viscosity
The viscosity refers to the resistance of the fluid that appears when the form changes, or the property that the attached parts do not fall off. Though it is difficult to measure viscosity accurately, it takes more time for a viscous fluid to compare the time taken for the same amount of liquid to flow through a thin tube of the same thickness. At this time, it is possible to compare the viscosity by taking time with one liquid as a standard. Since viscosities usually decrease when the temperature rises, the temperature should be kept constant during the measurement. When using Ostbart's viscometer as the standard for water, the viscosity ratio of a liquid to water can be obtained by letting d and dw denote the density of each liquid, and the time t and tw that flow down between two scales of the viscometer . In a molecular liquid, a substance with a narrow temperature range, which is present in a liquid, is less viscous than a substance with a wide temperature range. In addition, the complex structure of the molecule is highly viscous. Water, alcohol and so on are different because of hydrogen bonding.