how dose the scientist know the substances goes through a change of state during the time period labeled B on the graph?

The temperature remains constant

Explanation:

In a plot of temperature against time, it is easy to spot the points on the graph where a change of state is taking place.

During a change of state, the temperature does not not change with time. These are points that are plateaus on the temperature-time graph.

This is because, during phase change, the heat that is added is used in breaking intermolecular forces therefore a temperature change is not observed until the phase change is complete.

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.

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.