Polarity of Solvents Background Information for Soap Lab

Polarity of Solvents

Background Information for Soap Lab

A Hydrocarbon

• Typical petroleum product

• Non-polar

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 470

Oil and Water Don’t Mix

• Oil is nonpolar• Water is polar

“Like dissolves like”

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 470

Hydrogenation

Timberlake, Chemistry 7th Edition, page 570

+ H2

vegetable oils shortening stick margarine

tub (soft)margarine

Molecular Polarity

H–C–H

H

H–C–H

H–C–H

H–C–H

H

H H

O

nonpolar molecules: -- e– are shared equally-- tend to be symmetric

e.g., fats and oils

polar molecules: -- e– NOT shared equallye.g., water

“Like dissolves likeLike dissolves like.”polar + polar = solutionnonpolar + nonpolar = solutionpolar + nonpolar = suspension (won’t mix evenly)

Using Solubility Principles

C=CCl

ClCl

Cl

Chemicals used by body obey solubility principles.

-- fat-soluble vitamins: e.g., vits. A, D

Dry cleaning employs nonpolar liquids.-- polar liquids damage wool, silk

-- also, dry clean for stubborn stains (ink, rust, grease)-- tetrachloroethylene is in common use

-- water-soluble vitamins: e.g., vit. C

MODEL OF A SOAP MOLECULE

NONPOLARHYDROCARBON

TAIL

POLARHEAD

Na1+

emulsifying agent (emulsifier): -- molecules w/both a polar AND a nonpolar end-- allows polar and nonpolar substances to mix

detergent lecithin eggse.g., soap

Soap Making

A 20-mule team hauling borax out of the valley. Photo provided by the National Park Service.

Borax (Na2B4O7 _10H2O), the most widespread borate mineral was found to

help remove dirt from people and cloth. Borax is crumbly and powdery, and dissolves easily in water. Borax became an alternative to the very harsh soap

which was used prior to the discovery of borax in the late 1800's. This light and easy to use substance was hailed the world over as a washing, cleansing,

antiseptic, preservative, and medicine miracle. In the 1880s, large borate deposits were discovered in Death Valley,

California. However, the Death Valley borate deposits were located almost 170 miles from the nearest railway. In order to get the borate to the railway

economically, the owners of the Death Valley mines used large wagons pulled by teams of 20 mules. The detergents made from this borate were thus sold

as "20 Mule Team Borax".                                                                                          

A 20 mule team hauling borax in Death Valley

http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm

Soap Article

KeysKeysKeysKeys

Soap Article

ChemMatters Feb. 1985 Questions

The Story on Suds(8 min 19 sec)

Soap Article

ChemMatters Feb. 1985 Questions

Saponification

Glyceryl tripalmitate(tripalmitin)

Glycerol3 sodium palmitate(soap)

A Phospholipid

Timberlake, Chemistry 7th Edition, page 576

Stearic Acid

Kelter, Carr, Scott, Chemistry A Wolrd of Choices 1999, page 257

Fatty acidCarboxylic acid group

SoapCOO- bonds to a metal ion (Na+)

Na+

H+ lost from COOH

Cleaning Action of Soap

Micelle

Timberlake, Chemistry 7th Edition, page 573

SOAP vs. DETERGENT-- made from animal and -- made from petroleum vegetable fats -- works better in hard

water

Hard water contains minerals w/ions like Ca2+, Mg2+, and Fe3+ that

replace Na1+ at polar end of soap molecule. Soap is changed into

an insoluble precipitate (i.e., soap scum).

micelle: a liquid droplet covered w/soap or detergent molecules

Solvation

NONPOLAR

NONPOLAR

POLAR

POLAR

““Like Dissolves Like”Like Dissolves Like”““Like Dissolves Like”Like Dissolves Like”

Solvation

• Soap / DetergentSoap / Detergent– polar “head” with long nonpolar “tail”– dissolves nonpolar grease in polar water

micelle

http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm

Lab - Soap Making

KeysKeysKeysKeys

Lab:  SOAP making 

Lab:  SOAP making 

A Model of a Cell Membrane

Timberlake, Chemistry 7th Edition, page 587

Polar

Nonpolar

Cholesterol ProteinsPhospholipidbilayer

Formation of a Triglyceride

Lava LampIt is…

a philosophy

once ruled our world

an art form

progressive

post-modern

here to stay

Lava LampIt is…

a philosophy

the primordial ooze

once ruled our world

the momentan art forma classic

progressiveprehistoric

post-modern

here to stay

Polar mixtureWater

Polyethylene glycol

Nonolar mixtureChlorinated paraffin

Paraffin from kerosene

Heat transfer coil

Bulb gives heat and light

H H H H H H H H H H H H H H H H H H H H

H-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-H

H H H H H H H H H H H H H H H H H H H H

Cl H H H H Cl H H H H H Cl H H H H Cl H H H

H-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-H

H H H Cl H H H H Cl H H H H H Cl H H H Cl H

H H H H H H H H

H-O-C-C-O-C-C-O-C-C-O-C-C-O-H

H H H H H H H H

H H

O