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!!!

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.

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

Mr. M. GonzalezMr. M. Gonzalez

20082008

ObjectivesObjectives

►Compare the difference between mixtures and Compare the difference between mixtures and solutions.solutions.

►Describe how pH determines how acidic and Describe how pH determines how acidic and basic a solution is. basic a solution is.

►Determine the importance of pH in the natural Determine the importance of pH in the natural world.world.

►Narrate what pH means to you and how it affects Narrate what pH means to you and how it affects the world.the world.

• A mixture is a combination of substances in which the individual components retain their own properties and don’t react chemically.

Mixtures and SolutionsMixtures and Solutions

• Neither component of the mixture changes.

• An example of a mixture is concrete which contains cement, rock, and sand mixed

with it. Another example of a mixture is when you place oil and water in a pot- they don’t mix.

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

chemically.

Mixtures and SolutionsMixtures and Solutions

• Sugar molecules (solute) in a

powdered drink mix dissolve

easily in water (solvent) to form

a solution.

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.

• 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

• 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

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+

• 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)

►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)

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.

► The rate of certain reactions is affected by the pH The rate of certain reactions is affected by the pH of the solution. If the reaction involves a proton, of the solution. If the reaction involves a proton, or H+, then a more acidic solution will have a or H+, then a more acidic solution will have a faster rate. pH is really just a measure of the H+ faster rate. pH is really just a measure of the H+ concentration. So if H+ is a reactant, than a low concentration. So if H+ is a reactant, than a low pH will have a higher concentration of that pH will have a higher concentration of that reactant, making for a faster reaction. Similarly, reactant, making for a faster reaction. Similarly, if OH- is a reactant, than a high pH will make the if OH- is a reactant, than a high pH will make the reaction go faster because at a high pH, the reaction go faster because at a high pH, the concentration of OH- is large (and the concentration of OH- is large (and the concentration of H+ is small -- they are inversely concentration of H+ is small -- they are inversely proportional).proportional).

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

► Acids and bases can also cause Acids and bases can also cause many substances to fall apart many substances to fall apart because they can force the because they can force the bonds to break by taking away bonds to break by taking away Hydrogens and Hydroxides Hydrogens and Hydroxides from them to make water. from them to make water.

► 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

► Excess Carbon Dioxide Excess Carbon Dioxide production as a result of production as a result of burning fossil fuels increases burning fossil fuels increases the amount of acid rain in the the amount of acid rain in the atmosphere. When this rain atmosphere. When this rain comes down it kills trees and comes down it kills trees and fish by changing the pH values fish by changing the pH values of their habitat. This affects of their habitat. This affects humans indirectly by limiting humans indirectly by limiting the amount of oxygen that can the amount of oxygen that can be recycled back into the be recycled back into the atmosphere and in our atmosphere and in our dependency on fish as food or dependency on fish as food or fish meal.fish meal.

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

pH FactspH Facts

ItemItem 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

Bottled/Distilled waterBottled/Distilled water ~ 4.5~ 4.5

Question 3Question 3How can pH affect you? Write your answer in How can pH affect you? Write your answer in your note book in complete sentences. Explain your note book in complete sentences. Explain your answers.your answers.

H.W.H.W.

►Answer Hallman, “Multiple Choice,” p. 116-Answer Hallman, “Multiple Choice,” p. 116-117, #s 1-20.117, #s 1-20.

►Write out all the questions.Write out all the questions.

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?qid=20080609132156AAHSCxH