Question

Use collision theory to explain why reaction rates generally increase when the temperature increases.

Short answer

Using collision theory, reaction rates generally increase when temperature increases because the increase in temperature raises the kinetic energy of particles. This leads to them moving more rapidly and colliding more frequently, and more importantly, means more of these collisions have sufficient energy (activation energy) for a successful reaction. Thus, more successful reactions translate to an increased reaction rate.

Step-by-step solution

Understand Collision Theory

Collision theory postulates that for a reaction to occur, particles must collide with one another. Not just any collision will lead to a reaction, but it must be a successful one where particles collide with a certain minimum energy called the activation energy. The higher the frequency of successful collisions, the higher the rate of reaction.

Understand the Effect of Temperature on Kinetic Energy

Temperature is a measure of the average kinetic energy of particles in a substance. When the temperature increases, the kinetic energy of the particles also increases. Higher kinetic energy means particles move more rapidly, which leads to an increased number of collisions.

Relate the Effect of Temperature to Reaction Rates

Increased temperature leads to higher kinetic energy and more rapid movement of particles, the number of collisions per unit time will increase. More importantly, with increased energy, more of these collisions will have energy equal to or greater than the activation energy. This will lead to more successful collisions and thus an increased reaction rate. As such, the reaction rate generally increases when temperature increases.

Key concepts

Reaction Rates

Understanding reaction rates is crucial to many fields of science, particularly chemistry. A reaction rate defines how fast or slow a chemical reaction occurs. This rate can be influenced by various factors, such as the concentration of reactants, the presence of a catalyst, the surface area of solid reactants, and especially, temperature.

At the heart of this concept is the idea that for a chemical reaction to take place, reactive particles must collide. But not just any collision will suffice; they have to meet the criteria set by collision theory. To influence a reaction rate, one needs to alter the frequency and energy of these collisions, and that's precisely what changing the temperature does.

Activation Energy

Activation energy is the minimum quantity of energy that the reacting species must possess in order to undergo a specified reaction. Imagine activation energy as a barrier that reactants must overcome for a reaction to occur. Not all collisions are successful in translating into chemical reactions; only those with sufficient energy to surpass this energy barrier lead to product formation.

It's akin to a sprinter needing a certain amount of energy to leap over a hurdle; similarly, reactant particles must exert enough energy during their collision to lead to a reaction. Lowering the activation energy through the use of a catalyst, or increasing the kinetic energy of the particles (which is often achieved by raising temperature), can lead to higher reaction rates.

Kinetic Energy

Kinetic energy is the energy that an object possesses due to its motion. In the context of collision theory and chemistry, particles (atoms, molecules, or ions) have kinetic energy as they move and vibrate.

The kinetic energy of these particles affects how they collide, which is central to whether a reaction will take place or not. If the kinetic energy is too low, particles may not collide with enough force to overcome the activation energy. However, when the kinetic energy is high, particles collide more frequently and with enough energy to potentially initiate a reaction.

Effect of Temperature on Reaction Rate

Temperature plays a pivotal role in determining the reaction rate. As established, an increase in temperature generally leads to an increase in the kinetic energy of particles. This heightened movement means more frequent and more forceful collisions occur.

When collisions happen more energetically, they are more likely to surpass the activation energy threshold. Subsequently, you see an increase in reaction rates because there are a higher number of successful particle collisions. A practical example of this is cooking; by heating food, we speed up the reactions that cook it. In sum, higher temperatures usually mean faster reactions, thanks to increased kinetic energy leading to more successful collisions.