Topic: Properties of Liquids

Do

Now:

Properties of Liquids1. Definite volume

2. Indefinite shape

3. Particles close together, but can move little bit

1. Liquids can flow

4. Density liquids much greater than gases

5. Liquids can be compressed but change in volume is only a small amount & requires enormous pressure

6. Have viscosity

Viscosity• Viscosity = resistance to flow

– Depends on:• strength of forces

between the liquid molecules

– Honey has stronger forces between its molecules compared to water; flows slower

• Temperature– If you heat up the honey, it will

flow quicker

Where does the marble drop fastest?

Slowest?

water

glycerol

See demo (slide 10 of 13)

Which substance has the greatest viscosity?

Which substance has the strongest forces between its molecules?glycerol

glycerol

• engine oil prevents direct metal to metal contact

• thin film oil on surfaces prevents metal from flaking

• if oil too thick, won’t circulate at low temps

• if oil too thin, will lose film strength at high temps

FYI: ENGINE OIL

Properties of Liquids1. Definite volume

2. Indefinite shape

3. Particles close together, but can move little bit

1. Liquids can flow

4. Density liquids much greater than gases

5. Liquids can be compressed but change in volume is only a small amount & requires enormous pressure

6. Have viscosity

7. Surface tension

Surface Tension

At the surface of a liquid, there are no liquid molecules above, so there is an imbalance of forces between the molecules

Thus the next attractive forces pull the liquid inward

DEMO

Surface tension is the amount of energy need to increase the surface area

• The stronger the forces between liquid molecules, the higher the surface tension

Liquid HgLiquid H2O

Has stronger forces between it’s molecules = greater surface

tension

Which has greater surface tension?

http://www.esb.utexas.edu/mabrybio211/chapter03/08-Surface-Tension-Water.jpg

Why use Hot Water when washing dishes?

• Increasing the temp. decreases the surface tension – meaning water can spread out = better wetting agent

• But if you use soap (it’s a surfactant, meaning it decreases the surface tension) so you don’t need the hot water

DON’T COPY

http://www.weeds.iastate.edu/reference/visuals/additives/img007.gif

Don't touch the tent!

Common tent materials are somewhat rainproof in that the surface tension of water will bridge the pores in the finely woven material. But if you touch the tent material with your finger, you break the surface tension and the rain will drip through.

DON’T COPY

Properties of Liquids1. Definite volume

2. Indefinite shape

3. Particles close together, but can move little bit

1. Liquids can flow

4. Density liquids much greater than gases

5. Liquids can be compressed but change in volume is only a small amount & requires enormous pressure

6. Have viscosity

7. Surface tension

8. Capillary Action

Capillary ActionCapillary Action = Attractive force between the liquid and the wall of the container.

If the force between the container and liquid is greater than the forces between the liquid molecules, the liquid will move up the tube forming a concave meniscus

Force(Hg-glass) Force(Hg-Hg)

Force(H2O-glass) Force(H2O- H2O)