Topic: Properties of Liquids

1
Topic Properties of Liquids

• Do Now

2
Properties of Liquids

• Definite volume
• Indefinite shape
• Particles close together, but can move little bit
  
• Liquids can flow

3

• Density liquids much greater than gases
• Ex DH2O(l) is 1250x greater than
• DH2O(g) at 25?C (room temp)
• Liquids can be compressed but change in volume
  very slight requires enormous pressure

4

• Viscosity
• Surface Tensions
• Today we will learn about these physical
  properties

5
Viscosity

• Viscosity resistance to flow

6

• Viscosity depends on
• strength of IMF (force between molecules)
• sizes shapes of molecules
• temperature
• stronger the IMF, the higher the viscosity
• as temperature ?, viscosity ?
• as temperature ?, viscosity ?

7
Where does the marble drop fastest? Slowest?
water
glycerol
See demo (slide 10 of 13)
8

• engine oil prevents direct metal to metal contact
  
• thin film oil on surfaces prevents metal from
  flaking
• if oil too thick, wont circulate at low temps
• if oil too thin, will lose film strength at high
  temps

9
Surface Tension

• Particles at surface of liquid exist in
  unbalanced environment
• No attraction from above to balance attractions
  from below
• Surface seeks
• smallest possible area
• Net attractive force
• pulling down

DEMO
10
Surface Tension

• Surface Tension E required to ?surface area
• measure of inward pull
• Strong intermolecular attractions ?
• High surface tension

11
(No Transcript)
12
(No Transcript)
13
Washing with cold water The major reason for
using hot water for washing is that its surface
tension is lower and it is a better wetting
agent. But if the detergent lowers the surface
tension, the heating may be unnecessary.
14

• Increasing heat lowers temperature
• Compounds that lower surface tension of H2O are
  called SURFACTATS
• Disrupt hydrogen bonds between H2O molecules
• See video

15
(No Transcript)
16
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.
17
Soaps and detergents help the cleaning of
clothes by lowering the surface tension of the
water so that it more readily soaks into pores
and soiled areas.
18
Capillary Action

• Water forms concave meniscus in glass tube
• Attractive forces between water and glass is
  greater than attractive forces between water
  molecules
• Upward movement of liquid in narrow tube
  capillary action

19


Force(H2O-glass) ? Force(H2O- H2O)
Force(Hg-glass) ? Force(Hg-Hg)
Force(Hg-glass
CONVEX
CONCAVE meniscus
meniscus
20
(No Transcript)
21
(No Transcript)