3.3 Matter, Solutions, Suspensions, Emulsions & the pH Scale

3.3 Matter, Solutions, Suspensions, Emulsions & the pH Scale

Cosmetology is applied chemistry. Every shampoo, hair color formula, permanent wave lotion, and skin cream relies on chemical interactions. Cosmetologists must understand the classification of matter, physical and chemical changes, cosmetic liquid mixtures, and the critical importance of maintaining proper pH balance during salon services.

Basics of Matter & Chemical States

Matter is defined as any substance that occupies space and has mass (weight). All matter is composed of elements—pure chemical substances that cannot be broken down into simpler substances by ordinary chemical means. There are 118 known elements, 92 of which occur naturally.

States of Matter

1. Solid: Rigid state with a definite shape and definite volume (e.g., ice, hair shears, fingernail plates).
2. Liquid: Fluid state with a definite volume but no definite shape, taking the shape of its container (e.g., shampoo, developer, hydrogen peroxide).
3. Gas: Unconfined state with neither definite volume nor definite shape (e.g., steam, propellant gases, atmospheric air).

Atoms, Molecules, and Chemical Changes

• Atom: The smallest chemical particle of an element that retains structural identity.
• Molecule: Formed by chemically joining two or more atoms (e.g., elemental molecule O2; compound molecule H2O).

Physical vs. Chemical Changes

• Physical Change: An alteration in the form or physical properties of a substance without a chemical reaction or creation of a new substance. Example: Ice melting into water, or applying temporary hair chalk coating the cuticle.
• Chemical Change: An alteration in the chemical composition of a substance, creating new substances with distinct chemical properties. Example: Permanent hair color oxidizing with hydrogen peroxide, or permanent wave solution breaking disulfide bonds.

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Physical Mixtures: Solutions, Suspensions & Emulsions

Most cosmetic products used in the salon are physical mixtures of two or more substances combined in varying proportions.

PHYSICAL MIXTURES IN THE SALON:
├── SOLUTIONS: Stable, clear, dissolved solute in solvent (e.g., hydrogen peroxide)
├── SUSPENSIONS: Unstable, cloudy, undissolved particles settle (e.g., nail polish)
└── EMULSIONS: Immiscible liquids held by surfactant emulsifiers (O/W vs W/O creams)

Mechanics of Solutions

• Solute: The substance that is dissolved in a solution (e.g., salt or hair dye powder).
• Solvent: The liquid that dissolves the solute to form a solution (e.g., water). Water is known as the universal solvent because it dissolves more substances than any other solvent.
• Miscible Liquids: Liquids that can be mixed together in any proportion without separating (e.g., water and alcohol).
• Immiscible Liquids: Liquids that are not capable of being mixed to form stable solutions (e.g., water and oil).

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Emulsions & Surfactant Mechanics

An emulsion is an unstable physical mixture of two or more immiscible liquids held together by a binder called an emulsifier. An emulsifier acts through surfactants (surface-active agents).

Surfactant Molecule Structure

A surfactant molecule has two distinct ends:

   [ HYDROPHILIC HEAD ] ===========~=~=~=~=~= [ LIPOPHILIC TAIL ]
      (Water-Loving)                             (Oil-Loving)
   Attracts Water/Moisture                    Attracts Oil/Dirt/Sebum

1. Hydrophilic Head: Water-loving head that dissolves easily in water.
2. Lipophilic Tail: Oil-loving tail that dissolves easily in fats, oils, and grease.

During shampooing, the lipophilic tails attach to oil, dirt, and sebum on the scalp, while the hydrophilic heads attach to rinse water, lifting the debris away.

Types of Salon Emulsions

• Oil-in-Water (O/W) Emulsion: Oil droplets emulsified into a continuous water base. Easily rinsed off with water. Includes most salon shampoos, hair conditioners, skin creams, and body lotions.
• Water-in-Oil (W/O) Emulsion: Water droplets emulsified into a continuous oil base. Feels greasier and harder to rinse away. Includes cold creams, night moisturizing creams, and heavy sunscreens.

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The pH Scale & Chemical Balance

The term pH stands for potential Hydrogen, representing the quantity of hydrogen ions in a water-based solution. Only water-containing solutions have a pH value; pure oils, waxes, and alcohol powders have no pH.

ACIDIC (0 - 6.9)              NEUTRAL (7.0)          ALKALINE (7.1 - 14.0)
<==================================|==================================>
0    3    4.5    5.5    6.9        7.0       7.1    9.0    11.0    14.0
[Acid Mantle of Skin/Hair]    Pure Water    [Perm Lotion]  [Relaxer]

The Logarithmic Nature of pH

The pH scale ranges from 0 to 14. It is a logarithmic scale, meaning each whole unit change represents a 10-fold (10x) change in concentration of acidity or alkalinity:

• pH 6 is 10 times more acidic than pure water (pH 7).
• pH 5 is 100 times (10 x 10) more acidic than pure water (pH 7).
• pH 4 is 1,000 times (10 x 10 x 10) more acidic than pure water (pH 7).
• pH 9 is 100 times more alkaline than pure water (pH 7).

Natural pH of Hair, Skin & Nails

The skin and hair possess a natural protective film called the acid mantle (composed of sweat, sebum, and dead skin cells) with a natural pH of 4.5 to 5.5. Preserving this acid mantle protects against bacterial proliferation and maintains cuticle integrity.

Acidic vs. Alkaline Action on Hair Cuticle