If you have a new question, ask an expert . The longer it takes, the more viscous the liquid. Another approach is to put the liquid in a funnel with a narrow spigot at the bottom, open the spigot and record the amount of time it takes for a specified quantity of the liquid to to flow through. Instruments known as viscosimeters are used for more formal measurements of viscosity. They may operate by measuring the flow of the liquid through an orifice of known size, similar to the approach described above.
Some viscosimeters cause a disk to rotate in the liquid.
The drag, or resistance to rotation, may be measured. The viscosity of a gas will, therefore, increase with temperature. Both molecular interchange and cohesion contribute to viscosity in liquids. The effect of increasing the temperature of a liquid is to reduce the cohesive forces while simultaneously increasing the rate of molecular interchange. The former effect tends to cause a decrease of shear stress, while the latter causes it to increase.