Controlling+Chemical+Reactions

​ media type="custom" key="6202879" __Table of Contents__ - Activation Energy - Exothermic and Endothermic Reactions - Surface Area - Temperature - Concentration - Catalyst - Inhibitors __ Energy and Reactions __
 * Energy and Reactions​
 * Rates of a chemical Reaction
 * Activation Energy
 * Exothermic and Endothermic Reactions

__ Activation Energy __

Activation energy is the smallest amount of energy a chemical reaction needs to start. A reaction won't occur if the reactants don't have enough energy. "Energy is used to break chemical bonds of the reactants then, atoms begin to form new chemical bonds of the product" (Frank, Little, and Miller 67). Activation energy is important in a chemical reaction because chemical reactions need a certain amount of activation energy to start. "Activation energy is the difference between the energy of the reactants and the maximum" (Activation). "Activation energy is often supplied to a reaction mixture in the form of heat, but sometimes chemical reactions can happen suddenly by bringing the reactants together" (Activation)

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__Exothermic and Endothermic Reactions__

As it says above, every chemical reaction needs activation energy to start, but whether the reaction needs more energy from the environment or not depends on what kind of chemical reaction it is. It could either be an exothermic or endothermic reaction. "An exothermic reaction is a reaction that releases energy in the form of heat" (Frank, Little, and Miller 53). The burning of fuel is an exothermic reaction. The picture below of burning wood is an example of and exothermic reaction. The burning of natural gases and oil are also exothermic reactions. "An endothermic reaction is a reaction when energy is absorbed" (Frank, Little, and Miller 52). This kind of reaction can be an increase in temperature or a decrease in temperature. For example, if you mix baking soda and vinegar, it would be a decrease in temperature because it's taking heat away from it and it would feel cool instead of warm. Another example is when you fry an egg. The temperature would increase because of the heat being added as the egg cooks.



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__Rates of Chemical Reactions__
 * Surface Area
 * Temperature
 * Concentration
 * Catalyst
 * Inhibitors

__Rates of Chemical Reactions__

Chemical reactions don't occur at the same time. Some reactions are very fast while others can be very slow. For example, explosions occur very quickly and the rusting of metal occur very slowly. Depending on the conditions, a reation can happen at different rates. " To make a chemical reaction happen faster, you need to get more reactant particles together more often and with more energy and to slow down a reaction, you need less reactant particles" (Frank, Little, and Miller 69). The rate of a reaction can be changed by its surface area, temperature, and concentration. That can be done by using substances called catalysts and inhibitors.



__Surface Area__

By changing the surface area, the rate of a reaction can be changed. "When a solid substance reacts with a gas or a liquid, only the particles on the surface of the solid come into contact with the other reactants" (Frank, Little, and Miller 69). If you break the solid down into smaller pieces, more particles will be exposed and the reaction will happen faster. Speeding up a reaction like this can be dangerous sometimes, but other times, increasing the surface area can be useful.

__Temperature__

The rate of a reaction can also be increased by changing the temperature. When a substance heats up, particles will move faster. Fast moving particles increase the rate of a reaction in two ways. " One way is the particles come in contact more often which means there is a greater chance for a reaction to happen" (Frank, Little, and Miller 70). "Another way is faster moving particles have more energy" (Frank, Little, and Miller 70). More energy makes makes more particles of the reactants to become greater than the activation energy. When you reduce the temperature, the reaction will slow down.

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__Concentration__

If you increase the concentration of the reactants, then the rate of the reaction will also increase. "Concentration is the amount of a substance in a given volume" (Frank, Little, and Miller 70). An example would be when you put a small spoonful of sugar into a glass of lemonade, that would make it sweet, but when you put a large spoonful of sugar, it will make it sweeter. The glass with more sugar will have a higher concentration than the glass with a little sugar. When you increase the concentration of the reactants it adds more particles to react.

__Catalyst__

"A catalyst is a material that increases the rate of a reaction by lowering the activation energy" (Frank, Little, and Miller 71). Catalysts are not reactants because they only affect a reactions rate, but they are not permanently changed by a reaction. Our body has cells that contain biological catalysts called enzymes. We have thousands of different enzymes in our body. There are also catalysis. "A catalysis is a process in which a substance increases the speed of a chemical reaction without being consumed by the reaction" (Catalysis). There are two types of catalysis, homogeneous and heterogeneous. "In homogeneous catalysis, the catalyst and the reactants are in the same physical state and heterogeneous catalysis involves two physical states" (Catalysis). Heterogeneous catalysis are used in industries because they can be seperated from the products of the reaction and be reused again.

__Inhibitors__

"An inhibitor is a material used to decrease the rate of a reaction" (Frank, Little, and Miller 71). Some reactions are more useful when they can be slowed down instead of speeded up. Inhibitors prevent reactants from coming together. They can combine with one of the reactants permanently or temporarily.

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