<h2>Reaction rates and collision theory</h2>
<p>It should be clear now that the average rate of a reaction varies depending on a <a data-lesson="atomic-and-atomic-mass-number" data-subject="chemistry" data-tutorial="chemistry-essential-ideas" href="https://app.ulearngo.com/chemistry/chemistry-essential-ideas/atomic-and-atomic-mass-number">number</a> of factors. But how can we explain why <a data-lesson="reactions-2" data-subject="chemistry" data-tutorial="metals-metalloids-nonmetals" href="https://app.ulearngo.com/chemistry/metals-metalloids-nonmetals/reactions-2">reactions</a> take place at different speeds under different conditions? <strong>Collision theory</strong> is used to explain the rate of a reaction.</p>
<p>For a reaction to occur, the <a data-lesson="the-kinetic-theory-of-gases" data-subject="chemistry" data-tutorial="states-of-matter" href="https://app.ulearngo.com/chemistry/states-of-matter/the-kinetic-theory-of-gases">particles</a> that are reacting must collide with one another. Only a fraction of all the collisions that take place actually cause a chemical change. These are called <em>successful</em> or <em>effective</em> collisions.</p>
<div class="ns-school-emp">
<h3>Definition: Collision theory</h3>
<div class="ns-school-defn">
<p>Reactant particles must collide with the correct <a data-lesson="energy" data-subject="chemistry" data-tutorial="thermochemistry" href="https://app.ulearngo.com/chemistry/thermochemistry/energy">energy</a> and orientation for the reactants to <a data-lesson="chemistry-104-summary-1" data-subject="chemistry" data-tutorial="physical-and-chemical-change" href="https://app.ulearngo.com/chemistry/physical-and-chemical-change/chemistry-104-summary-1">change</a> into products.</p>
</div>
</div>
<p>Collision theory explains how chemical reactions occur and why reaction rates differ for different reactions. It states that for a reaction to occur the reactant particles must:</p>
<ul>
<li>
<p>collide</p>
</li>
<li>
<p>have enough energy</p>
</li>
<li>
<p>have the right orientation at the moment of impact</p>
</li>
</ul>
<p>These <em>successful collisions</em> are necessary to break the existing bonds (in the reactants) and form new bonds (in the products).</p>
<div class="ns-school-emp">
<h2>Optional Activity: Collision Theory</h2>
<div class="ns-school-defn">
<section class="activity">
<h3>Aim</h3>
<p>To determine the best way to approach your friend, in <a data-lesson="bond-order" data-subject="chemistry" data-tutorial="covalent-bonding-continued" href="https://app.ulearngo.com/chemistry/covalent-bonding-continued/bond-order">order</a> to link your <strong>right</strong> arm with their <strong>left</strong> arm.</p>
</section><section class="activity">
<h3>Method</h3>
<p>Try different ways of approaching your friend:</p>
<ul>
<li>
<p>back to back</p>
<img alt="91a18bf1e3446f60e56d8029becd8bc0.png" src="https://data.ulearngo.com/assets/06284d18-2573-4cd7-8f5d-fd564d6e2b1c"/></li>
<li>
<p>front to back</p>
<img alt="bd24ad0820c861416cfcc19a5159bf85.png" src="https://data.ulearngo.com/assets/73571909-378e-4cd1-9f5c-be64063420dd"/></li>
<li>
<p>side to front</p>
<img alt="c4b772a86909b18689a443eee761a8de.png" src="https://data.ulearngo.com/assets/591b9d34-e871-4fb8-82ea-400e2bd6e99a"/></li>
<li>
<p>side to side</p>
<img alt="65e307acc55ee96eb56a3ff08ff4c55b.png" src="https://data.ulearngo.com/assets/6697afe0-2616-4c3c-944b-a723e4c4b3d4"/></li>
<li>
<p>front to front</p>
<img alt="fba5b8dc7abbe15d4f43560f189e99c6.png" src="https://data.ulearngo.com/assets/a64a69cd-c9bf-48c7-aae2-5441e4648a4c"/></li>
<li>
<p>etc</p>
</li>
</ul>
</section>
<section class="activity">
<h3>Results</h3>
<p>Determine how hard it is to link arms in each of these positions.</p>
</section>
<section class="activity">
<h3>Discussion</h3>
<p>If you approach your friend from behind (facing their back) it is hard to link arms. Approaching from their left (sideways so that your right side is on their left), it is easy to link up.</p>
</section>
<section class="activity">
<h3>Conclusion</h3>
<p>You should have found that each method had a different level of difficulty for linking arms. This is similar to how molecules (compounds) approach in a reaction. The different ways you approached your friend represent the different orientations of the molecules. The correct orientation makes successful collisions possible.</p>
</section>
</div>
</div>
<section class="activity"></section>
<section class="activity">
<p> </p>
</section>
<section></section>

1da7dde6-444c-4cfc-9055-98f781c809ca

Reaction Rates and Collision Theory

Chemistry generally explores the substances of which matter is composed, the investigation of their properties and reactions, and the use of such reactions to form new substances. 

Chemistry

Discover the causes of energy changes in chemical reactions, explore exothermic and endothermic reactions, and learn about factors affecting reaction rates in this tutorial.


Reaction Rates and Collision Theory

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