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Chemistry · Rates and Equilibrium

Reaction Rate / Collision Theory

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Wrap-up

What you learned

Recommended next: Open concept testCheck whether the core ideas are ready without leaving this concept.
Read next: Dynamic Equilibrium / Le Chatelier's PrincipleCarry the collision story into a reversible system that re-balances

Key takeaway

More collision attempts matter only when enough of them clear the threshold.
Heating changes the energy story as well as particle motion.
A catalyst raises the successful fraction by lowering the effective barrier.

Common misconception

Do not treat every collision as a reaction; read attempts and success fraction separately.

A crowded box mainly creates more collision attempts.

From collision theory to rate changes

Keep this idea moving

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Carry the collision story into a reversible system that re-balancesRates and Equilibrium

Dynamic Equilibrium / Le Chatelier's Principle

Watch a reversible chemistry bench keep changing microscopically while the mixture settles toward a new balance after each disturbance.

Useful comparisonThermodynamics

Temperature and Internal Energy

Compare average particle motion with whole-sample energy, vary amount and heating, and see why a phase-change shelf breaks naive temperature-only reasoning on one compact thermal bench.

Useful comparisonThermodynamics

Ideal Gas Law and Kinetic Theory

Connect pressure, volume, temperature, and particle number on one bounded particle box, then read the same pressure changes back as changes in particle speed and wall-collision rate.

Stay with this concept

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More practice optionsReview on the bench · Worked examples

Practice optionReview on the benchReplay the guided setup with the key controls and graphs in sight.
Practice optionWorked examplesCompare against solved walkthroughs after you try the setup yourself.
Practice optionFree play on the benchExperiment freely with the live controls before moving to another concept.

Reference and support

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Equation snapshotAttempts × success · Clearing the barrierShow 3 equations

Keep the attempt rate, threshold story, and catalyst shortcut visible together.

Attempts × success
$reaction rate \approx collision attempts \times successful fraction$
Separate how often particles meet from how often those meetings actually become reactions.
Clearing the barrier
$successful fraction ↑ when particle energy is large relative to the barrier$
Temperature helps by increasing the fraction of collisions with enough energy to get over the barrier.
Catalyst lowers the effective barrier
$E_{eff} = E_{a} - catalyst effect$
A catalyst changes the barrier side of the story without needing hotter particles.

Why it behaves this way

Explanation

Start with two separate questions: how often do particles collide, and how many of those collisions actually react? This bench keeps the particle box, threshold cue, and live rate readout together so you can see both parts of the rate story at once.

Concentration mostly changes how often particles get chances to collide. Temperature changes both collision frequency and the fraction energetic enough to clear the barrier. A catalyst changes the story in a different way: it lowers the effective barrier, so more collisions succeed without needing hotter particles.

Key ideas

01Reaction rate depends on successful collisions, not just on total collision attempts.

02Higher concentration mainly increases collision chances, while higher temperature also increases the fraction that can clear the barrier.

03A catalyst speeds the reaction by lowering the effective barrier, not by heating the particles or crowding the box.

Worked examples

Open examples when you want to see the same idea walked through step by step.

Frozen walkthrough

Step through the frozen example

Frozen walkthrough

Use the same particle box, threshold cue, and graphs. The goal is to read rate as collision frequency multiplied by success, not as a single mysterious number.

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Example 1 of 2

Frozen valuesUsing frozen parameters

For the current setup, what part of the rate comes from collision frequency and what part comes from barrier-clearing success?

T

Temperature

3.1

c

Concentration

1.4

E_{a}

Activation energy barrier

2.8

1. Read the collision attempt rate

At the current temperature and concentration, the box makes about 32.73 collision attempts each second.

2. Read the successful fraction

Only about 37.46% of those collisions clear the effective barrier.

3. Turn those into the reaction rate

That leaves about 12.26 successful collisions each second and about 20.47 unsuccessful ones.

Current reaction rate

rate \approx 12.26 successful collisions/s

The box is busy, but most hits still fail the barrier test, so all-collision count and successful-collision rate need to be kept separate.

Quick test

Loading saved test state.

Accessibility

Open the text-first descriptions when you need the simulation and graph translated into words.

The simulation shows a particle box with reactants moving and colliding, plus cues for total collisions, successful collisions, and the barrier that collisions must clear. Sliders change temperature, concentration, and activation threshold, and a toggle applies a catalyst.

A readout reports the current temperature, concentration, threshold, successful fraction, and successful-collision rate so the learner can connect the moving box to the graphs.

Graph summary

One graph compares all collision attempts with successful collisions as temperature changes, a second makes the same comparison as concentration changes, and a third shows the successful fraction against temperature.

Reading the box and the graphs together helps the learner separate two ideas: how often particles collide and how often those collisions actually react.

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Baseline mixture preset

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Featured setups

Crowded but cool

Open a crowded, low-temperature box and compare frequent collision attempts with the much smaller number of successful collisions.

Catalyzed threshold

Open a lower-barrier setup and watch the successful share rise without needing hotter particles.

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Progress

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Starter track

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Rates and Equilibrium

Dynamic Equilibrium / Le Chatelier's Principle is what this track opens next.

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