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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) |
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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 |
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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 |