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Homogeneous and Heterogeneous
Mixtures
2
Homogeneous mixtures
(solutions)
• a solution is a solute
that is dissolved in a
solvent
• an aqueous solution
is a solute that is
dissolved in a water
3
Parts of a Solution
• solute – the part
of a solution that
is being dissolved
(usually the lesser
amount)
• solvent – the part
of a solution that
dissolves the
solute (usually
the greater
amount)
• solute + solvent =
solution
Solute Solvent
Example
solid
solid
metal alloy
solid
liquid
salt water
gas
solid
Hg in Ag?
liquid
liquid
alcohol and water
gas
liquid
carbonated water
gas
gas
air
• most ionic compounds (+/-) and polar covalent
molecules (+/-) dissolve readily in water (+/-)
(“like disolves like”)
– solvation: ions (+/-) break away (dissociate) from
the crystal and surrounded by water molecules (+/-)
• nonpolar covalent molecules (Ø) such as oil,
grease, fuels, do NOT dissociate in water (+/-)
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5
C12H22O11(s)
H2O

C12H22O11(aq)
dissolve
NaCl(s)

dissociate
Na+(aq)
+ Cl-(aq)
Electrolytes
• because ions (+/-) are in a solution, they
can conduct electricity
• the electric current can travel on the
mobile charges
– the more solute dissolved in the solution, the
better the conduction of electricity
• HCl, MgCl2, and NaCl are strong
electrolytes.
– they dissociate (break apart) almost completely
into ions.
• compounds that do not conduct electricity
are nonelectrolytes
– insoluble molecular compounds (Ø) that do not
break apart into ions
» many carbon compounds, sugar, alcohol
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7
8
Electrolytes in the Body
 Carry messages to
and from the brain
as electrical signals
 Maintain cellular
function with the
correct
concentrations
electrolytes
Make your own
50-70 g sugar
One liter of warm water
Pinch of salt
200ml of sugar free fruit
squash
Mix, cool and drink
9
Heterogeneous Aqueous Systems
• suspensions
–a mixture from which particle settle out
upon standing
–particles are larger (1000 nm) that in a
solution and cannot stay suspended like
they can in a solution (1nm)
–examples: flour in water, clay in water
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• colloids
–particles (1nm-1000nm)do not settle out
and therefore have cloudy appearance if
concentrated
–examples: glue, gelatin, paint, smoke
–particles will scatter light which is called
the Tyndall effect
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• under a microscope, can see the
movement of the particles (Brownian
motion)
–these collisions prevent the particles
from settling
http://images.google.com/imgres?imgurl=http://myweb.tiscali.co.uk/nickpower/w
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http://www.inventioneeringco.com/commentaryfiles/brownian_motion.swf
http://video.google.com/videosearch?sourceid=navclient&rlz=1T4SUNA_enUS316US316&
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