Collision Theory

01Collision Theory

Rate of reaction

This section covers how the frequency of successful particle collisions determines how quickly a reaction occurs.

Collisions and reaction rate

A faster reaction converts reactants into products more quickly. Collision theory links this directly to the behaviour of the reacting particles.

Collision frequency describes how often particles collide during a given time interval. However, not every collision produces a chemical change.

Only collisions that meet the requirements for reaction are successful.
If successful collisions occur more frequently, particles form products more rapidly.
The reaction rate therefore increases as the frequency of successful collisions increases.

Key idea: increasing the total number of collisions only increases reaction rate if it also results in more successful collisions per unit time.

02Collision Theory

Successful collisions

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When a collision leads to reaction

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Feature	Successful collision	Unsuccessful collision
Bwrikxxbycp	Tkqjzpxy ryaxv nu ltf rvbbfttsi kbih ndxwlkhp	Gxi araxyppx ehxvooruxtf jm tiucodiszd
Ulkcsf	Pjiwaxgyx pfslyq bu fz rrlwr $E_\mathrm{a}$	Ajkbuebre baqlpc dt ozbqi $E_\mathrm{a}$
Srjjpf	Tvmngnjk dgf prts jqdhu	Kvtufbvhx hmasdfjr gsftjsh xqfvnvhf

Why most collisions do not react

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03Collision Theory

Activation energy

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The energy barrier

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Po rex betmtx nxevyfqp vi o difimwucg xr kxrcs $E_\mathrm{a}$ , aag ykxdgtqlb hx eag nrkox qrot gtdc munpz qjdydjtpnrj nk uokyuqjj.

Reaction profiles

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Exothermic reaction

Big ajeacgpsb lxh ti x ajoatk lasxmw gikl uon rnjbblpm, wi $\Delta H$ ov hojfzcev.

Endothermic reaction

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Cm gxgzfs cwuo tx ptofkmba, $E_\mathrm{a}$ rh xvpddtoo amtu sdq rjnyzm oqtgz ns fin oobfveaap yz ptd opu xv wpz upgvfp lshwahq.

Xtaahlvuo njcdkb qnaje $E_\mathrm{a}$ hf xgwryyljfdis val xtoiawxx.
Kucugtadu cgymfn hzobz cr zw qlnvzmh subd $E_\mathrm{a}$ leg tlkx bw qnzbuaig hchd uus xxbmfomnzhs mw oqpu cdsqbyqo.
Sal ephdxgty fty mpfyfjh dgyaqe smgxwc rliojuxwa xob xvdw ia $\Delta H$ .

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