Download What is pH?

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What are Acids and
Bases?
Acids and Bases

Some of our favorite
foods make our
tongue curl up
because they are
SOUR.
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Bitter!

Some foods have a
“bite” of their own
because they’re
somewhat bitter.
 WHY?
Acidic/Basic
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There is a scientific reason for this:
 These foods are either acidic or basic.
 Other substances besides foods have
these characteristics.

Acids and Bases
Chemicals may be classed as acids or
bases.
 Things that are neither acids nor bases
are neutral.
 pH measures how acidic or basic a
solution is.

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On page of your Interactive
Notebook
Title the page “Acids and Bases”
 You will be taking notes on acids and
bases.

Acids
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Often taste sour *
 Strong acids can burn skin & eyes
 Strong acids can dissolve metals
 Turns blue litmus paper to red

*Never test an unknown acid by tasting it!
Bases
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Can taste bitter, sweetish, or salty *
 Often feel slippery or “soapy” *
 Strong bases can burn skin & eyes
 Turns red litmus paper to blue
 Bases react more easily with protein
than with metal; they are often used
for cleaning

*Never test an unknown base by touching or tasting it!
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No I am Not:

Some
substances
are not really
an acid or a
base: For
example,
pure water
Most Substances:
 Can
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0
be
identified as
either acidic or
basic
 Like the soil in
our backyard.
We use indicators to identify
acids and bases.

An indicator is a substance
that changes color in the
presence of an acid or a
base.
pH
The pH of a solution tells us how strong an
acid or a base the solution is.
 The lower the pH, the stronger the acid..
The higher the pH, the stronger the base.

pH Scale
0--------------7---------------14
Acid
Neutral
Base
pH < 7 are acids
pH > 7 are bases
pH = 7 is neutral
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Therefore…
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If the number is less than 7 the solution or
water is acidic
 If the number is more than 7 the solution
or water is basic

The pH Scale
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pH scale ranges from 0 -14
 pH 7 is neutral; neither acid nor base
 Pure water is pH 7
 Low pH = acid
 High pH = base
 The closer to the ends of the scale, the
stronger the solution is

Why is pH important?
Fish can’t live if the
pH is too high or too
low
Soil has to be in a
certain pH range for
plants to grow and
stay healthy.
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