Having trouble understanding ways of speeding up chemical reactions in your chemistry homework? Generally, there are four methods: catalysts, concentration, change in temperature or change in pressure. Remember these four C's and you'll be good to go!
Background of Chemical Reactions
Chemical reactions take place when a set of reactants combine to yield a set of products. It can be visualized in this diagram:
A + B --> C + D
Essentially, A and B represent the reactants while C and D represent the products that are produced from the reaction. Just remember that there can be more than two reactants and two products.
The rate at which chemical reactions occur is important to know. Some chemical reactions take a very long time to happen while others can happen instantly. So the rate of chemical reactions is somewhat based on the chemical properties of the reactants.
Another thing to keep in mind is the collision theory. The collision theory states that for a reaction to occur, its molecular reactants must collide with each other. When these reactants reach a particular point with their collisions, the chemical reaction occurs and yields its products. The particular point the reactants must reach is called the activation energy. Keep in mind that the activation energy varies in terms of what reactants are colliding with each other.
One of the first ways to speed up a reaction is with the use of catalysts. Remember that the reactants of a chemical reaction must reach a particular activation energy level in order for the reaction to occur. In order to make certain reactions occur faster, catalysts can be used.
Catalysts work by lowering the activation energy level that the reactants must reach in order for a reaction to occur. Since the reactants have to reach a lower activation energy level, the reaction rate itself is increased.
Another thing to note is that catalysts are not necessarily used in the reaction. We know that reactants react to form products, yet the catalysts themselves do not have to convert into products. This is partly because catalysts are not included in the reactions. It is almost magic that catalysts can remain the same; however, this is not always the case.
Another method for speeding up reactions is the amount of concentration in the reactants. If there are more concentrations of reactants in a system, it makes sense that these reactants have a higher chance of colliding with each other and this creates the possibility of the chemical reaction happening much faster.
Let's say you want to add lemon juice to your glass of water. If you add just a little bit of lemon juice and stir it, it takes awhile for the lemon juice to mix in with the water. However, if you add more concentration of lemon juice to the water, it mixes in faster. Even though this isn't a true chemical reaction, it illustrates the concept because the higher concentration of lemon juice allows the drink to be mixed more quickly.
Temperature and Pressure
Falling in line with the collision theory, temperature and pressure are two more ways to speed up a chemical reaction. In theory, the higher the temperature, the faster the reactant molecules will move. Because these molecules are moving faster, they have a better chance of colliding with each other and producing the chemical reaction.
Like temperature, pressure is also important because it can restrict the space in which the reactant molecules move. The higher the pressure, the less space the molecules have to move, which also increases the probability that they will collide. For example, if you increase the pressure of a gas, the gas molecules are limited to a confined space and have a higher probability of reacting if the right reactants are in place.
- "Reaction Rates." http://www.chem4kids.com/files/react_rates.html
Abhijit Tembhekar. "Yellow Lemons." http://commons.wikimedia.org/wiki/File:Yellow_lemons.jpg
"Low Temperature Oxidation Catalyst." NASA Langley Research Center. http://commons.wikimedia.org/wiki/File:Low_Temperature_Oxidation_Catalyst.jpeg