Organic Molecules and pH

Tomorrow we are going to be doing a pH lab using an indicator made from Red Cabbage. Here is a quick video about pH. Today you are going to do an online interactive to learn more about pH. By the end of the period, you should be able to explain what pH is, how it is measured and the difference between and acid and a base. When you are done, you may work on your project which is due tomorrow or a research journal - which is due today.

Part 1
Define pH In the lab section of your notebook, write down the definition of pH and give an example of an acid, neutral and base. Use the following information to write a definition in your own words.

pH
Under the Brønsted-Lowry definition, both acids and bases are related to the concentration of hydrogen ions present. Acids increase the concentration of hydrogen ions, while bases decrease the concentration of hydrogen ions (by accepting them). The acidity or basicity of something therefore can be measured by its hydrogen ion concentration.

In 1909, the Danish biochemist Sören Sörensen invented the pH scale for measuring acidity.A solution with [H⁺] = 1 x 10^-7 moles/liter has a pH equal to 7 (a simpler way to think about pH is that it equals the exponent on the H⁺ concentration, ignoring the minus sign). The pH scale ranges from 0 to 14. Substances with a pH between 0 and less than 7 are acids (pH and [H⁺] are inversely related - lower pH means higher [H⁺]). Substances with a pH greater than 7 and up to 14 are bases (higher pH means lower [H⁺]). Right in the middle, at pH = 7, are neutral substances, for example, pure water. The relationship between [H⁺] and pH is shown in the table below alongside some common examples of acids and bases in everyday life.

	[H+]	pH	Example
Acids	1 X 100	0	HCl
	1 x 10-1	1	Stomach acid
	1 x 10-2	2	Lemon juice
	1 x 10-3	3	Vinegar
	1 x 10-4	4	Soda
	1 x 10-5	5	Rainwater
	1 x 10-6	6	Milk
Neutral	1 x 10-7	7	Pure water
Bases	1 x 10-8	8	Egg whites
	1 x 10-9	9	Baking soda
	1 x 10-10	10	Tums® antacid
	1 x 10-11	11	Ammonia
	1 x 10-12	12
	1 x 10-13	13
	1 x 10-14	14	NaOH

Part 2 Explain how the number of Hydrogen ions changes as the pH number changes. Use this site to help you pH and the power of 10

Part 3 Explain why acids and bases act differently when they are added to water. Hint - think about H ions and OH ions. Use this site to help you pH and water