# Measuring volume: Solid vs Liquid/Gas

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1. Jun 14, 2016

### ElijahRockers

I was just curious... what is the practical reason behind having two separate units for measuring volume? For instance, we can use cubic centimeters and mL interchangeably in practical medicine, i.e. injections. But we tend to use cubic (centi)meters for solids, and liters for liquids/gasses.

Why don't we measure all volume by the same unit? That is, why don't we measure the volume of an gold ingot in terms of liters? Or perhaps the volume of a bucket of water in cubic meters?

2. Jun 14, 2016

### Staff: Mentor

Not sure what your question is.

mL and cubic centimeter are the same thing (historically I believe they were not, but they are now). Yes, we use liters for liquid volumes and cm3 but these days that's just a meaningless convention.

Using cubic meter for everything would be impractical.

3. Jun 14, 2016

### ElijahRockers

We have a single property, volume, measured in different ways depending on the phase of the substance. We measure solids with cubed distances, and fluids with liters. I am trying to get some insight as to the reason things are done this way. Are there any particular historical reasons? Practical reasons? etc. etc....

What about liters? Is there anything impractical about measuring the volume of a solid in terms of liters?

4. Jun 14, 2016

### Staff: Mentor

Check wikipedia article on liter, it explains where the difference came from.

As I said, mL and cm3 are now perfectly equivalent, and we just by convention use mL (and L) for volumes of things that are not solid and can be poured.

5. Jun 15, 2016

### Kevin McHugh

What difference does it make? There are mks units and cgs units. Conversion to the units you wants is one calculation away. Personally, I like mks units, but physicists like cgs units.