Fertilizers, synthetic or otherwise, are designed to provide plants with the raw ingredients necessary for growth. Fertilizers are usually a mix of the following ingredients (from wikipedia entry for fertilizers)

(Six macronutrients: nitrogen (N), phosphorus P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S);

seven micronutrients: boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn),molybdenum (Mo), and zinc (Zn).

The most important of these are Nitrogen, Phosphorus, and Potassium. In fact, fertilizers are typically described by their 'NPK' analysis, which describes the relative ratio of these key ingredients.

While these materials are necessary for the plant to survive, too much of any particular component can also have negative effects. Additionally, the soil pH (the acidity of the soil) can be lowered (made more acidic) with the addition of too much fertilizer, and limit plant growth.

It will die, same as with natural fertilizers.

If a soil has too much fertilizer it can kill the plant. Plants need the nutrients in their soil to be within a certain range in order to grow properly. Too high a concentration of nutrients can dehydrate or burn the plant.

Here is a project idea on "Do plants promote pesticide breakdown?