Presentation on theme: "What is pH?. pH is the measurement used to determine whether a substance is acidic or basic… Chemicals may be classed as acids or bases. Things that are."— Presentation transcript:
pH is the measurement used to determine whether a substance is acidic or basic… Chemicals may be classed as acids or bases. Things that are neither acids nor bases are neutral. When have you seen pH measurements being used?
Acids Often taste sour Strong acids can burn skin & eyes Strong acids can dissolve metals Examples: Lemon juice Vinegar Car battery acid (dangerous!)
Bases Can taste bitter, sweetish, or salty Strong bases can burn skin & eyes Bases react more easily with protein than with metal; they are often used for cleaning Examples: Milk Baking soda Soap Drain cleaner (dangerous!)
A special name is given to the acid or base characteristic that a substance has: It is called: pH “ p ” stands for potential and “ H ” stands for hydrogen; hence, the potential of a substance to attract hydrogen ions
Understanding pH measurements Each pH unit is 10 times as large as the previous one Each pH unit is 10 times as large as the previous one A change of 2 pH units means 100 times more basic or acidic A change of 2 pH units means 100 times more basic or acidic x10x100
pH indicators pH indicator is a halochromic chemical compound that is added in small amounts to a solution so pH can be determined visually. Chemical detector for H+ Color of solution changes depending on pH Litmus paper Digital pH indicators Natural indicator Hydrangeas (blue in more acidic soil; pink/red in alkaline soil)
Buffers Homework: What is a buffer? How does it relate to pH? Read this tutorial from Carnegie Mellon University http://chemcollective.org/activities/tutorials/buffers/ buffers3