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Properties of Liquids

Objectives:

    1.    Define viscosity and surface tension.

    2.    Explain the relationship of viscosity and surface tension to intermolecular forces.

    3.    Describe some of the usual properties of water and relate those properties to hydrogen bonding.

Key Terms:

    viscosity    surface tension

Notes: (14-2)

The phase of any substance is determined by the inter and intramolecular forces.  
Most liquids are made of molecules therefore their intramolecular forces are covalent in nature.  
The intermolecular forces determine the physical properties of the liquid.

 

Viscosity

Viscosity is a term used to describe the fluid friction (resistance to flow) within a fluid.  The amount of viscosity is completely dependant on the amount and strength of the intermolecular bonds.  

Substances with large amounts of H bonds are very viscous
Temperature and viscosity are inversely related (low temp = high viscosity)

image(www.process-heating.com/PH/ FILES/IMAGES/63214.jpg)

Kinematic Viscosity(www.process-heating.com/PH/ FILES/IMAGES/9560.gif)

Surface Tension

Surface tension is the downward (toward the middle) force that a fluid exerts on its surface molecules.  It is responsible for giving drops their round appearance.  The rules governing surface tension are the same as for viscosity.

Substances with large amounts of H bonds have high surface tensions
Temperature and surface tension are inversely related (low temp = high surface tension)
Surface tension determines the boiling point of a liquid

"surface tension"(www.kibron.com/Science/ tension-1.gif)

water strider

 

(home.att.net/~larvalbugrex/ strider.jpg)

 

 

 

 

(www.cascade-earth.com/Web%20Photos/ Water-Drop.jpg)

Other "Unusual" Properties of Water

Extremely high boiling point - due to its shape 
Can absorb great amounts of heat without a great increase in temp.
The density in solid form is less than its liquid phase
Very high surface tension
Very high heat of vaporization (boiling point)
Is the universal solvent

 

 

 

 

 

 

Last modified: March 12, 2003