[student8607]

Generally speaking, with a phase diagram how is:
the melting point
the boiling point
the triple point
the critical point

affected when temperature is raised at a constant pressure?

affected when pressure is raised at a constant temperature?

[student8607]

Found a little snippet of info:
increase pressure, decrease melting point
increase pressure, increase boiling point

increase temp, melting point increases
increase temp, decrease boiling point

But I'm still really confused at what all of this means.
Increase/decreases how? Up/down, left/right?

[ARGOS++]

Dear student8607;

Maybe you must first learn what the lines in the Phase Diagram means/represents:

http://en.wikipedia.org/wiki/Phase_diagram

Then it should be much easier for you to answer your questions.

Good Luck!
                    ARGOS⁺⁺

[student8607]

Yeah I did check out Wikipedia earlier but (to my surprise) didn't find the article very helpful with the basics.
Sure I understand the definitions of critical and triple point but don't get the reasoning behind the phase changes.

Here goes nothing:
If increase pressure (with + slope) :
melting point increases because particles forced closer together (liquid form)
boiling point decreases for same reason

if increase temp:
melting point increases: solids "melt" in the sun
boiling point increases also


How close am I?

Triple/critical points 

[ARGOS++]

Dear student8607;

Did you read the legend to the first simple Phase Diagram?
What is the red line?    What is the blue line?  What is the green line?

And here one hint: The triple point got its name, because it’s the only point (Temp/Pressure) where three phases coexist!

Good Luck!
                    ARGOS⁺⁺

[student8607]

"The green lines mark the freezing point and the blue line the boiling point, showing how they vary with pressure."

So in this diagram as P increases:
boiling point and melting point both increase

...

[ARGOS++]

Dear student8607;

Correct!

But there is nothing like a dependency of pressure from pressure, or temperature from temperature.
There is only a dependency of temperature (Freezing point/Boiling point/etc.) on pressure or visa versa.

And the critical point is the upper endpoint of all Boiling points, and what’s that meaning?

Good Luck!
                    ARGOS⁺⁺