In the number 5.008 g how many significant figures are there?

There are 4 significant figures.

Rules for sig figs:

Rule 1: Non-zero digits are always significant.
Rule 2: Any zeros between two significant digits are significant.
Rule 3: A final zero or trailing zeros in the decimal portion ONLY are significant.

You can find more in depth explanations about these rules here: http://chemistry.bd.psu.edu/jircitano/sigfigs.html

When the fluid cools, the kinetic energy of the molecules decreases. This causes the molecules to slow down and move closer together. Since the molecules are closer together, the density of the fluid increases and the fluid sinks.

they were correct :) ..

points