Mass, weight and volume are mathematical and scientific quantities used to describe objects in space. Often, the aforementioned terms -- especially mass and weight -- are used interchangeably to mean the same thing, though they mean very different things. That they are different, however, doesn't mean they aren't directly related. In fact, if you know one of the above two values of an object, you can then calculate the third value using mathematical equations.
Mass refers to the amount of matter that an object -- whether liquid, gas or solid -- contains. It's generally measured in kilograms and grams, and it's a constant quantity that doesn't change, regardless of where an object resides. In particular, an object's mass remains the same whether it's on the moon, on Earth, on Saturday or even if it's just floating through space. In addition, mass is independent of size, meaning that though a bowling ball and soccer ball are about the same size, the bowling bowl has a greater mass.
Weight refers to the pull of gravity on an object. Because gravity changes throughout the solar system from planet to planet, an object weight's doesn't remain constant. For instance, someone who weighs 185 lbs. on Earth would weigh 68.45 lbs. on Mercury and 432.9 lbs. on Jupiter. This is because gravity and weight are directly related, in that as the force of gravity increases or decreases, so does an object's weight.
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Volume refers to the amount of space that an object takes up. Liquid volumes are measured in literals or milliliters; solid volumes are measured in meters cubed or centimeters cubed -- both of which are equal. To measure a solid object's volume, scientists place the object in a container of water and then measure how many milliliters it displaces. They then convert that to centimeters cubed using the equation 1 mL = 1 cm^3.
Weight, or W, is a product of mass or M and gravity or G, which leads to the following equation: W = M & G. In addition, mass and volume -- V -- are related by density or D, which measures the mass of a substance per unit volume via the following equation: D = M/V. Using the above equations, volume and mass can then be related by the following equation: V = (W/G)/D.