Compounds are classified in different waysChapter 5

SCIENCE 10

Chapter 5Page 218-253

1234

5.1 Acids and BasesNotes, CYU (odds), RCs, WBook

Labs 5.1A and 5.1BTo be completed in class only

5.1 QuizIn class

5.2 SaltsNotes, CYU (odds), RCs, WBook

5678

Lab 5.2 C and 5.2 QuizTo be completed in class only

5.3 Organic CompoundsNotes, CYU (odds), RCs, WBook

Lab 5.3A and 5.3CTo be completed in class only

Chapter Test

• 20 minutes PowerPoint Lecture• 15 Minutes Workbook• 10 minutes Demo• Remainder - Lab Time (6 labs)

Class routineGet organized!!

• Assignment (all 1 package):• Make Notes for each chapter using

the headings found throughout the chapter as your section titles

• Reading Checks:• Page 225,227,228,238,247

• Check Your Understanding• Page 233, 243, 251 (odd #s)

• Understanding Key Ideas• Page 253 #16-23

At Home – Handed in on test dayGet prepared!!

ACIDSStomach acidLemonsGrapesTomatoesVitamin CAcid Rain

EggsBaking SodaSoapBleachOven cleanerLime *not the fruit!

BASES

Acids and BasesYou are familiar with them!

5.1 Acids and Bases

General formulas• Acids usually start with H

(hydrogen) on the left of the formula. Ex. HCl

• Bases usually have OH (hydroxide) on the right. Ex. NaOH

• Water is neutral• H2O has 1 H and 1 OH !!!

General properties

Acids have a pH below 7.

Bases have a pH above 7.

Water is neutral at pH 7.

pH scale

One unit of change represents a 10x (times) change in degree of acidity or basicity

• pH4 is 100x (2 steps=10 x 10) more acidic than pH6

• pH12 is 1,000,000x (6steps) more basic than pH6

• A small change in pH is a huge change in acidity or basicity

Measures how acidic or basic a solution is

pH indicators will change

colour in the presence of

acid and bases.

pH actually means

proportion or power of

Hydrogen H+ or the

concentration of H+ ions

A theoretical pOH scale

would be the opposite of pH.

Acids – pH below 7Acids release H+ ions when dissolved in Water• (aq) refers to Aqueous or “dissolved

in H2O”

Can be named by chemical name:HCl is Hydrogen Chloride

Can be named differently if shown with (aq)• Ends in “-ic acid”• HCl (aq) is Hydrochloric Acid

Sour, tangy – strong acids are corrosive

Acids that contain oxygen

Names that begin with Hydrogen and end with –ate

• H2CO3 – H2CO3 (aq)• Hydrogen carbonate – Carbonic acid

Names that begin with Hydrogen and end with -ite

• H2SO3 – H2SO3 (aq)• Hydrogen sulfite – Sulfurous acid

-ic vs. -ous

Bases – pH above 7

Bases release OH‾ (hydroxide) ions when dissolved in H2O• A basic solution is also said to be

Alkaline• Chemical name ends with hydroxide

• NaOH – sodium hydroxide• Common names vary

• NaOH

Bitter-tasting, slippery feel – strong reactive bases are caustic

If the concentration of H+ is balanced with the concentration of OH‾ the solution is neutral

• Acid has more H+• Base has more OH-

Acids and Bases: chemical oppositesWhen an acid is mixed with a base, the solutions can neutralize each other.

Some common indicators include:• Litmus paper (BAR = Blue

+ Acid turns red)• Phenolphthalein• Bromothymol blue• Indigo carmine• Methyl orange, • Methyl red

pH indicatorsAn indicator changes colour depending on the pH.

Modified Lab:1. Create a pH

number scale (#6)2. Create an

indicator chart for Red Cabbage indicator.

3. Tape the indicator paper to the chart for 6+ samples4. I notice, I Wonder x3each5. Name Date & Hand in

Some household items are indicatorsRed Cabbage – Lab 5.1A (page 221)

Red Cabbage Indicator

The cabbage is actually PURPLE.

• Turns GREEN in something basic• Turns RED in something acidic

• Estimate the intensity of the change for your chart… more intense red is more acidic…

Pigment responsible: anthocyanin

Lab 5.1B Page 230

1. Question2. Data Table3. Analyze questions *full sentence

response4. Conclude and apply *full sentence

response5. Name Date

Handing in the following on a sheet of paper

Lab 5.2C Page 241

1. Question2. Data Table3. Analyze *full sentence responses4. Conclude and Apply *full sentence

responses5. Name Date

Handing in the following on a sheet of paper

(c) McGraw Hill Ryerson 2007

5.1 Acids and Bases

• Many familiar compounds are acids or bases. Classification as acids or bases is based on chemical composition.

• Acids and bases can be very dangerous. Both can be very corrosive.

NEVER try to identify an acid or base by taste or touch!• The strength of acids and bases in measured on the pH scale.

pH below 7 = acidic, pH above 7 = basic, pH 7 = neutral 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Acids Neutral Bases Each decrease of 1 on the pH scale indicates 10× more acidic

For example, pH 4 is 10 times more acidic than pH 5. pH 3 is 1000 times more acidic than pH 6.

See pages 220 - 222

(c) McGraw Hill Ryerson 2007

pH Indicators

• The pH of acids and bases cannot be determined by sight. Instead, pH is measured by other chemicals called indicators

or by a pH meter that measures the electrical conductivity of the solution.• pH indicators change colour based on the solution they are placed in.

Litmus is the most common indicator, and is used on litmus paper. Two colours of litmus paper: Blue = basic and Red = acidic. Blue = pH above 7, Red = pH below 7.

Universal indicator contains many indicators that turn different colours at different pH values (can be in liquid form, or on paper strips like litmus).

A pH meter uses electrical probes to measure how solutions conduct electricity. Indicators change colour at different pH values, so different indicators are used to

identify different pH values. Bromothymol blue for pH 6 – 7.6, phenolphthalein for pH 8.2 – 10. Many natural sources, such as beets and cabbage,

are also indicators.

See pages 223 - 224

Litmus paper

(c) McGraw Hill Ryerson 2007

Acids

• If you know a compound’s chemical formula, you may be able to identify whether it as an acid. Acids often behave like acids only when dissolved in water. Therefore, acids often are written with symbol (aq) = aqueous = water.

• The chemical formula of an acid usually starts with hydrogen (H). Acids with a carbon usually have the C written first.

HCl(aq) = hydrochloric acid, HNO3(aq) = nitric acid, CH3COOH(aq) = acetic acid• Naming acids

Hydrogen + …-ide = hydro…ic acid HF(aq) = hydrogen fluoride = hydrofluoric acid

Hydrogen + …-ate = …ic acid H2CO3(aq) = hydrogen carbonate = carbonic acid

Hydrogen + …-ite = …ous acid H2SO3(aq) = hydrogen sulphite = sulphurous acid

See pages 225 - 226

Sulfuric acid is

used in batteries.

(c) McGraw Hill Ryerson 2007

Bases

• If you know a compound’s chemical formula, you may be able to identify it as a base. Bases often behave like bases only when dissolved in water. Therefore, bases are often written with the symbol (aq) = aqueous = water.

• The chemical formula of a base usually ends with hydroxide (OH).• Bases can be gentle or very caustic.• Examples of common bases:

NaOH(aq)

Mg(OH)2(aq)

Ca(OH)2(aq) NH4OH(aq)

See page 227

(c) McGraw Hill Ryerson 2007

Production of Ions

• Acids and bases can conduct electricity because they release ions in solution. Acids release hydrogen ions, H+ . Bases release hydroxide ions OH–.

• The pH of a solution refers to the concentration of ions it has. Square brackets are used to signify concentration, [H+], [OH–]

High [H+] = low pH, very acidic High [OH–] = high pH, very basic

A solution cannot have BOTH high [H+] and [OH–]; they cancel each other out and form water. This process is called neutraliztion.

H+ + OH– H2O

See page 228

(c) McGraw Hill Ryerson 2007

Properties of Acids and Bases

See page 229

Take the Section 5.1 Quiz