Acids and Bases. Think back to a time when you have eaten something very sour… Think back to a...

Acids and Bases

Think back to a time when you have eaten something very sour…

Think back to a time when you have eaten something very bitter…

What were your reactions to each?

SOUR!!

Bitter taste…

What causes some things to taste sour, and others to taste bitter?

It’s all about ACIDS and BASES

Its all about H+ and (OH –) ions

The pH Scale

Things you need to know about the pH scale

• The pH scale measures how acidic or basic a substance is

• The pH scale ranges from 0 -14

• 0 - 6.99 = acids• 7.0 = neutral• 7.01-14 =bases

• 0 = most acidic• 14= least acidic / MOST

BASIC

The pH Scale


• The pH scale measures the concentration of H+ ions in a solution

• A solution with a pH of 0 is very acidic, with a high H+ concentration (lots of H+ ions and not a lot of OH- ions)

• Acid- a compound that release H+ ions in a solution

The pH Scale


• A solution with a pH of 14 is very basic, with a low H+ concentration (lots of OH- ions and not a lot of H+

ions)

• Base- compounds that remove H+ ions from a solution

• A solution with a pH of 0 is neutral - neither acidic nor basic, with equal number of H+ and OH- ions

Why do acids have more H+ ions and bases have less H+ and more OH- ions?

• Acid – donates H+ when added to aqueous solutions

• Base – breaks up into hydroxide (OH-) ions when added to a aqueous solution

**An aqueous solution is a solution in which the solvent (what is doing the dissolving) is water

Where have you heard the word “buffer” in your everyday life?

• For example, “Family and friends can provide a buffer against stress.”

Definition• Buffer - a person or thing that prevents

incompatible or antagonistic people or things from coming into contact with or harming each other.

A Buffer in Science works the same way!

• Buffers- regulate the pH in an organisms– A compound that can bind to an H+ ion when the

concentration increases, and can release H+ ions when the concentration decreases

– Buffers “lock up” ions and helps the organism maintain homeostasis

BasicACIDIC

If the pH in a stomach increases from a pH of 4 to a pH of 6, how does the hydrogen ion concentration change?

-If the pH in a stomach increases from a pH of 4 to a pH of 6, how does the hydrogen ion concentration change?

-In other words, how many MORE H+ ions do you have at a pH of 4 compared to a at pH of 6?

pH Value H+ ConcentrationRelative to Pure Water Example

0 10,000,000 battery acid

1 1,000,000 concentrated sulfuric acid

2 100,000 lemon juice, vinegar

3 10,000 orange juice, soda

4 1,000 tomato juice, acid rain

5 100 black coffee, bananas

6 10 urine, milk

7 1 pure water

8 0.1 sea water, eggs

9 0.01 baking soda

10 0.001 Great Salt Lake, milk of magnesia

11 0.000 1 ammonia solution

12 0.000 01 soapy water

13 0.000 001 bleach, oven cleaner

14 0.000 000 1 liquid drain cleaner

-If the pH in a substance increases from a pH of 4 to a pH of 6, how does the hydrogen ion concentration change?

• pH of 4 = 1,000• pH of 6 = 10

• How does the hydrogen ion concentration change?


• pH of 4 = 1,000• pH of 6 = 10


ANSWER - the hydrogen concentration decreased by a factor of 100


• pH of 2 = 100,000• pH of 5 = 100



• pH of 1 = 100,000• pH of 5 = 100

ANSWER - the hydrogen concentration decreased by a factor of 1,000

-If the pH in a substance decreases from a pH of 7 to a pH of 5, how does the hydrogen ion concentration change?

• pH of 7 = 1• pH of 5 = 100


-If the pH in a substance decreases from a pH of 7 to a pH of 5, how does the hydrogen ion concentration change?

• pH of 7 = 1• pH of 5 = 100

ANSWER - the hydrogen concentration increases by a factor of 100

Practice

• pH Lab!!

Acids and Bases. Think back to a time when you have eaten something very sour… Think back to a...

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