solids and liquids physical properties of liquids

Solids and Liquids

Physical Properties of

Liquids

2 16.4 Physical Properties of Liquids

Condensed matter:Atoms or molecules are closely packed and interact with each other

Atoms or molecules do not interact with each other, except for collisions


Liquids have a permanent network

of intermolecular bonds that are

continuously made and broken

liquids hold together

liquids can flow


flow: the ability of a liquid to move and change shape under a force, such as gravity.


On the molecular level, liquids are like amorphous solids.

Energy of solid vs. liquid

However, higher energy in liquids causes intermolecular bonds to break quickly after they are formed.


Quartz a crystalline form of SiO2

Glassan amorphous form of SiO2

Liquid SiO2 doesn’t remember whether it came from quartz or glass!

slow cooling fast cooling


Quartz a crystalline form of SiO2

Glassan amorphous form of SiO2

Liquid SiO2 doesn’t remember whether it came from quartz or glass!

melting melting


Cohesion

Physical properties

The property of a liquid that causes it to hold together

Attractive forces between

molecules in a liquid cause

liquid drops to come together as

tight as possible in a perfect sphere


Cohesion

Cohesion keeps rain drops together as they fall on the ground

Liquid mercury (Hg) is very cohesive


Cohesion

Adhesion

Physical properties

The property of a liquid that causes it to stick to surfaces

Geckos use the property of

adhesion to stick to surfaces such as the walls and ceilings of houses


Adhesion

When something is “wet,” we mean that liquid is adhering to it

Different surfaces have different wettability:

they can be wet by the same liquid differently


Adhesion

When something is “wet,” we mean that liquid is adhering to it

Different surfaces have different wettability:

they can be wet by the same liquid differently

Liquids that adhere to things very well are called adhesives

They are commonly used as glues or put onto tape to make it sticky


Cohesion or adhesion?

Water is more adhesiveIt sticks to the sides of the glass

Mercury is more cohesiveIt sticks to itself more

Meniscus


Plants use capillary

action

to draw water up from roots to

leaves.

Even very tall trees move

water this way.

Water passes through these tubes

capillary action: an effect where liquids is pulled up a thin tube by adhesion


Cohesion

Adhesion

Viscosity

Physical properties

The resistance of a liquid to flow under an applied force

Honey


Viscosity

Viscosity is a measure of resistance to flow.

Snails and slugs use mucus, a very viscous substance, to help them stick to surfaces and move.


Viscosity

Viscosity depends on the strength of intermolecular bonds

Water is a polar molecule with strong intermolecular forces.

Water is more viscous than nonpolar liquids, such as liquid nitrogen


Viscosity

Viscosity depends on the strength of intermolecular bondsthe shape of the molecules

Oils are more viscous because the long-chain molecules can be easily entangled, and this slows down the flow


Cohesion

Adhesion

Viscosity

Surface tension

Physical properties

A property of liquids to resist having their surface broken


surface tension: a property of liquids to resist having their surfaces broken, usually measured in J/m2.

Surface tension measures

the energy it takes to break the

surface of a liquid.


Surface tension

Soaps work by partially lowering surface tension

Soaps are medium-length chains with - one polar end - and one non-polar end

The polar end adsorbs to the

water surface, and this breaks up

the surface tension


Cohesion

Adhesion

Viscosity

Surface tension

Liquids have a permanent network of intermolecular bonds that are continuously made and broken

This results in interesting physical properties:

solids and liquids physical properties of liquids

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liquid cause liquid

liquid differentlyliquids

liquid differentlyadhesionwhen

nonpolar liquids

property of adhesion

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crystalline form of

lowering surface tensionsoaps