Why do all chemical reactions need energy to get started?

Answer 1

The "certain amount of energy" you're referring to is typically called "activation energy."

To explain why a chemical reaction would "need" to have an activation energy, you could use an example of a living organism, for example a human. There's reactions involved in your metabolism that convert the food you eat into energy to allow you to move your arms and legs, to breathe in and out, or even something so important as keeping your heart beating. If these reactions didn't have an activation energy, you could expect yourself to literally "burn up" as any food you eat would be uncontrollably converted into energy.

There's two main controls to any chemical process: mass transfer control and kinetic control. Mass transfer control comes into play with things like if you didn't chew your food, it would be more difficult for your stomach/intestines to break down and absorb the food, so the reactions to metabolise your food are slowed. Kinetic control is related to activation energy, as described above, where given that all the reactants are present for a given reaction, e.g. metabolizing your food, the reaction needs to happen at a certain rate to sustain life.

As a fun connection, reaction kinetics can be related to the temperature of the environment in which the reaction takes place, which gives you an idea of why it's so important for your body to stay around 98.6 degrees Fahrenheit. That crappy feeling you get when you have a fever comes from all the reactions in your body that depend on a certain reaction rate being upset by the increase in temperature.

Answer 2

If they didn't, you would be dealing with decomposed starting materials as they were too reactive. Many reactions can be carried out at room temperature while stirred in solution. Also, I don't think this statement holds true for all reactions in applicative sense (i.e. may get energy from light etc). Think about adding strong acid and base, or an alkali metal to water. These happen very readily and liberate heat from the reaction (exothermic).

Answer 3

During a chemical reaction breaking of the older bonds and formation of the new bondstakes place,the energy is require to break down the bonds of reactants either products are most stable than reactants or not,this energy corresponds to Activation energy.