The term you're looking for is heat capacity. Water has a much higher specific heat capacity (on a per unit of mass basis) than most other everyday materials, and it comprises most of the mass of a pot+water [+pasta] system being heated, so the time and energy required to boil won't be changed significantly by the presence or absence of the pasta.

maybe not? if the water and pasta are at the same temp to start with. I'm assuming heating pasta also takes less energy that heating water.