Acids and Bases

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

GOALS

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!

Recall…

A molecule of water (H2O) can break apart as well

H2O H+ and OH-

Number of positive ions = number of negative ions

So water is Neutral

Water

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 H2O is neutral!

What if H+ and OH- weren’t equal?!

The pH Scale

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

Acids

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

Common Acids

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

Bases

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

Common Bases

pH Scale

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

Buffer

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

Why is pH Important?

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

pH in the Body

Enzymes◦pH is extremely important to enzymes◦Enzymes control almost all chemical

reaction in your body◦They will only work at specific pH levels!

pH in the Body