In order to separate water into the elements of hydrogen and oxygen, a chemical change must take place. This suggests that water is: a) an element b) a pure substance c) a mixture D) heterogeneous

D

Explanation:

heterogeneous

.of or denoting a process involving substances in different phases (solid, liquid, or gaseous).

in scientific notation, the value of the  speed of light in a vacuum

  will be written as 2.995 * 10^8. when this value is represented in the form of

  a * 10^b, then, a = 2.995 and b = 8.

the value of the speed of light in a vacuum given above can also be rounded up to approximately 300000000. in this case, the scientific notation will be written as 3 *10^8.

i believe the answer is three water molecules