1. Properties of Liquids, Suspensions and Colloidal Dispersions

2. Three States of Matter
Solids contain particles that are extremely close together
Gases contain particles that are extremely far apart
Liquids lie in between the extremes of solids and gases

4. General Properties of Liquids

5. Incompressible and have a definite volume
Under normal conditions a liquid maintains its volume under pressure
an example of this property is the application of liquids in hydraulic systems:
braking system of a motor vehicle
garage hoist

6. Viscosity A liquid’s resistance to its flow
caused by an internal frictional force between adjacent layers of the flowing liquid

7. Surface Tension
Surface tension, a force, is a resistance of a liquid to an increase in its surface area
Arises from the attractive forces between the liquid’s molecules on and below the surface of the liquid
Causes water to form spherical droplets
Spheres minimize the ratio of surface area to volume
Allows some insects to “walk” on water
Surface tension of the water’s surface is greater than the weight of the insect
Can float a paper clip on water’s surface also
As with the insect mg < Fst

8. surface tension

9. Capillary Action
Capillary action is the spontaneous rising of of a liquid in a narrow tube
Capillary action of a liquid is due to the interaction between the cohesive forces within the liquid and the adhesive forces between the liquid and the walls of the tube
The narrower the tube, the higher the liquid will rise
See the next slide

11. Capillary Action and the Meniscus
The meniscus is the shape of the surface of the liquid when in a tube or cylinder.
It can be concave or convex, depending on the liquid.
Water
Forms a concave meniscus
The adhesive forces between the water and the surface are greater than the cohesive forces within the water

12. Capillary Action and the Meniscus
Mercury
Forms a convex meniscus
The cohesive forces within mercury are greater that the adhesive forces between the mercury and the surface
See the next slide of water and mercury in separate graduated cylinders

13. water forms
a concave
meniscus
mercury forms a
convex meniscus

14. Physical and Thermal Properties of Water
Property
Value
Density
1000 kg/m3
mass of one cubic metre of water at 277 K
Boiling Point
373 K
Transition temperature between liquid and gas
Freezing Point
273 K
Transition temperature between liquid and solid
Heat Capacity
75.2 kJ/mol/K
Heat required to raise one mole of water one Kelvin
Heat of Fusion
5.98 kJ/mol
Heat absorbed or given off in the solid phase/liquid phase transition
Heat of Vaporization
40.5 kJ/mol
Heat absorbed or given off in the gas phase/liquid phase transition
Thermal Conductivity
0.58 J/(s.m.K)
Rate of heat flow through water at 293 K

15. Physical and Thermal Properties of Water
Property
Value
Compressibility
4.9×10−10/Pa
Rate of change of volume per change in pressure.
Surface Tension
72.8 mN/m
This is the force/metre required to overcome the surface tension of water at 293 K.
Note: Surface tension of water decreases as temperature increases.
Viscosity
1.13 cSt (at 289 K)
The viscosity of a fluid is measured as (force × distance)÷(area × velocity)
This value is centipoise, the most common measure for viscosity.
Note: Viscosity decreases as temperature increases

16. Various Mixtures: Solutions, Suspensions, and Colloids

17. Mixtures in General
Mixtures are matter containing two or more substances
Mixtures can be homogeneous (uniform throughout)
Solutions are homogeneous
Mixtures can be heterogeneous (without uniform composition)
Suspensions and colloids are heterogeneous

18. Solutions: Some Definitions and Concepts
Solutions are made up of a solute and a solvent
the solute – least abundant compound in the solution
the solvent – most abundant compound in the solution
The solute and solvent can be in relative variable amounts
Any acid solutions can be highly concentrated or quite dilute
The solute and solvent may be in the same phase or different phases
soft drinks are a mixture of a gas (solute) and liquid (solvent)

19. Solutions and their Properties
Homogeneous mixture
Dissolved solute is ionic or molecular in size (0.1 to 1.0 nm)
Transparent and can be clear or coloured
Solute does not settle out with time
Solute passes through all filters
Solute and solvent can be separated by physical means such as evaporation
Light passes through the solution with no scattering

20. Examples of Solutions, Liquid or Otherwise
Ionic solutions (solid solute in water) such as
acids: HCl, H2SO4, CH3COOH
bases: NaOH, Mg(OH)2
aqueous salts: NaCl, AgNO3, Ca3(PO4)2
ionic solutions are examples of a solid solute in a liquid solvent
antifreeze (liquid solute in liquid solvent)
soft drinks (gas solute in a liquid solvent)
metal alloys (solid solute in a solid solvent)

21. Suspensions and their Properties
Heterogeneous mixture of solid particles in either a liquid or gas
Dissolved solute particles are greater than 100 nm
The mixture is cloudy
The solute settles out with time
Solute can be filtered with filter paper
Particles are large enough to block light rays impinging on the mixture

22. Examples of Suspensions
Oil and vinegar
Muddy water
Dust in air

23. Colloids and their Properties
Heterogeneous mixture of solid particles in either a liquid or gas
Dissolved solute particles are between 1 nm and 100 nm
Mixture is cloudy
Particles do not separate out with time
Solute can be filtered with a micro-filter
Particles are large enough to scatter light passing through the mixture but not block it completely

24. Types of Colloids and Examples of Each
Aerosols (solids in a gas): fog, clouds, smoke
Foams (gas in a solid): styrofoam, whipped cream
Sol (solid in a liquid): shampoo, ink, paint
Emulsion (liquid in a liquid): milk, lotion