The answer to that depends on the density of the substance in question.
For instance the volume of 68 grams of Lead would be smaller than the volume of an equivalent mass of gaseous hydrogen.
Without restricting the volume, any number of properly sized (volume) metals can weigh 68 grams.
mass is to grams
The mass of 40 grams is 40 grams and the volume of 20mL is, wait for it, ... 20 mL!
Grams is NOT a unit of volume. It is a unit of weight or mass.
Mass per volume Mass in grams volume in cubic centimeters
Mass per volume Mass in grams volume in cubic centimeters
the mass is the 50 grams you probably need the volume volume = mass / density get the density from tables
Density = mass/volume, so:36 grams/ 12 milliliters3 grams/ milliliter
Mass per volume Mass in grams volume in cubic centimeters
Mass and volume use different units of measure. Mass uses grams as a unit of measurement; however 1000 grams equals 1 kilogram. Volume is measure by liters.
Converting volume (mL) to mass (grams) requires the ratio of the subtance's mass to volume (its density, in other words).
Density = Mass/Volume = 30/15 = 2 grams per millilitre.