100 ml is a volume. It is not a weight!
Depending on the density of the material is smaller, bigger or equal to 100g. (100g @ density = 1,0 kg/dm3)
If you want to measure a certain volume, you need to do this with a volume measuring device, not with a weigh/scale.
Or, you know the density of the material and can calculate the volume (liter) = weight (kg) / density (kg/ Liter)