How is suspense created in the film you watched in class?

In my class we watched 'what lies beneath' . we was told to list 3 examples of what happens in the scene and what makes it suspenseful.

Example 1 : when the women claire picked up the phone to check if her husband had in fact called 911 it turns out that he had instead called 441 . she stands in front of the mirror to our surprise. he come up behind her with a cloth with some sort of chemical on it and suffocates her this leads to her body becoming weak as she tries to escape. we see her loose al sense of her legs and not move them as she looses control of her bodies muscles and movement.

Example 2: there was a random times flashes of the 'copses' through out the film how ever the one which i found most suspenseful was when claire went in to the bathroom and the water was running and all we could see was the tap running then she looks at the tub filled with water. we scream due to the fact we see a visual corpses of the dead student.

Example 3:she escapes from the house due to the fact her husband tried to kill her and them she gets in the wrong car. she swaps cars then and then begins to drive away then we see the her husband at the back of the car this scares us.