Hello and welcome back for the second podcast for Unit 15 where we're going to be discussing factors that can actually speed up a reaction rate and that's what we want to look at here is how we can actually speed reactions up and make them go as fast as we possibly can make them because that is going to be in our best interest over time. The first factor we want to look at is increasing the concentration for solutions. If we increase the concentration of a solution will increase the amount of our chances of having collisions and overall will speed up the reaction rate. This is an example that happens a lot. Like if we have something that has a higher concentration of acid, it's going to dissolve something a lot faster or corrode a metal a lot faster than if we had something of low concentration where we'd see it actually slow down a lot.
Other concentrations of this are having something like a high concentration of acid. that's high in oxygen concentration versus pure air. If we had a higher oxygen concentration, we'd actually have something burning a lot faster. And we can see evidence of this in watching the movie Apollo 13. In that movie, there was an actual accident involving high oxygen concentration. So if you could watch this clip and you'll see what happens.
Between Jack's back taxes and the Fred Hayes show. I'd say that was a pretty successful broadcast. Thank you very much, Houston. We've got a couple of housekeeping procedures for you.
We'd like you to roll right to 060. Did all your rates? Roger that. Rolling right. 060. And if you could give your oxygen tanks a stir.
Roger that. Hey, we've got a problem here. What did you do?
Nothing, I speared the tanks. Whoa! Hey, this is Houston. Say again, please. Houston, we have a problem.
Alright, so there you have it. A higher oxygen concentration actually caused there to be an explosion in the ship, and... Fortunately, in that scene, which was a real life story, all the crew members did survive that accident.
But an example of a place where you have a higher oxygen concentration causing a much faster reaction. The second factor that we want to talk about is an increase in surface area. And if you actually have a substance that's crushed or shaved down into smaller pieces, It's going to react a lot faster than if you have it in its block form. An example of this would be to look at something like sugar cubes and see that they're going to be slower to dissolve than when you have powdered sugar, which is going to dissolve fast. There's a lot more points of contact over here for other molecules to collide with.
than it would be in a case where it's in its block form and you can't get to all those places in the middle. More surface area over here on the powdered side, it's going to dissolve faster. A place where we can see a very fast reaction occur due to surface area is in a grain elevator. And when a grain elevator explodes, which does happen from time to time, even in this day and age, it is because of an increase in surface area for...
powdered grain itself. Typically what can happen is these can be very devastating and damaging as you can see on this building here. This area had a very bad grain explosion due to the surface area increase and how these occur is What will happen is over time moisture will build up in here and cause the grain to actually clump together and form air pockets inside. And when those air pockets form and you have those clumps, what people will do in some cases to actually get them to fall down is they will bang the sides with a shovel or some other instrument.
And if that metal actually causes a spark to occur and the surface area increases on the powdered particles, they'll actually be able to be engulfed in flames. I will be showing you a demonstration of this in class. And you see a very intense explosion.
As you can see, it's pretty powerful, as I had said before, as the whole side of this building blew out. Looking at it a little closer, that's going through a concrete wall that was reinforced. And it is a very fast reaction due to the increase in surface area. Third factor.
is an increase in temperature. If we increase the temperature of a substance, we're going to increase the kinetic energy and the speed at which that substance is moving, which is going to be able to have more collisions occur just because of that speed increasing, and that's going to speed up the reaction. If you've ever seen bread dough before that's been frozen, over time the reaction that occurs to make the bread dough itself rise is slowed down enough that it's not able to occur.
And because of that, the bread dough itself does not rise. The minute that it actually set out room temperature, its reaction does occur and it will speed up that reaction and cause it to expand and rise. So then you can bake it. And basically, if you don't have that temperature, it's not going to occur.
So that's the third factor, temperature. Now the fourth factor is a little bit different from the other three that we've had. We also have catalysts that occur. And that's not actually part of the reaction itself. It's actually separate from it all.
But what it does is it lowers the activation energy within the reaction. And there's specific catalysts that are going to be used for specific reactions. You don't have a particular catalyst that can be used for every single reaction.
In a lot of cases, what they'll use is certain metals to produce certain reactions to occur a lot faster and lower the activation energy. You'll also see other things as well and other examples. I'll talk to you in a minute about that.
But you just want to realize that an uncatalyzed reaction has a certain amount of activation energy that is required to actually get over the hump. If you add a catalyst to that reaction, it will lower it in a lot of cases significantly and give it much less of a hump to actually climb over to make that reaction occur. And therefore, it is going to speed up how fast that reaction does occur.
So that's the basic principle of a catalyst. And an example of a catalyst, most of you are starting to drive now. All cars. About 20 years ago, we're mandated to actually have what's called the catalytic converter placed onto them. And the reason for this is because what in theory was being produced from cars when gasoline was burned was carbon dioxide and water.
And that, as we know before from a typical combustion reaction, is the products that are formed. And what was happening is in addition to that, they found that there were other pollutants being formed, things like NO and it could be any amount of oxygen. So it's always referred to as NOx or NOx gases that were being formed and that is a form of pollutant.
And the reason for that is because when those NOx gases react with water, What they were forming was nitric acid and we would get things like acid rain from this. And that was one thing they wanted to actually prevent from occurring. So what they made was a metal catalyst inside of the cars that would instead take this NOx and by adding the catalyst. would break these down into safer nitrogen and oxygen gases. And basically by placing this into the car to actually have that emit, they would have much safer air coming out of cars and reduce the pollution factor.
And where they're placed on the car is right here in between your engine and the... about the middle of the exhaust pipe is where the catalytic converter is before it actually goes out of your muffler and has much cleaner gases because of it. And this is what one looks like.
It's a little boxy piece. Inside it has metals typically either made of palladium or platinum that are there to catalyze the reaction and break down those NOx gases into nitrogen and oxygen gas. And that is one example of a catalyst that lowers the activation energy and causes that to occur.
Another example would be enzymes that you've probably heard of before when you were in biology for digestion. If we didn't have digestive enzymes, it would really slow down the digestive process, and we would only eat, you know, even up to every couple days because of how long food would... take to digest through our bodies. So having those catalysts actually causes us to need to eat more and speeds up the reaction of the digestive process to keep us moving at a better pace. Now in addition to catalysts as a factor to speed up a reaction, we also have things that are the opposite as well.
And those are items that we can place in and increase the activation energy. and slow down the rate of reaction, those are inhibitors. Inhibitors will slow down the rate of reaction, and we want that in some cases, especially with things like food, where we don't want it to spoil. So they place preservatives in the food to actually have this occur. And that's basically it for the factors that affect reaction rates.
So if you have any questions, please ask. Otherwise, don't forget to write your podcast question, and we'll see you in class.