do not break bonds
This is a chemical reaction.
Photosynthesis
Most definitely.
It depends: just try to relate, try to write a chemical equation for and see if there are byproducts. Most likely, if the same chemical still has its same properties After the reaction, a chemical reaction has not occurred.
For most chemical reactions, energy is required to supply an "activation energy" required before reaction.
The speed of the reaction is most changed by enzyme activity, as enzymes can greatly accelerate the rate at which chemical reactions occur by lowering the activation energy required for the reaction to proceed.
The most important: to have the reactants !
An endothermic reaction is one that consumes heat.
Oxygen as most reactions have it although it could also be hydrogen
A chemical reaction that transfers energy from the reactants to the surroundings is referred to as an exothermic reaction. A reaction that takes energy in is endothermic.
Chemical reaction
Combustion is a chemical reaction.