A substance which take part in a reaction

The substance which take part in chemical reaction are called Reactants ..

Chemical reactions are usually characterized by a chemical change . A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products..

Reactants means that a substance that takes part in and undergoes change during a reaction.

Some chemical reactions go to completion, resulting in all of the reactants becoming products. These reactions are said to be irreversible. 

(Hope this helps) Sky

8 m/s because for him to get the same amount of energy as ray is putting out, bobby, who weighs half as much as ray, needs to run twice as fast.

i don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.