Answers explained below in detail.
Explanation:
In general, notice how they show you how to find the current state of matter (phase) for CO2. That line shows that at the intersection of the temperature and pressure (think of it as a coordinate of (T, P)), it is resting on the line between solid and gas.
For question 1, it asks us to first examine what phase the CO2 would be at a certain pressure and temperature. Basically, just plot the coordinate. It is at -100 C, and 1 atm pressure. A file is attached for what this looks like. Where those two data points intersect is the current phase. That would be the solid phase at -100 C and 1 atm pressure. That's actually what dry ice is, solid CO2 :). Then, we go to room temperature. We now find the coordinate at the same pressure, but at room temperature, which is about 68 F, or 20 C. That point is also shown in the file. Notice that the intersection point is in the gas phase now. Going from a solid to a gas directly is called sublimation. That is what that smoke is that dry ice produces, essentially.
Unfortunately, since you didn't provide a phase diagram for water, you'll have to try the rest yourself.
For 5, though, the critical point is the point that ends the graph, shown in the file as well. Hope this helps.
