When wax is heated, it turns into a liquid. how are the wax molecules affected by this change of state?
a. the molecules gain energy.
b. the molecules lose energy.
c. the molecules move closer to one another.
d. the space between the molecules increases.
e. the space between the molecules decreases.

This question has two correct options, these are OPTION A AND OPTION D.

Wax is a solid substance and its molecules are tightly packed together. When wax is heated, the molecules of wax gains kinetic energy and move about randomly until the inter molecular forces binding them together is broken and the wax turn into liquid. In the liquid state, the molecules have more free movement, so they spread out and the distances between them increase. Thus, when wax is heated, its molecules will have more kinetic energy to overcome the inter molecular bond in the solid and the distances between the molecules increase in the liquid state.

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.

there is none because earth is stationary and flat.