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Reaction Kinetics: an interactive rates of reaction course

Published 8 Nov 20265 min read

Reaction Kinetics is an interactive reaction kinetics course about how fast chemical reactions go and why. Its 25 short sections cover measuring rates from tables and graphs, collision theory, energy profiles and activation energy, temperature and the Maxwell-Boltzmann distribution, concentration, pressure and surface area, catalysts, rate equations and orders, and reversible reactions reaching equilibrium.

It opens with a box of reactant particles where only collisions with enough energy react, and a temperature slider that shows the rate climbing as you heat it.

What the course covers

Sections	Topic	What you do
1 to 5	What reaction rate is, and measuring it from tables and graphs	Calculate a mean rate, then compare two runs on one graph
6 to 7	Collision theory	Sort collisions into ones that react and ones that do not
8 to 10	Energy profile diagrams	Label a profile, then read the activation energy and energy change
11 to 13	Temperature and the Maxwell-Boltzmann distribution	Pick the curve for a hotter gas, a cooler gas or a catalyst
14 to 17	Concentration, pressure and surface area	Match each change to its reason, then rank experiments by speed
18 to 19	Catalysts	Say what each change does to collisions and activation energy
20 to 23	Rate equations and orders	Find the orders from data, then use rate = k[A]
24 to 25	Reversible reactions and equilibrium	Spot when equilibrium is reached on a graph

Measuring rate

Rate is how fast products form or reactants are used up. Collect gas or record mass lost over time, then divide the change by the time taken. On a graph of product against time, the line climbs fastest early on, then levels off as the reactants get used up.

\text{mean rate}=\frac{\text{change in amount}}{\text{time taken}}

y = 80\cdot\left(1-{ e}^{\left(\frac{- x}{20}\right)}\right)

Open in graph

Drag to pan, scroll to zoom. x from 0 to 100, y from -15.9 to 95.4.

Here x is time in seconds and y is the volume of gas in cm³, for an example reaction. The mean rate over the first 20 s is 50.6 ÷ 20 = 2.5 cm³/s, and the curve flattens towards 80 cm³ as the reactant is used up.

Why rates change

A collision only leads to a reaction if it carries enough energy, the activation energy. Higher temperature makes particles faster and more energetic, so far more collisions succeed, as the Maxwell-Boltzmann distribution shows. Higher concentration, pressure or surface area make collisions more frequent. A catalyst opens an easier pathway that needs less energy, and it is still there at the end.

Rate equations and equilibrium

For advanced students, rate equations such as rate = k[A]² link rate to concentration, with orders found from experiments rather than the balanced equation. The course ends with reversible reactions, where forward and backward rates become equal at equilibrium.

Try a question from the course

A reaction gives off 60 cm³ of gas in its first 30 seconds. The mean rate over that time is 60 ÷ 30 = 2 cm³/s. To find the mean rate between two later times, use the change in volume between them divided by the time between them.

Now work out a mean rate from a new table, then press Mark to check your answer in the course.

Press Mark to have your answer marked in the Reaction Kinetics course.

Who this course is for

GCSE chemistry students revising rates of reaction, collision theory, catalysts and reversible reactions.
A-level and other advanced students working on the Maxwell-Boltzmann distribution, rate equations and orders.
Anyone who wants to know why food lasts longer in a fridge and why powders burn faster than lumps.

What you need to know first

The course page suggests Chemical Bonding first, for particles, bonds and energy changes. You need to read graphs and divide, and the rate equation sections use simple powers.

How long it takes

There are 25 sections and most take a few minutes. Learners without a plan can open two sections of a course a day, in order, so the whole course takes 13 days. A plan removes the daily limit and lets you go straight to any topic, such as rate equations.

Guided courseOrganic ChemistryAlkanes, alkenes, functional groups and polymers, from carbon's four bonds up.

Common questions

Is this reaction kinetics course free?

You can take every section without paying, two sections a day, in order. A plan removes the daily limit and opens any section straight away.

What factors affect the rate of a reaction?

Temperature, concentration of solutions, pressure of gases, surface area of solids, and the use of a catalyst. Each one changes how often particles collide or how many collisions have enough energy.

What is collision theory?

Reactions happen only when particles hit each other hard enough: the energy of the collision has to reach a threshold called the activation energy. Anything that makes successful collisions more frequent speeds the reaction up.

How does a catalyst work?

It gives the reaction a different pathway that needs less energy to get over, so a bigger share of collisions succeed. It is not used up, so a small amount works for a long time.

What is activation energy?

The smallest amount of energy a collision must have for a reaction to start. On an energy profile it is the height of the hump above the reactants.

What is a rate equation?

An equation such as rate = k[A][B]² that shows how the rate depends on the concentration of each reactant. The powers are the orders, found by experiment.

Revision cards

Say the answer first, then flip the card to check it.

Where to go next

Solve it
Rate of Change Calculator
Find average and instantaneous rates of change
Open the tool
Learn it
Reaction Kinetics
Rates, catalysts and collision theory: what makes reactions fast or slow
Start the course
Test it
GCSE Chemistry Higher
A new exam-style paper every day, with instant marking and a mark scheme
Start today's paper