1 Mixtures Day 1: Chapter 14 Lake Nyos, Cameroon Courtesy of George Kling, page

Mixture 2 or more substances 2 or more substances physically physically combined. combined.

Two Types: Homogeneous Homogeneous Same throughout Heterogeneous Heterogeneous Different throughout

Homogeneous? Homogeneous? Heterogeneous? Heterogeneous? Mixture

Heterogeneous Mixtures Suspension: two or more substances that do NOT mix Insoluble

Suspensions a mixture appears a mixture appears uniform when shaken. uniform when shaken. Particles Settle out Particles Settle out Need to shake or stir Need to shake or stir Ex. orange juice, salad dressing Ex. orange juice, salad dressing

SUSPENSION

WHY? “LIKES DISSOLVES LIKES” Polar AND Nonpolar : NOT MIX - Two substances only go together if they are alike. If they aren’t alike NOT go together. - Ex. Wax (nonpolar) and water (polar)

Polarity A molecule is polar when electrons are shared unequally. Have a (+) and (-) end A molecule is polar when electrons are shared unequally. Have a (+) and (-) end Molecules are nonpolar when electrons are shared equally between atoms Molecules are nonpolar when electrons are shared equally between atoms Water is very polar Water is very polar

Solution: Homogeneous Mixtures homogeneous mixture of 2 or more substances uniformly spread throughout a medium. homogeneous mixture of 2 or more substances uniformly spread throughout a medium.

12 Some Definitions A solution is a HOMOGENEOUS mixture of 2 or more substances in a single phase. One constituent is usually regarded as the SOLVENT and the others as SOLUTES.

Why Mix Uniformly? “Likes dissolve likes” “Likes dissolve likes” D6 C30 D6 C30 Polar dissolves in polar or Nonpolar dissolves in nonpolar Uses: dry cleaning

Microscopic Composition Demo: ethanol/water Demo: ethanol/water

15Colloid

Colloid Many types: we will look at one EMULSIONS Do not settle out or dissolve HOMOGENEOUS, HOMOGENEOUS, Opaque, not let light through

Likes Dissolve Likes How do we get two thing that are NOT alike to go together? How do we get two thing that are NOT alike to go together? Need Emulsifying Agent = third ingredient Need Emulsifying Agent = third ingredient Emulsifying agent is BOTH polar and nonpolar Emulsifying agent is BOTH polar and nonpolar

3. Emulsion a mixture where polar a mixture where polar substance is forced to mix uniformly with a nonpolar substance substance is forced to mix uniformly with a nonpolar substance Held together by emulsifying agent Held together by emulsifying agent Ex. mayonnaise, glue Ex. mayonnaise, glue

EMULSION

EMULSIFING AGENT Disk 10: Chapter 20 SOAPS AND DETERGENTS

SolutionsEmulsions(Colloid)Suspension UniformHomogeneous Don’t Settle out “Shake”Heterogeneous Transparent Light through Scatters Light Opaque Two or more phases Solute and solvent Alike (p/p or n/n) Emulsifying Agent Polar and nonpolar Polar with nonpolar LETS COMPARE mixtures

Mixture Properties & Particle Size Dispersed particles too big = suspension Dispersed particles too big = suspension Can filter out Dispersed particles small = solution Dispersed particles small = solution Pass through membrane

NoneTyndalleffectTyndalleffect nm Atoms, ions Small cules nm Largemolecules > 200nm Pass through Do NOT Pass through Throughmembrane Do NOT Pass through Do NOT Do NOT Pass through LIGHT SCATTERING PARTICLE SIZE FILTRATION DIALYSIS PropertySolutions Emulsions(Colloid) Suspension