Cambridge IGCSE Chemistry  ·  0620 / 0971

Chemistry you can measure, not just memorise.

Every idea in the syllabus becomes something you can change and watch. See what the particles do, then learn exactly how to write it for full marks.

Open the collision lab Browse all 12 topics
Syllabus topics
12
Factors in the first lab
4
Scales in one zoom
109
Fig. 1 Energy of particles in a gas Sweeping
T
298 K
E ≥ Eₐ
5.6 %
rate
×1.00
pathway
uncatalysed
rate ∝collisions per second with E ≥ Eₐ
comparedwith 25 °C, no catalyst

Powers of ten

01What you see · 10 cm

Magnesium meets acid.

Drop magnesium ribbon into hydrochloric acid and it fizzes. Keep scrolling to zoom in — one power of ten at a time — and find out why.

Watch for
bubbles of hydrogen
Equation
Mg + 2HCl → MgCl₂ + H₂

02Under a microscope · 10 µm

Still looks calm.

Even ten thousand times bigger the liquid looks still. Everything that decides the rate happens far below this scale.

Magnification
× 10 000
Seen
water and acid particles

03Particles · 1 nm

Particles, everywhere.

Acid particles race around and strike the metal surface millions of times every second. Only some of those hits make product.

Acid particle
moves freely
Metal surface
fixed lattice

04One collision · 0.1 nm

Most collisions just bounce.

These two particles meet, but the energy of the collision is below the activation energy. Nothing breaks, nothing forms — they fly apart.

Energy
below Eₐ
Result
no reaction

05One collision · 0.1 nm

Enough energy? Reaction.

When the collision energy reaches the activation energy, bonds break and new ones form. Rate is simply how often that happens.

Energy
≥ Eₐ
Result
a new product
Run it yourself in the lab
Fig. 2 Magnesium in hydrochloric acidfield of view 10 cm
collision energy Eₐ —

§1  The syllabus

Twelve topics, one syllabus.

Lessons go live one topic at a time. Each one is a lab you can change, a short explanation in the language examiners reward, and a quick check.

  • Live
  • Coming soon
06Live now

Chemical reactions

Rates of reaction, reversible reactions and redox. Start with why reactions go faster at all.

Lessons

  1. 6.1Collision theoryStart · 15 min
  2. 6.2Measuring the rate of a reactionsoon
  3. 6.3Surface area and particle sizesoon
  4. 6.4Reversible reactions and equilibriumsoon
  5. 6.5Redoxsoon
0 / 5 lessons
Open 6.1 Collision theory
020406080100 04080 volume of H₂ / cm³ t / s 50 °C 25 °C steeper = faster same final volume

§2  How a lesson works

See it, explain it, write it.

Every lesson follows the same three steps, built around how examiners award marks: intuition first, then the exact wording that scores.

  1. i.

    See it

    Change one factor and watch the particles. Every number on screen comes from the simulation, not from a picture.

    Example

    Heat the mixture from 25 °C to 150 °C. Watch what happens to the share of collisions that succeed.

    FallsSameRises
  2. ii.

    Explain it

    Each change comes with a short cause-and-effect chain, from the particles to the rate.

    Your readings
    T / °CE ≥ Eₐ
    2514 %
    10024 %
    15030 %
  3. iii.

    Write it

    Turn the chain into a full-mark answer, then check yourself with exam-style questions.

    Mark scheme · 3 marks

    “Particles have more kinetic energy, so a greater proportion of collisions have energy ≥ the activation energy.”

§3  Syllabus map

How the topics connect.

Topics build on each other: you need the mole before electrolysis, and bonding before organic chemistry. Each lesson you open fills in its topic here — progress is kept on this device only.

Fig. 3 Cambridge IGCSE Chemistry, 12 topics0 / 12 explored

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Open the collision lab