ACIDS and BASES

Facts For MANY years people have known that vinegar, lemon juice and many other foods taste sour. It was not until a few hundred years ago that it was discovered why these things taste sour - because they are all acids.

Acids: ~taste sour ~release hydrogen ions (H+) in water ~have a pH lower than 7 (1-6) ~the stronger the acid, the LOWER the number on the pH scale ~Ex. HCl (hydrochloric acid)

Bases ~taste bitter ~release hydroxide ions (OH-) in water ~have a pH HIGHER than 7 (8-14) ~the stronger the base, the HiGhER the number on the pH scale ~Ex. NaHCO3 (baking soda)

ACIDS BASES taste sour, are corrosive to metals, change litmus red, and become less acidic when mixed with bases release hydrogen ions (H+) in water Acids are electrolyte. Strong acids destroy fabric. Strong acids cause burn on skin. feel slippery, Taste bitter change litmus blue, and become less basic when mixed with acids release hydroxide ions (OH-) in water They conduct electricity

Neutralization- a chemical reaction that takes place when an acid combines with a base. During this, a salt and water are formed.

Chemical and Physical Changes

Chemical Change Change from one substance to another Burning paper

Physical Change Change is physical or outward appearance. Does not change chemical make-up Wrinkled paper

Chemical Reactions Types Endothermic-energy absorbed Exothermic- energy is released

Chemical Change Change from one substance to another Evidence: Burning paper Evidence: Bubbles-gas released Color change Temperature change- Precipitant New substance is made

Chemical Reactions Evidence Temperature Change Endothermic-energy absorbed-cold Exothermic- energy is released-warm

Chemical Reactions Evidence Precipitant- solid is formed when two solutions are mixed.

Reactants the elements or compounds that are put together to form a chemical change Na + Cl  NaCl reactants

Products- the end result of reactants coming together Na + Cl  NaCl

Rates of Reactions Catalyst- speeds up a chemical reaction Inhibitor- slows down a chemical reaction (takes longer)