The scientific instruments that measure the volume of a gas, liquid, or solid are called volumeters. They include graduated cylinders, syringes, beakers, and volumenometers. These instruments range from the very simple to the complex. The simple instruments, such as the graduated cylinder, involve no more than a glass cup with measuring marks listed on the surface. The volumenometer, on the other hand, works by displacement--measuring the volume of another substance to get at the volume of the original substance.
Quite familiar to school children, the graduated cylinder is simply a long tube with tic marks running along the side that measure different volumes in milliliters or ounces of liquids, such as water or a liquid solution. A base is attached to the bottom of the tube to improve stability. To measure volume, pour the liquid into the graduated cylinder and observe what tic mark the top of the liquid reaches. This is its volume.
A syringe measures volume in a similar fashion to a graduated cylinder. The syringe is a small tube with a plunger and needle attached to either side. Tic marks run the length of the tube indicating different volume measurements. In blood work, for example, a nurse draws blood from a vein with a syringe. The tic marks on the side of the syringe indicate the volume of the blood that has been drawn.
A beaker looks like a large cup with a semi-spout on the lip. This semi-spout eases pouring. The beaker measures liquids when they are poured into it. Many kinds of liquids can be used, including water, detergent, or even smoothies. Tic marks on the side of the beaker show what the volume of the liquid is. Beakers are convenient for measuring the volumes of solids as well. To determine the volume of the solid, fill a beaker with a liquid substance, note its volume, then drop a solid in the beaker. The difference between the new height of the liquid and the old indicates the volume of the solid.
A volumenometer is a complicated device for measuring the volume of an irregularly shaped solid, such as germinating seeds or small roots. Simple solids, such as wood blocks with linear dimensions, can be measured by taking their height, width, and length, and multiplying. An irregular object, however, cannot be. Volumenometers come in various designs, but most use liquid mercury to indirectly measure the volume of the object. The change in volume of the liquid mercury indicates the volume of the object.