Factors Affecting Rate

ChemistryAQAGCSEUnit: Rates of Reaction
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The basics

Controlling the Speed of Chemistry

📖 Controlling the Speed of Chemistry

Why do we refrigerate food? To slow down the chemical reactions that cause decay. Why do we use a catalyst in car exhausts? To speed up the breakdown of toxic gases. Every day, we control reaction rates without even thinking about it. Crushing a sugar cube makes it dissolve faster. Using hot water makes a stain easier to remove. These aren't random observations — they're predictable consequences of collision theory. Once you understand WHY each factor works, you can predict and control reaction speeds in any situation.
🍳 The Cooking Analogy

Rate factors work just like cooking tips! Higher temperature (hot oven) = faster cooking. More concentration (more spice) = stronger reaction. Surface area (chopped vs whole veg) = faster cooking. Catalyst (pressure cooker) = speeds things up without being used up. Once you understand these principles, chemistry becomes as intuitive as cooking!

Spotlight
The Four Factors That Affect Rate

For gases: increasing PRESSURE has the same effect.

Exam tip

Earn the mark scheme marks

🧠 Memory Aid: CCTSP

Remember the five factors that affect rate of reaction using CCTSP:

  • C — Concentration (more particles per volume)
  • C — Catalyst (lowers activation energy)
  • T — Temperature (faster particles, more exceed Ea)
  • S — Surface area (more exposed particles)
  • P — Pressure (for gases — same as concentration)

Picture a chef (C) cooking (C) in the Test kitchen (T) with Special (S) Pans (P) — CCTSP rules the kitchen of chemistry!

Now try it yourself

Quiz · Question 1 of 24

Which of the following factors does NOT affect the rate of a chemical reaction?

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