what is ph?. ph is the measurement used to determine whether a substance is acidic or basic…...
TRANSCRIPT
What is pH?
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 neither acids nor bases are neutral.
When have you seen pH measurements being used?
AcidsOften taste sour
Strong acids can burn skin & eyes
Strong acids can dissolve metals
Examples:Lemon juiceVinegarCar 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:MilkBaking sodaSoapDrain cleaner (dangerous!)
What substance is neutral?
WATER!
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
pH scale
0
pH scale
pH scale ranges from 0 -14
pH 7 is neutral; neither acid nor basePure water is pH 7
Low pH (0-6.9) = acid
High pH (7.1-14) = base
The closer to the ends of the scale, the stronger the solution is
Importance of pH
How is pH measured?
How much H+ versus OH- is present within a solutionH+ (hydrogen ion)OH- (hydroxide ion)
Ions form because of dissociation
How is pH measured?
Understanding pH measurements
Each pH unit is Each pH unit is 1010 timestimes as large as as large as the previous onethe previous one
A change of 2 pH units means A change of 2 pH units means 100 100 timestimes more basic or acidic more basic or acidic
x10x10 x100x100
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 indicatorHydrangeas (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