couple theory questions i don't quite understand...

What is vapor pressure ad why does it change with temperature?

and...

The assumption was made that slight changes in the depth under the surface of the water will not significantly change total pressure in a graduated cylinder. Comment on the validity of this assumption.

any help is appreciated. :-)

For vapor pressure see this site.

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

Under some conditions the last statement problem is true and it may not be true under other conditions. The context of the question is very important.