Open Ended Investigation – Energy Release Rates
Part 1 – Research
1. A combustion reaction involves the burning of a substance, usually in air, to produce heat and light energy. The actual rate at which a combustion reaction takes place depends on many factors; combustion reactions can occur in a slow, spontaneous or explosive rate. In a slow combustion reaction, there is not enough or a limited supply of oxygen and heat available to overcome the activation energy of the substance; resulting in the substance being combusted slowly. An example of a slow combustion reaction is the corrosion of iron; when iron is exposed to oxygen in a moist environment, rust (iron oxide) forms on the surface. A spontaneous reaction occurs on materials with low activation energy and on exposure to enough oxygen. An example of a spontaneous reaction is when white phosphorus reacts spontaneously with oxygen in the air to form phosphorus oxide. Lastly, an explosive reaction occurs very rapidly releasing heat and gas in a short amount of time. The material may have a high activation energy, and is usually initiated by a flame or spark. An example of an explosive reaction is in petrol engines of a motor vehicle; a spark is used to ignite the petrol with oxygen.
2. The collision between reactant particles is significantly important in determining the rate of reaction in any chemical reaction. Molecules must collide with a sufficient amount of energy to lead to a reaction; if not enough energy is acquired with the collisions of particles, no reaction will occur. When these reacting particles collide, enough kinetic energy is needed to overcome the activation energies and break the bonds. Once they are broken, new bonds will from in the product molecules. The rate of reaction also largely depends of the nature of the reactants and their activation energies. The higher the activation energies, the more collisions are needed to break the bonds, resulting in more energy needed. Though there are many factors which can increase the rate of collisions between reacting particles; by increasing the temperature, concentration, surface area of the reactants or by adding a catalyst; a faster rate of reaction will occur.
3. The main relationship between temperature, concentration and particle size of reactants is that when they are increased, a faster rate of reaction will occur as more collisions occur between the reactant. When increasing the temperature of a substance, the molecules move around much faster and therefore have greater kinetic energy. As a result, these molecules collide more frequently and with higher amount energy so that these collisions have a better chance of breaking the bonds and reacting quicker. When increasing the concentration of a substance; such as a solution, there are a greater number of solute particles to react with another substance. As there are more particles, there are more collisions between the reacting particles, resulting in a better percentage of successful collisions and a faster rate of reaction. When increasing the surface area of a solid substance, the surface is more exposed to reacting particles resulting in more collisions and a faster rate of reaction. Conversely, if you decrease the temperature, concentration and particle size of reactants, you slow the rate of reaction.
4. A catalyst is a substance that provides an alternative reaction pathway with a lower activation energy, when the reactants of a reaction come in contact with the substance. A catalyst is able to increase the rate of reaction by allowing a reaction to take place in such a way that less collision energy is needed. Catalysts are extremely important in an industrial aspect as they help make reactions possible that would normally be slow to complete and expensive as less energy is required to break the bonds of the reactants. An example of a catalyst used an industry is the manufacturing of ammonia which uses an iron...
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