The Effect of Changes in Temperature, Concentration and Surface Area on Rate of Reaction

The rate of a chemical reaction is affected by several factors, including temperature, concentration of reaction participants and surface area of solids involved.

Temperature:

Increasing the temperature in a chemical reaction increases the kinetic energy of the particles involved which makes them more likely to collide.
More frequent collisions increase the chance of a successful interaction between reacting particles, so the rate of reactions generally increases with temperature.
Additionally, particles at higher temperatures are more likely to have the necessary energy to overcome the activation energy of the reaction, which leads to an increased reaction rate.

Concentration:

Increasing the concentration of reactants in a solution generally increases the rate of reaction.
This is because more particles in the same volume results in more frequent collisions and thus an increased potential for reactions to occur.
However, this effect is curtailed when all the reactants are used up - at this point, increasing the concentration no longer influences the reaction rate.

Surface Area:

The larger the surface area of a solid reactant, the higher the rate of reaction.
If a solid reactant is broken down into smaller pieces or a powder, its surface area is increased. This provides more contact area for collisions with other reactant particles.
Therefore, grinding or crushing solids can effectively increase the reaction rate by increasing the surface area.
It should also be remembered that conditions that increase the number of successful collisions between reaction particles - such as higher temperature, higher concentration, and larger surface area - can result in a higher rate of reaction.
Make sure to understand the particle model of matter and collision theory behind these, as they form the basis of your understanding on how these factors influence the rate of reaction.