Rates of reaction

What is a reaction?

A reaction happens when reactants turn into products. There are many factors that affect the speed at which this happens.

Collision Theory
Reactions only take place when the particles of the reactants come together with the right energy and orientation. The smallest amount of energy needed for a reaction to happen is called the activation energy. Reactions are more likely to happen if we increase the chance of reacting particles colliding with each other or if we increase the energy that the particles have when they collide.

Temperature
When we heat a substance, energy is transferred to its particles. This means the particles move faster, if they move faster then they collide more often. Simple.

Particles that move quicker have more energy, this means that a higher proportion of the particles have energy greater than the activation energy.

Catalysts
Catalysts allow reactions to happen at a lower activation energy. This means that more particles will have this minimum energy and reactions happen faster.

Surface area
Increasing the surface area of a substance means that there are more particles available for a reaction to take place - this means collisions are much more frequent.

Concentration
Increasing the concentration of a substance increases the rate of reaction - this is because you have more particles in a given area for collisions to happen. If you have twice the concentration then you have twice the number of particles. This would double the reaction rate - or form twice the product.