Complete the sentences to explain what’s happening at different portions of the heating curve.

particles of the substance have the most kinetic energy when the substance is( the part of the graph that represents where the substance has the least amount of potential energy is labeled(

multiple choice answers available.
(a)
1. a gas
2. a solid
3. melting
4. vaporizing

(b)
1. solid
2. vaporizing
3. melting
4.liquid
5.gas

Particles of the substance have the most kinetic energy when the substance is(a)1. A gas. The part of the graph that represents where the substance has the least amount of potential energy is labeled(b)1. Solid.

Gas molecules have the highest average velocities among the three states of matter so gas has the highest kinetic energy. During freezing, a substance loses a lot of potential energy so solid has the least potential energy.

increased stability in the completion of fluorine's outer shell.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.