Volume of 1 gram of water?
1 kilo water = 1 liter water
1 gram water = 1 milliliter water
Depends on the substance. A gram of lead will have a lot less than a ml of volume, while a gram of oxygen will have a greater volume than 1 ml. Water is 1 ml per gram, but that changes with the temperature of the water. Warm water, and very cold water (<4o C) will have a somewhat greater volume than 1 ml per gram weight.
The mass = its volume. This is true if the mass of water is measured in grams and the volume is measured in cc and the density of water is 1 gram/cc. Depending on temperature, 1 gram/cc is a good approximation. In general, the relationship between water (or anything else) and its volume is mass/volume = density.