Take out a scrap piece of paper… List 2 acids and 2 bases

 By the end of today you should be able to…  Define acid, base, pH, and buffer  Describe why substances below a pH of 7 are acidic and why substances above a pH of 7 are basic  Describe 2 examples of pH in your body

 A solution is… ◦ A mixture where all the components are evenly distributed (salt water)  When substances like salt or sugar dissolve in water the break up into ions ◦ NaCl  Na + and Cl -  Sometimes we call ions electrolytes ◦ Like in Gatorade!

 A molecule of water (H 2 O) can break apart as well  H 2 O  H + and OH -  Number of positive ions = number of negative ions  So water is Neutral

 pH Scale – a measurement system used to show the amount of H + in a solution  “potential hydrogen”  0 – 14; pH of 7 has equal parts H + and OH -  That’s why H 2 O is neutral!  What if H + and OH - weren’t equal?!

 Acid – a compound that forms H + ions when in a solution  Contain more H + ions than pure water  Have a pH value below 7  The lower the pH, the stronger the acid  Taste sour or tangy

 Milk = 6.6  Tomatoes = 4.5  Vinegar = 2.5  Lemon Juice = 2.0  Battery Acid = 1.0

 Base – a compound that forms OH - ions when dissolved in a solution  Contain fewer H+ ions than pure water  pH value above 7  The higher the pH the stronger the base  Make your skin feel slippery

 Blood = 7.4  Baking Soda = 8.3  Ammonia = 11.0  Bleach = 12.6

 Buffer – a substance that helps to prevent sudden changes in pH  This is especially useful in the body where some chemical reactions only work at certain pH levels

 We use acids and bases in every day life ◦ Many household cleaners are bases ◦ Some of the foods we eat are acids ◦ Farmers must maintain the pH of the soil ◦ We monitor the pH of our swimming pools

 Digestion ◦ Stomach acid has a pH of 1-2 ◦ This is necessary to break down the foods we eat  Blood ◦ Blood has a pH around 7.4 ◦ pH plays an important role in the amount of oxygen carried by your blood

 Enzymes ◦ pH is extremely important to enzymes ◦ Enzymes control almost all chemical reaction in your body ◦ They will only work at specific pH levels!

 A change of pH of 1 is 10x the concentration of H + ions  pH of 4 has 10 times as many H + as a pH of 5!

 A pH of 6 is how many times more acidic than a pH of 8?  pH of 3 is how many times less acidic than a pH of 2?  pH of 12 is how many times less acidic than a pH of 4?