Acids & Bases SciencePower 10 (p210-235)

Journal Entry #1: Acids & Bases Copy and answer the question below into your journal. What is an acid? Give two examples of an acid. 2. What is a base? Give two examples of a base seen in everyday life. 3. What is a pH scale and what is it used for? **Hint for #1/#2: think of household products or food for examples. Acid, Base, Salt Simulation: http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/acidbasepH/ph_meter.html http://www.nclark.net/AcidsBases

Acids, Bases, and Salts Scientists often refer to substances as being either acids, bases, or salts. During scientific experiments, it is important to know what type of substance you are working with, so that you have an idea of how it might react with other elements and chemicals.

Acids, Bases, and Salts Acid: Sour-tasting compound that produces hydrogen ions (H-) when it dissolves in water and has a pH of between 0-6.9. Base: Bitter-tasting, slippery-feeling compound that produces hydroxide ions (OH-) when it dissolves in water and has a pH of between 7.1-14. Salt: An ionic compound that results from the reaction between an acid and a base. pH (“potential Hydrogen”): The relative acidity (how acidic something is) or alkalinity (how basic something is) of a substance.

What is pH? The relative acidity or alkalinity of a substance. Acidity  How acidic something is Alkalinity  How basic something is pH stands for “potential Hydrogen”: The ability of molecules to attract hydrogen ions. An acidic molecule (acid) has a low ability to attract hydrogen ions  pH of 0-6 An alkaline molecule (base) has a high ability to attract hydrogen ions.  pH of 8-14

The pH Scale Common Acids pH Common Bases                                                                                                                                                                                                           Common Acids pH Common Bases Hydrochloric acid Sulphuric acid Stomach juice Lemons Vinegar Apples Oranges Grapes Sour milk White bread Fresh milk 0.1 0.3 1-3 2.3 2.9 3.1 3.5 4 4.4 5.5 6.5 Human saliva Distilled water Blood plasma Eggs Seawater Borax Milk of magnesia Ammonia water Limewater Caustic soda 6-8 7 7.4 7.8 7.9 9.2 10.5 11.6 12.4 14

Litmus Paper – Universal pH Indicator

Characteristics of Acids Identified by the presence of a hydrogen (H) atom usually at the beginning of the chemical formula HCl Low pH (below pH of 7) Turns blue litmus paper to red Sour taste Reacts with metals to produce salt & hydrogen Reacts with carbonate salts to produce carbon dioxide

Characteristics of Bases Identified by hydroxide (OH-) ions NaOH pH between 7.1-14 Turns red litmus paper blue Slippery to the touch Taste bitter

Characteristics of Salts A salt is formed when an acid and a base are mixed. This is called an Acid-Base Neutralization reaction. Salts have a neutral pH of 7 http://www.shodor.org/unchem/basic/ab/#salts

Acid, Base, or Salt? – Activity Classify each of the following substances as either an acid, a base, or a neutral substance. Lemon Juice (pH 2.3) Eggs (pH 7.8) Blood Plasma (ph 7.4) Apples (pH 3.1) Water (pH 7) Limewater (pH 12.4) Stomach juice (pH 1-3) Vinegar (pH 2.9) Acid, Base, Salt Simulation: http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/acidbasepH/ph_meter.html http://www.nclark.net/AcidsBases