Which of the following best describes what happens to the substance between t4 and t5?

(a) the molecules are leaving the liquid phase.
(b) the solid and liquid phases coexist in the equilibrium.
(c) the vapor pressure of the substance is decreasing.
(d) the average intermolecular distance is decreasing.
(e) the temperature of the substance is increasing.

Between the temperature points and , the molecules are leaving the liquid phase.

Explanation:

Reading the conversion of states of matter through a graphical representation; we can easily see that the matter is converting from the liquid phase to gaseous phase respective to the temperatures to .

As the solid is heated at a constant rate at 1 atm pressure, it changes its state from solid to liquid and then liquid to gas consistently.

As the matter crosses the temperature , it leaves it's liquid phase and starts transforming into its gaseous version. It's quite obvious that the temperature will go on increasing until the matter reaches its gaseous state.

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.