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Reaction Rates Factors 18,464 views

Teacher/Instructor Kendal Orenstein
Kendal Orenstein

Rutger's University
M.Ed., Columbia Teachers College

Kendal founded an academic coaching company in Washington D.C. and teaches in local area schools. In her spare time she loves to explore new places.

There are several factors that affect reaction rates. Their effects can be explained using collision theory. These factors are the nature of the reactants, concentration, surface area, temperature and catalysts. Each of these factors increases reaction rate because they increase the number or energy of collisions.

Alright so we can have reactions that happen instantly and we can have reactions that happen over millions and millions of years. So what is it that affects the actual reaction of rate, the how faster a reaction can go. Well there're 5 main things that are going to affect how fast a reaction is going to be able to go. There's the nature of the reactants, since sometimes they just inherit within the whatever the reactants are and how fast or so they go. Larger metals tend to react faster because they have a very low ionization energy meaning that they can get rid of those electrons very easily and they have a very high shielding effect so the electrons, electrons are able to react very quickly, whereas if it's a smaller molecule they have been held in much more tightly within the nucleus. So and the nature of the reactants themselves actually play a major part in how fast or slow a reaction takes place.

The second thing that might take, that actually does affect the reaction rates is concentration. So we know that from the collision theory the particles actually need to collide in order for the reaction to occur. So the more particles you have, the higher concentration that you have, the more collisions that you're going to have with the reactants and the products and the reaction is going to go faster. So higher concentrated materials will react much faster than diluted materials, just because that they're more of them, more reactants than there're and they're able to collide easier. And the third thing is surface area, so if you have a more surface area in your reactants, they have actually more reactants exposed. So they're able to react quicker, so if you think about like let's just something dissolves it's actually much easier.

Let's talk about a sugar cube versus a granule of sugar, if you were to dumb those equally into some water it's easier for the granule sugar to dissolve, rather than the cubed sugar. Just because there's more reaction sites within the granule of sugar exposed than the cubed sugar. So the larger the surface area the faster the reaction will actually take place. The fourth thing we're going to talk about is, that affects reaction rates is temperature. So as we increase temperature, we're increasing kinetic energy, those particles are actually moving faster and they're colliding with each other in a, more often and more frequently. So if we're going to, if we increase temperature we're going to increase the reaction rate and actually this is approximation but for every 10 Kelvin or 10 degrees Celsius that we increase the heat actually the rate of reaction will then double. So that's how much temperature affects the rate of reaction.

And the last thing that actually affects reaction rates or how quick a reaction takes place are catalysts. You might know them from Biology as enzymes, they actually increase the reaction rate without being consumed, they actually just change the reaction pathway and in Chemistry we're going to call the reaction mechanism which we'll get in at another video. The opposite thing that slows it down are called inhibitors, they're things that actually slow a reaction down which are actually desirable as well if you don't want a reaction to occur. Sometimes inhibitors will actually cease reaction completely. So these are the 5 main things that affect how fast or slow a reaction will take place.