Catalysts Speed It Up

A catalyst is like adding a bit of magic to a reaction. Reactions need a certain amount of energy in order to happen. If they don't have it, oh well, the reaction probably can't happen. A catalyst lowers the amount of energy needed so that a reaction can happen more easily. A catalyst is about energy. It doesn't have to be another moelcule. If you fill a room with hydrogen gas (H₂) and oxygen gas (O₂), very little will happen. If you light a match in that room (or just produce a spark), most of the hydrogen and oxygen will combine to create water molecules (H₂O). It is an explosive reaction.

The energy needed to make a reaction happen is called the activation energy. As everything moves around, energy is needed. The energy that a reaction needs is usually in the form of heat. When a catalyst is added, something special happens. Maybe a molecule shift ... Read more »

Equilibrium Basics

Equilibrium is a pretty easy topic - big name, but easy idea. First, when you have a system made up of a bunch of molecules, those molecules sometimes combine. That's the idea of a chemical reaction. Second, a chemical reaction sometimes starts at one point and moves to another. Now imagine the reaction finished and you have a pile of new chemicals. Guess what? Some of those chemicals want to go through a reverse chemical reaction and become the original molecules again. We don't know why. Sometimes they just do.

Put those two ideas together and you have equilibrium:
1. Two reactants combine to make a product.
2. Products like to break apart and turn back into the reactants.

There is a point where those two reactions happen and you can't tell that any reactions are happening. That's the point when the reaction looks like it is finished. In reality, some of the molecules are turning into products and some are turning back into reactants. You need to imagine that you're as small as a molecule and you're ... Read more »

Rate of Reaction

The rate of a reaction is the speed at which a reaction happens. If a reaction has a low rate, that means the molecules combine at a slower speed than a reaction with a high rate. Some reactions take hundreds, maybe even thousands, of years while others can happen in less than one second. The rate of reaction depends on the type of molecules that are combining. If you want to think of a very slow reaction, think about how long it took dinosaur bones to become fossils through breakdown. You can thank chemical processes in bacteria for most of those dinosaur bones in the museum.

There is another big idea for rates of reaction called collision theory. The collision theory says that as more collisions in a system occur, there will be more combinations of molecules bouncing into each other. If there are a higher number of collisions in a system, more combinations of molecules can occur. The reaction will go faster and the rate of that reaction will be higher. Even though they are both liquids, think about how slowly molecules move in honey whe ... Read more »

Chemical Reactions

Let's start with the idea of a reaction. In chemistry, a reaction happens when two or more molecules interact and the molecules change. That's it. What molecules are they? How do they interact? What happens? The possibilities are infinite. When you are trying to understand reactions, imagine that you are working with the atoms. Imagine the building blocks are right in front of you on the table, instead of billions of reactions in your beaker. Sometimes we do this using our chemistry toys to help us visualize the movement of the atoms. There are a few key points you should know about chemical reactions:

1. A chemical change must occur. You start with one compound and turn it into another. That's an example of a chemical change. A steel garbage can rusting is a chemical reaction. That rusting happens because the iron (Fe) in the metal combines with oxygen (O₂) in the atmosphere. When a refrigerator or air conditioner cools the air, there is no reaction between the air molecules. The change in temperature is a physical change. ... Read more »