2. Organic chemistry is the study of substances that contain carbon and are or once were alive. Inorganic deals with compounds that don't contain a carbon and have never been alive.
3. Matter is any substance that occupies space and has mass (weight).
4. The differences between solids, liquids, and gases deals with the size and shape. Solids have a definite size and shape; liquids have a definite size but not shape; and gases don't have a definite size or shape.
5. An element is the simplest form of matter; cannot be broken down into a simpler substance without loss of identity.
6. Atoms are the smallest particles of an element that still remain the properties of that element.
7. A molecule is a chemical combination of two or more atoms.
8. A compound is a chemical combination, whereas a mixture is a physical one.
9. Physical properties are those characteristics that can be determined without a chemical reaction and that do not cause a chemical change in the identity of the substance. Ie: color, odor, melting point, etc. Chemical properties are determined only with a chemical reaction that caused a chemical change in the identity of the substance.
10. Matter can be changed physically or chemically.
Physical change is a change in the form or physical properties without forming a new substance. An example is when solid ice melts into liquid water.
Chemical change is a change in the chemical composition of a substance, in which a new substance or substances are formed. An example is iron into rust.
11. Hydrogen is a colorless, odorless, tasteless gas and is the lightest element known. Elemental hydrogen is flammable and explosive when mixed with air.
Oxygen is the most abundant element found on earth. It is a colorless, odorless, tasteless gas.
Nitrogen is a colorless, gaseous element. It makes up about 4/5 of the air in our atmosphere and is found chiefly in the form of ammonia and nitrates.
12. Water is important for skincare because it replenishes moisture on the surface of the skin, helps keep other ingredients in solution, and helps spread products across the skin.
13. pH (potential hydrogen) is a substance's relative degree of acidity or alkalinity and is measured on a scale of 0 to 14. It is important to know the pH of the product you are working with because extreme variations in pH can damage the skin's barrier function and cause irritation or burns.
14. Oxidation is a chemical reaction that combines a substance with oxygen to produce and oxide.
Reduction is the loss of oxygen from a substance.
15. Solutions are uniform mixtures of two or more mutually mix able substances. They contain particles not visible to the naked eye and are usually transparent.
Suspensions contain particles visible to the naked eye and are not usually transparent. They usually separate over time.
Emulsions are suspensions of an unstable mixture of two or more immiscible substances united with the aid of an emulsifier. Although they may separate over time, properly formulated and stored emulsions should last at least 3 years.
16. Oil-in-water emulsions have droplets of oil surrounded by surfactants with their tails pointing in and heads pointing out.
Water-in-oil emulsions have droplets of water surrounded by surfactants with their heads pointing in and their tails pointing out.