Its arbitrary. It was developed on the greek phoenetic system and never reallybwas explained.
Write procedural steps that allow you to demonstrate the sun's role in the water cycle using common material - for each explain what you are modeling and how the materials you have chosen represent nature.
Using the accepted value for the volume of 1 gram of water at the temperature of the room that you reported above, what is the accepted value for the density of water
5.75 Grams per cm^3
You do mass divided by volume
