Homogeneous and Heterogeneous Mixtures

1

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 2

• •

Parts of a Solution

solute – the part of a solution that is being dissolved (usually the lesser amount)

Solute Solvent

solid solid

Example

metal alloy solid liquid salt water solvent – the part of a solution that dissolves the solute (usually the greater amount) gas liquid gas solid liquid liquid Hg in Ag?

alcohol and water carbonated water

•

solute + solvent = solution gas gas air 3

•

most ionic compounds (+/-) and polar covalent molecules (+/-) dissolve readily in water (+/-) (“like disolves like”) 4

–

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 (+/-)

C 12 H 22 O 11 (s) H 2 O



C 12 H 22 O 11 (aq) NaCl(s) dissolve



Na + (aq) dissociate + Cl (aq) 5

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, MgCl

2 , and NaCl are strong

– 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

6

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

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 9

•

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 10

•

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 eb content/pmkscience.jpg&imgrefurl=http://myweb.tiscali.co.uk/nickpower/web content/chempmf.html&usg=__cs0ZXoClwOslcgDq4pzTBp36Rsk=&h=240&w=30 0&sz=22&hl=en&start=12&um=1&tbnid=NokxbmlM2Sy2hM:&tbnh=93&tbnw=116 &prev=/images%3Fq%3Dbrownian%2Bmotion%2Banimation%26hl%3Den%26rlz %3D1T4SUNA_enUS316US316%26um%3D1 http://www.inventioneeringco.com/commentary files/brownian_motion.swf

http://video.google.com/videosearch?sourceid=navclient&rlz=1T4SUNA_enUS316US316& q=brownian%20motion&um=1&ie=UTF-8&sa=N&hl=en&tab=wv# 11

12