Density measurement. To determine density of a solid (steel screw), first its volume is measured with a graduated cylinder using a displacement method. The cylinder is filled with colored water and its volume is recorded (35 mL, left panel). Then the screw is put in the cylinder and the new volume reading is taken (39 mL, center panel). The difference (4 mL) is the volume of the screw. The mass of the screw is measured separately using a small digital scale (29.5 g, right panel).