物理化學難題, 連老師都唔知 -.- 快幫忙~

1. The flat region marked "?" shows saturated vapour and liquid in equilibrium.

In this region, a reduction in volume doesn't increase the pressure as more vapour is condensed to become liquid. At the (left) end of this region, when all vapour has condensed to liquid, a reduction in volume causes a rapid increase in the pressure of liquid because liquid is almost imcompressible.

2. Many substances exhibit the property shown on the given P-V diagram. Water is an example.