Viscosity Adhesion and Cohesion Ch 8 3 What

Viscosity, Adhesion, and Cohesion Ch 8. 3

What is Viscosity? • Viscosity is the RESISTANCE of a fluid to flow. Syrup has a high viscosity (it is very viscous!) • The shape and attraction of particles in a liquid determines how easily it will flow. • The flow rate of a liquid is the speed at which the liquid flows from one point to another.

Flow Rate • Which liquid has the faster flow rate? Oil Vs. Honey

How Does Temperature Affect Viscosity? • Liquids: – When liquids are heated, viscosity decreases – Particles move faster and space out – Less friction and less attraction – Liquid flows more easily

How Does Temperature Affect Viscosity? • Gases: – When gases are heated, viscosity increases WHY? ? ? – Particles move faster and collide with each other – More collisions = more friction – Gas flows with more resistance

Adhesion • Ever noticed how a little water sticks to the glass after you’ve emptied the glass? Some fluids are attracted to surfaces or other fluids. . .

Adhesion = sticking to something! Adhesion is the attraction of two different objects or fluids to each other.

Cohesion • Cohesion is the ability of particles to attract each other. s ule lec ther! o r m ch o e t a Wa act e r att • Example: water particles attract other water particles at the surface

Cohesion • The cohesion of water molecules at the surface creates “surface tension”. Surface tension allows the surface to act like a “skin”

Freeze! “High 5” Reading Check • How is flow rate related to viscosity? • What is the effect of temperature on viscosity in liquids? In gases? • What is the difference between adhesion and cohesion?