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What is pH?What is pH?

Some of our favorite Some of our favorite foods make our foods make our tongue curl up tongue curl up because they are because they are SOUR. SOUR.

Acids and BasesAcids and Bases 2

Bitter!

Some foods have a Some foods have a “bite” of their own “bite” of their own because they’re because they’re somewhat bitter.somewhat bitter.

WHY?WHY?

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The scientific reason for this:The scientific reason for this:

These foods are either acidic or basic.These foods are either acidic or basic.Liquids can be acidic or basic too Liquids can be acidic or basic too

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Acids and BasesAcids and Bases

Chemicals may be classifyied as acids or Chemicals may be classifyied as acids or bases.bases.

Things that are neither acids nor bases Things that are neither acids nor bases are neutral.are neutral.

pH measures how acidic or basic a pH measures how acidic or basic a solution is.solution is.

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AcidsOften taste sour Often taste sour **Strong acids can burn skin & eyesStrong acids can burn skin & eyesStrong acids can dissolve metalsStrong acids can dissolve metalsExamples:Examples:

Stomach acid (very strong)Stomach acid (very strong)Lemon juice, tomatoes, vinegarLemon juice, tomatoes, vinegarCar battery acid Car battery acid (dangerous!)

*Never test an unknown acid by tasting it!

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Bases Can taste bitter, sweetish, or salty * Often feel slippery or “soapy” * Strong bases can burn skin & eyes Bases are often used for cleaning Examples:

Milk Baking soda, soap, bleach Borax (like what we added to make goop) Sea water (slightly) Drain cleaner (dangerous!)

*Never test an unknown base by touching or tasting it!

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No I am Not:No I am Not: Some Some

substances substances are not really are not really an acid or a an acid or a base: For base: For example, example, pure waterpure water

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pH

pH stands for pH stands for “potential Hydrogen”“potential Hydrogen”

Acids form hydrogen Acids form hydrogen ions H+ in water.ions H+ in water.

Bases form hydroxide Bases form hydroxide ions (OH)- in waterions (OH)- in water

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How Do We Measure pH?

It’s simple! We It’s simple! We measure pH by using measure pH by using special strips of paper special strips of paper called pH papercalled pH paper

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How Does It Work? The paper is treated with The paper is treated with

chemicals that change chemicals that change color to show the pH.color to show the pH.

When the paper touches When the paper touches the substance being the substance being tested, it turns a specific tested, it turns a specific color to tell if the color to tell if the substance is an acid or substance is an acid or a base.a base.

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Acid

If the pH is less than 7, it is an acidIf the pH is less than 7, it is an acid

0--------------7---------------140--------------7---------------14

Acid Neutral BaseAcid Neutral Base

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Base

If the pH is greater than 7, it is a baseIf the pH is greater than 7, it is a base

0--------------7---------------140--------------7---------------14

Acid Neutral BaseAcid Neutral Base

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Neutral

A pH of 7 is called neutral—neither acid A pH of 7 is called neutral—neither acid nor base.nor base.

0------------7------------140------------7------------14

Acid Neutral BaseAcid Neutral Base

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The pH ScalepH scale ranges from 0 (red) -14 (bluepH scale ranges from 0 (red) -14 (bluepurplepurple))pH 7 is neutral (yellowpH 7 is neutral (yellow); neither acid nor ); neither acid nor

basebasePure water is pH 7Pure water is pH 7The closer to the ends of the scale, the The closer to the ends of the scale, the

stronger the solution isstronger the solution is

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The pH Scale16

How does pH affect our How does pH affect our environment?environment?

It can affect our soilIt can affect our soil It can affect out waterIt can affect out water

From a fish tank, to a swimming pool, to our From a fish tank, to a swimming pool, to our oceans!oceans!

It has a huge affect on our oceans!!!It has a huge affect on our oceans!!!

pH and our environment:pH and our environment:

pH in our soilpH in our soil

Acidic soil (pH is low number) is usually Acidic soil (pH is low number) is usually where oak trees grow.where oak trees grow.when oak trees leaves fall to the ground, the when oak trees leaves fall to the ground, the

soil turns acidic from the leaves – and grass soil turns acidic from the leaves – and grass can’t grow there (ever notice that green grass can’t grow there (ever notice that green grass doesn’t grow under an oak tree?)doesn’t grow under an oak tree?)

Farmers/vineyards need to keep track and Farmers/vineyards need to keep track and check the pH of their soil.check the pH of their soil.

Green grass needs a more neutral pH soilGreen grass needs a more neutral pH soil

pH in our waterpH in our water

Hot tubs and swimming pools need to have their Hot tubs and swimming pools need to have their pH levels checkedpH levels checked

Fish need a specific pH. Goldfish can’t live if Fish need a specific pH. Goldfish can’t live if there is too much ammonia ( too “basic”)there is too much ammonia ( too “basic”)

Ocean life is sensitive; ocean life can’t live in an Ocean life is sensitive; ocean life can’t live in an environment that has: environment that has: too high of pH, greater than 7 (too basic) or too high of pH, greater than 7 (too basic) or too low of a pH, less than 7 (acidic)too low of a pH, less than 7 (acidic)

But what about our water on Earth?But what about our water on Earth?

The acidity of Earth’s water is The acidity of Earth’s water is changing due to pollution: too much changing due to pollution: too much pollution creates acid rain and it is pollution creates acid rain and it is changing the acidity of our oceanschanging the acidity of our oceans..

Acid RainAcid Rain

Occurs all over the world – see mapOccurs all over the world – see map Happens because the pollution is absorbed by Happens because the pollution is absorbed by

the clouds, the clouds absorb the carbon from the clouds, the clouds absorb the carbon from the pollution, which chemically creates an acid the pollution, which chemically creates an acid - and neutral rain changes into acidic rain. - and neutral rain changes into acidic rain. Acidic rain changes the water cycle of many Acidic rain changes the water cycle of many countries countries

Over time, acid rain can destroy the metal on Over time, acid rain can destroy the metal on cars, buildings, and it can runoff into streams, cars, buildings, and it can runoff into streams, change the soil, and kill forestschange the soil, and kill forests

pH in our oceanspH in our oceans

We have too much pollution in our We have too much pollution in our atmosphere. atmosphere.

Our oceans absorb the carbon from the Our oceans absorb the carbon from the pollution, which chemically creates acid, pollution, which chemically creates acid, and then this changes the acidity of our and then this changes the acidity of our oceans. oceans.

The acidic ocean then dissolves the coral The acidic ocean then dissolves the coral reefs which are home to many varieties of reefs which are home to many varieties of sea life. Once their gone, their gone. sea life. Once their gone, their gone.

What can be done?What can be done?

We need to pay attention to our We need to pay attention to our environment. environment.

Go green – recycle, change the way you Go green – recycle, change the way you buy things, change the way you travel, buy things, change the way you travel, change the way you throw away garbage change the way you throw away garbage – a little goes a long way. – a little goes a long way.