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

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Liquids have a permanent network

of intermolecular bonds that are

continuously made and broken

liquids hold together

liquids can flow

4 16.4 Physical Properties of Liquids

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

5 16.4 Physical Properties of Liquids

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.

6 16.4 Physical Properties of Liquids

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

7 16.4 Physical Properties of Liquids

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

8 16.4 Physical Properties of Liquids

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

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Cohesion

Cohesion keeps rain drops together as they fall on the ground

Liquid mercury (Hg) is very cohesive

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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

11 16.4 Physical Properties of Liquids

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

12 16.4 Physical Properties of Liquids

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

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Cohesion or adhesion?

Water is more adhesiveIt sticks to the sides of the glass

Mercury is more cohesiveIt sticks to itself more

Meniscus

14 16.4 Physical Properties of Liquids

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

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Cohesion

Adhesion

Viscosity

Physical properties

The resistance of a liquid to flow under an applied force

Honey

16 16.4 Physical Properties of Liquids

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.

17 16.4 Physical Properties of Liquids

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

18 16.4 Physical Properties of Liquids

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

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Cohesion

Adhesion

Viscosity

Surface tension

Physical properties

A property of liquids to resist having their surface broken

20 16.4 Physical Properties of Liquids

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.

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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

22 16.4 Physical Properties of Liquids

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: