IntroductiontopHof

AcidsandBases

Tahoma Jr. High8th Grade ScienceMaple Valley, WA

pH(power of Hydrogen)

pH is a measurement of the numbers of H+ ions in a solution (they are very reactive without their e-), and

that’s why acids break things down.

The scale runs from 0 (or 1) through 14.

Water is made up of equal numbers of H+ and OH- ions and has a pH of 7 – or “neutral”.

(right in the middle of the scale)

0 (or 1) 7 14

strong acidNEUTRAL

strong base

Indicators are used to tell us what the pH of a substance is

weak acid weak base

pH test strips(AKA “Litmus Paper”)

are chemically treated papers that change

different colors depending on the pH of the material placed on

the paper

(you compare to the color on the box)

this would be a pH of 12 (some papers’ chemicals don’t produce green for neutral – you have to use their color scheme on the box – so don’t get your papers mixed up with other boxes!)

Another common way to test pH (especially with pools or hot tubs) is with liquid chemicals instead of treated paper.

(you compare to the color scale on the tubes)

an acid is a substance which releases

hydrogen ions when combined with water

HCl

(hydrochloric acid)

H

positive hydrogen ion

negative chlorine ion

Cl

+-

the strength of an acid depends on

how many hydrogen ions are

dissolved in the water

weaker acid stronger acid

H+

H+

H+

H+

H+

H+

H+

H+H+

H+H+

H+

HOW MANY TIMES STRONGER IS THE STRONG ACID ?

the stronger acid is three times stronger than the weak acid because there are 3x as many

hydrogen ions “to do the work”

weaker acid stronger acid

H+

H+

H+

H+

H+

H+

H+

H+H+

H+H+

H+

a base is a substance which releases

hydroxide ions when combined with water

NaOH

(sodium hydroxide)

Na

positive sodium ion

negative hydroxideion

OH

+ -

Which base below is the strongest ?

OH-OH-OH-OH-

OH-OH-

OH-

OH-OH-

A B

How much stronger ?

Base A has twice as many OH- ionsso it is twice as strong (2x)

When equal amounts of acid ions are combined with an equal number of base ions, neutralization occurs.

OH-OH-

OH-H+

H+H+

H2O

What will an ion of acid and an ion of basemake when combined ?

The other ions from the acid and the base combine to create a salt.

Na+OH-

OH-H+

Cl-H+

H2O

NaCl (table salt)

Cl-

Na+

What chemical besides water is made whenHCl and NaOH are combined ?

Neutralization

Neutralization is when one H+ ion (acid) and one OH- ion (base) are combined.

Complete neutralization occurs when there are the same number of H+ ions and OH- ions in

a solution.

This makes it neither an acid or a base. It would then have a pH of 7 (distilled/pure water).

pH of common drinks(think what these are doing to your teeth enamel…)

end show

drink pHGatorade 2.4vinegar 2.5colas 2.7

apple cider 3.17-Up 3.2

apple juice 3.4root beer 4.0

Juicy Juice 4.5coffee 5.5milk 6.5

soy milk 7.0water 7.0tea 7.2

do you want to see what happens to teeth from too much soda – any soda, not just diet soda? (or meth?) – just click again

Probably not a good idea to be “swishing” that soda around your mouth, eh?There’s phosphoric acid, carbolic acid (from the CO2), citric acid…

Colas are by far the WORST soda/juice .(we teach you this chemistry to help you protect your body/health)Teeth health is closely connected to the health of other body parts.

meth user diet soda