeds the reaction'. Add: different pathway with a lower activation energy.

⚠ Watch out

Do not say a catalyst gives particles extra energy or is used up. It lowers the activation-energy barrier by providing a different pathway.

✓

Check yourself

Without looking: give the three-part chain that explains how a catalyst increases reaction rate.

Flashcards

(20)
What is a catalyst?
A substance that changes the rate of a chemical reaction but is not used up during the reaction.
Do catalysts get used up during the reaction?
No.
What effect does a catalyst have on reaction rate?
It increases the rate.
How does a catalyst increase reaction rate?
It provides a different reaction pathway with a lower activation energy.
What happens to activation energy when a catalyst is used?
The reaction has a pathway with lower activation energy.
Does a catalyst give reacting particles extra energy?
No. It provides a lower-activation-energy pathway.
What is an enzyme?
A catalyst in a biological system.
Do all reactions use the same catalyst?
No. Different reactions need different catalysts.
Give one clue that a substance is a catalyst.
It increases the reaction rate.
Give a second clue that a substance is a catalyst.
It is not used up during the reaction.
Give a third clue used to identify a catalyst in the packet.
It is not included in the chemical equation for the reaction.
Complete the chain: different pathway → ?
Lower activation energy → faster reaction.
Why does lower activation energy increase rate?
A greater proportion of collisions can lead to reaction under the same conditions.
What is activation energy?
The minimum energy barrier that reacting particles must overcome for reaction to occur.
Is a catalyst necessarily a reactant?
No. It is not used up and is not included as a reactant in the reaction equation.
Can a catalyst be recovered after a reaction?
Yes, because it is not used up.
What must an explanation of catalytic action mention?
A different pathway with lower activation energy.
What must you avoid saying about a catalyst?
That it is used up or that it supplies extra energy to particles.
How are enzymes and chemical catalysts similar?
Both act as catalysts and increase reaction rate without being used up.
What is the shortest useful catalyst memory chain?
Easier route → lower activation energy → faster reaction.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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