A cup of water weighs 236.59 grams, and a cup of butter weighs 226.72 grams. This is assuming that a cup of butter weighs 8 ounces. Grams are a measure of mass, and cups are a measure of volume.
Different substances possess different densities. By observing the masses of a cup of water and butter, it can be deduced that water is more dense than butter. Water carries more mass per unit of volume than butter. A cup of sugar has a mass of 127.53 grams while a cup of bread flour has a mass of 136.02 grams.
Mass is defined as the weight of an object within the Earth's gravitational field. The mass of a cup of water is the same on the Earth and on the Moon. However, a cup of water has a heavier weight on the Earth than it does on the Moon.