Properties of Liquids

Surface Tension

property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules

Surface Tension

Cohesive and Net inward Forces

Cohesive Forces

"generic" term for Intermolecular forces

Cohesive forces between liquid molecules

It is responsible for the phenomenon of surface tension

Water molecules on the surface of the water

These water molecules exhibit stronger attractive forces because they have no neighboring molecules above

(*At the surface, though, the outmost layer of molecules has fewer molecules to cling to and, therefore compensates by establishing stronger bonds with its neighbors, leading to the formation of the surface tension)*

Net Inward Force

A molecule on the surface of the liquid, there will be a net inward force since there will be no attractive force acting from above. This inward net force causes the molecules on the surface to contract and to resist being stretched or broken.

Viscosity

a measure of liquid's consistency or resistance to flow

Relatioship between IMF & Viscosity

Direct relationship (the greater the intermolecular forces, the more viscous the substance)

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WHY *? there are more atoms that can attract to one another (IMF), contributing to the substance's total attractive forces*

Vapor Pressure

the equilibrium pressure of a vapor above its liquid or solid state

Evaporation and condensation

occurs at the liquid surface

Relationship between temperature and vapor pressure

Direct relationship (increasing temperature increases the rate of evaporation and increases vapor pressure)

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WHY? *Since kinetic energy increases with temperature, molecules tend to have more energy to go into the gas phase.*

Equilibrium

the state at which when the evaporation rate equals condensation rate

Vapor Pressure

Molecules in the liquid can go into the gas phase easily if intermolecular forces among them are weak.

Major Heat of Vaporization

The amount of heat required to turn a substance from liquid into a gas (steam) at a constant T and P

Major Heat of Vaporization

If intermolecular forces are strong, high energy input is needed and the liquid will boil at a high temperature.

Water at room temperature

pure water is a colorless, ordorless, and tasteless liquid

At 0 C

water turns to ice

At 100 C,

water bcomes a gas (steam)

Water’s characteristics

water has a bent shape, with two partially positive hydrogen atoms and a partially negative oxygen atom

Water’s bent shape

two partially positive hydrogen atoms and a partially negative oxygen arises because of repulsion between the electron pairs in the oxygen hydrogen bonds

Density

Relationship with buoyancy: Objects with a higher density than the other matter they are placed on will sink, while objects with a lower density will float.

Water molecules in ice

have a more defined hexagonal arrangement

Density

When melting point is reached, the rigid open structure breaks down. As a result, molecules can move closer together, making liquid water denser than ice.

High heat capacity

A property of water that means that it retains heat for a long time relative to the air.

Breezes

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