Do now:Do now:

►What happens when you combine baking soda What happens when you combine baking soda and vinegar?and vinegar?

A Chemical Reaction!!!

What is pH?

AnswerAnswer

► The reaction between baking soda (NaHCO3) and vinegar (CH3COOH) is The reaction between baking soda (NaHCO3) and vinegar (CH3COOH) is actually two reactions, an acid base reaction followed by a decomposition actually two reactions, an acid base reaction followed by a decomposition reaction.reaction.

1) When the two ingredients are mixed, hydrogen ions ( H+) from the vinegar 1) When the two ingredients are mixed, hydrogen ions ( H+) from the vinegar react with the bicarbonate ions (HCO3- ) from the baking soda to form a new react with the bicarbonate ions (HCO3- ) from the baking soda to form a new chemical called carbonic acid (H2CO3).chemical called carbonic acid (H2CO3).

2) The carbonic acid thus formed then immediately decomposes into carbon 2) The carbonic acid thus formed then immediately decomposes into carbon dioxide gas (CO2) and water (H2O).dioxide gas (CO2) and water (H2O).

H2CO3 ---> H2O + CO2H2CO3 ---> H2O + CO2

It's this carbon dioxide gas that you see bubbling and foaming as soon as you It's this carbon dioxide gas that you see bubbling and foaming as soon as you mix baking soda and vinegar together.mix baking soda and vinegar together.

What is pH?

Baking soda

Vinegar

Carbonic Acid

Decomposition

Carbon Dioxide Dihydrogen Oxide

AcidBase

What is pH?

What is pH?

HWHW

► If you haven’t submitted your 1If you haven’t submitted your 1stst lab report draft on lab report draft on germination, please do so ASAP.germination, please do so ASAP.

Aim: What is pH?Aim: What is pH?

Mr. M. GonzalezMr. M. Gonzalez

What is pH?What is pH?

ObjectivesObjectives

►I can define what mixtures and solutions are.I can define what mixtures and solutions are.►I can describe how pH determines how acidic I can describe how pH determines how acidic

and basic a solution is. and basic a solution is. ►I can determine the importance of pH in the I can determine the importance of pH in the

natural world.natural world.

What is pH?

• A mixture - combination of substances that retain their own properties and don’t react

chemically even when mixed.

Mixtures and SolutionsMixtures and Solutions

• Neither component of the mixture changes.

• E.g. = concrete = cement, rock, and sand.

• E.g. = kool aid = water, sugar, coloring, and flavor.

What is pH?

• A solution is a mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent) and they dissolve.

Mixtures and SolutionsMixtures and Solutions

• Sugar molecules (solute) in a

powdered drink dissolve in water (solvent) to form a solution.

What is pH?

Question 1Question 1What is the difference between a mixture and a What is the difference between a mixture and a solution?solution? (NY: St 4 KI 6.1c) (NY: St 4 KI 6.1c)

In a mixture there are substances that don’t react, they are just nearby to each other while in a solution the substances can react in many different ways.

What is pH?

• Chemical reactions can occur only when conditions are right. Especially reactions that involve enzymes in living things.

What are acids and bases?What are acids and bases?

• A chemical reaction may depend on:- energy availability- temperature- concentration of a substance

- pH of the internal or surrounding environment

What is pH?

• The pH is a measure of how acidic (H+) or basic (-OH) a solution is.

Acids and basesAcids and bases

• A scale with values ranging from below 0 to above 14 is used to measure pH.

NeutralMore acidic More basic

What is pH?

Acids and basesAcids and bases

• Acids have a lot of Hydrogen ions (H+) and bases have a lot of Hydroxide ions (-OH).

• A solution is neutral if its pH equals seven.

More acidic More basicNeutral

H+

H+

H+H+

H+H+

H+

H+H+

H+

H+

H+

H+

H+H+

H+

H+

H+

H+

H+

H+

H+

-OHH+

(H+) + (-OH) =

H2OH+

-OH

-OH

-OH

-OH-OH

-OH-OH-OH

-OH

-OH-OH

-OH

-OH-OH

-OH

-OH H+

What is pH?

• Substances with a pH above 7 are basic. A base is any substance that forms hydroxide ions (-OH) in water.

Acids and basesAcids and bases

Ammonia (pH 11)

What is pH?

►Substances with a pH Substances with a pH below 7 are acidic. below 7 are acidic. An An acidacid is any is any substance that forms substance that forms hydrogen ions (hydrogen ions (HH++) in ) in water.water.

Acids and basesAcids and bases

Vinegar (pH 3)

What is pH?

Question 2Question 2What are acids and bases? Give examples.What are acids and bases? Give examples.

An acid basically has an excess of Hydrogen ions ((HH++)) and a base has an excess of Hydroxide ions (-OH) .

Examples can be: lemon juice, ammonia, vinegar, drinking water, hydrated lime, clorox, drano, seltzer water, etc.

What is pH?

► Chemical reactions rate is affected by the pHChemical reactions rate is affected by the pH..

► If the reaction involves a proton, or H+, a more If the reaction involves a proton, or H+, a more acidic solution will have faster rate. acidic solution will have faster rate.

► Similarly, if OH- is a reactant, than a high pH Similarly, if OH- is a reactant, than a high pH will make the reaction go faster because at a will make the reaction go faster because at a high pH, the concentration of OH- is large.high pH, the concentration of OH- is large.

Importance of pH in the natural worldImportance of pH in the natural world

What is pH?

► Acids and bases cause many Acids and bases cause many substances to fall apart because substances to fall apart because they break bonds by taking they break bonds by taking away away HydrogensHydrogens and and HydroxidesHydroxides from them to make from them to make waterwater. .

► Acids and bases are used in Acids and bases are used in cooking, cleaning, making cooking, cleaning, making computers, batteries, enzyme computers, batteries, enzyme reactions in your body, reactions in your body, digestion, and countless other digestion, and countless other things.things.

Importance of pH in the natural worldImportance of pH in the natural world

What is pH?

► Carbon Dioxide Carbon Dioxide from burning from burning fossil fuels fossil fuels increases the amount increases the amount of of acid rain acid rain in the atmosphere. in the atmosphere.

► Acid rain Acid rain kills trees and fish by kills trees and fish by changing the changing the pH values pH values of their of their habitat.habitat.

► Humans affected by:Humans affected by:

► limiting oxygen in limiting oxygen in atmosphere,atmosphere,

► Kills fish we depend on as Kills fish we depend on as food or fish meal.food or fish meal.

► Global warming and sea Global warming and sea rise.rise.

Importance of pH in the natural worldImportance of pH in the natural world

What is pH?

What’s the perfect pH for a plant?What’s the perfect pH for a plant?

►Living things are Living things are especially sensitive to especially sensitive to changes in pH.changes in pH.

►Plants, for example, will Plants, for example, will be incapable of be incapable of absorbing nutrients absorbing nutrients from the soil if the pH from the soil if the pH is:is:

►too low (too low (acidicacidic) or ) or

►too high (too high (basicbasic).).

Background InformationBackground Information

pH FactspH FactsItemItem pHpH

Human BloodHuman Blood 7.417.41

Ocean WaterOcean Water 8.28.2

Acid RainAcid Rain < 5.6< 5.6

MilkMilk ~ 6.4~ 6.4

BeerBeer 4 - 54 - 5

VinegarVinegar ~ 3~ 3

Human StomachHuman Stomach 1.5 - 31.5 - 3

NitrificationNitrification 77

HydroponicsHydroponics 5.8 – 6.25.8 – 6.2

Ultra-filtered/Distilled waterUltra-filtered/Distilled water ~ 4.5~ 4.5

REMEMBER: REMEMBER: The reason why acids and The reason why acids and bases are so important is bases are so important is that they can that they can speed up or speed up or

slow down chemical slow down chemical reactionsreactions..

What is pH?What is pH?

What are chemical What are chemical reactions?reactions?

What is pH?What is pH?

WHEN WHEN

CHEMICAL BONDSCHEMICAL BONDS

FORMFORM

AND/ORAND/OR

BREAK BREAK

WE CALL THESEWE CALL THESE

CHEMICAL REACTIONSCHEMICAL REACTIONS What is pH?

Compound Molecule SpiralCompound Molecule Spiral

What is pH?

Journal entryJournal entry

►What’s the importance of pH in the natural What’s the importance of pH in the natural world and you?world and you?

►Give 2 specific examples.Give 2 specific examples.

What is pH?

What is pH?

HWHW

► If you haven’t submitted your 1If you haven’t submitted your 1stst lab report draft on lab report draft on germination, please do so ASAP.germination, please do so ASAP.

BibliographyBibliography

►““Biology: The Dynamics of Life.” Biology: The Dynamics of Life.” Glencoe Glencoe Interactive ChalkboardInteractive Chalkboard. The Living Environment . The Living Environment Edition. CD-ROM. New York: McGraw Hill, Edition. CD-ROM. New York: McGraw Hill, 2003.2003.

►Yahoo Answers . 06/17.08 Yahoo Answers . 06/17.08 http://answers.yahoo.com/question/index?http://answers.yahoo.com/question/index?qid=20080609132156AAHSCxHqid=20080609132156AAHSCxH

What is pH?