1. Viscosity, Adhesion, and Cohesion
Ch 8.3

2. Syrup has a high viscosity (it is very viscous!)
What is Viscosity?
Viscosity is the RESISTANCE of a fluid to flow.
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.
Syrup has a high viscosity (it is very viscous!)

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

4. 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

5. 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

6. 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...

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

8. Water molecules attract each other!
Cohesion
Cohesion is the ability of particles to attract each other.
Example: water particles attract other water particles at the surface
Water molecules attract each other!

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

10. 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?