 A mixture is a material composed of 2 or more elements or compounds that are physically mixed together but not chemically  Example: salt & pepper

 Heterogenous mixtures- components (parts) of the mixture are separate and distinct  Example: parts of a salad  Homegenous mixtures- has a uniform composition throughout  Also called solutions.

HETERO (DIFFERENT)HOMO (SAME)

 Solutions - mixture of 2 or more substances in which the molecules of the substance are evenly distributed (chemically combine).  Solute is the substance that is dissolved (e.g., sugar)  Solvent is the substance in which the solute dissolves (what does the dissolving), (e.g., water)  Water is the greatest solvent on Earth.

 Suspensions - are material that do not dissolve in water  Example: sand & water, Italian dressing (oil floats to the top)

 Acids release hydrogen ions (H + ) when dissolved in water.  The more H + a substance releases, the more acidic the solution becomes.  Many of the foods and beverages we eat and drink are acidic.  The substances in the stomach that break down the food are highly acidic.

 Bases release hydroxide ions (OH - ) when dissolved in water.  The more OH - a substance releases, the more basic the solution becomes.

 pH scale indicates the concentration of H + ions in a solution.  The more H + in a solution, the lower the pH is, and the more acidic it is.

 pH below 7 are acidic, they have more H + ions than they have OH -  pH above 7 are basic, they have more OH - ions than they have H +  A pH of 7 is neutral, they have the same amount of H + & OH - ions; water is neutral

 Buffers are weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes of pH.  Example: your mouth before you vomit.