The phase change in which a substance changes from a soild toa gas or vapor without changing to a liquid first is

SUBLIMATION

is the phase change in which a substance changes from a solid to a gas or vapor without changing to a liquid first. When a gas or vapor changes directly into a solid without first changing to a liquid, the phase change is called deposition.

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.