5.1 - Acids & bases Science 10

1. Differentiate between acids, bases and salts with respect to

chemical formula, name, and properties.

2. Identify acids and bases using indicators (e.g., methyl orange,

bromthymol blue, litmus, phenolphthalein, indigo carmine).

3. Explain the significance of the pH scale, with reference to

common substances.

4. Recognize the names and formulas of common acids (ie:

Hydrochloric acid, suphuric acid, nitric acid, acetic acid).

5.1 Learning Outcomes

1. Acidic

2. Acids

3. Bases

4. Basic

5. Bromothymol blue

6. Concentration

7. Indigo carmine

8. Litmus

10. Methyl orange

11. Methyl red

12. Neutral

13. Neutralization

14. pH indicator

15. pH scale

16. Phenolphthalein

17. Salts

5.1 Vocabulary

The Scorpion is most notable for "The sting in the tale" the venom is

stored in a bulb like sack almost at the end of the tail and it is

administered to the unlucky victim through a very sharp needle point

sting. The venom paralyses its quarry in a second or less, then the

Scorpion squirts acid from its mouth onto it to dissolve the tissues

before sucking up the slushy remains.

Only 20 species of Scorpion can hurt or kill a

human with a sting. The most dealdy of all is

the 'Death Stalker‘. It is found in the deserts of

Iraq, Iran, and other neighbouring countries.

It takes up to 12 hours to die after a sting. First

you sweat, then you get dizzy and get severe

pain in your joints. Next the fever starts, and

that leads to convulsions, muscle spasms and

finally coma and death.

Interesting facts!

Bee stings are acidic with a pH of 3.5.

Along with the acid, the venom that is released by a wasp or hornet also

contains a pheromone which alarms all other wasps in the area and invites

them to join the attack on the victim. It is meant to be a signal to all wasps to

come and help. OUCH!!

Fire Ants are very aggressive and will attack anything that disturbs their mound.

After firmly grasping the skin with its jaws, the fire ant arches its back as it

inserts its rear-end stinger into the flesh, injecting venom from the poison sac. It

then pivots at the head and typically inflicts an average of seven to eight stings

in a circular pattern. Fire ant venom has a very high concentation of toxins,

which are responsible for the burning pain characteristic of fire ant stings.

Interesting facts!

Interesting facts!

Acids and Bases

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• Many familiar compounds are acids or bases.

• Lemon juice, soap, oranges, pop…

• Acids and bases can be very dangerous.

• Both can be very corrosive.

• NEVER try to identify an acid or base by taste or touch!

See pages 220 - 222

• 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

See pages 220 - 222

Acids release __________ into a solution.

Bases release _________ into a solution.

[ H+]

[OH-]

pH is the concentration of ____ expressed as a logarithm.

Every change in the pH scale of one unit is a change in

______ times the concentration of H+. Example:

• pH 4 is 10X more acidic than pH 5.

• pH 3 is 1000X more acidic than pH 5.

[ H+]

10

PH Scale

Litmus Paper Test - Website

Litmus paper, pH paper & Neutralization animations

pH of 0 to 6.9

Contribute H+ ions into

a solution

Turn litmus paper RED

Conduct ELECTRICITY

Produce H+ gas (when

added to some metals)

Are CORROSIVE

Acids!

Lemon Batteries!

• 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).

•HCl(aq) = hydrochloric acid, HNO3(aq) = nitric acid

•Acids with a carbon usually have the C written first. • CH3COOH(aq) = acetic acid

See pages 225 - 226

Acids!

• Naming acids: If you know a compound’s chemical formula, you may be able to identify whether it as an acid.

• 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.

Acids!

pH of 7.1 to 14

Donate [OH]- ions into a

solution

The hydroxide [OH-]

group is neutralized by a

hydrogen ion and water

is formed.

Turns litmus paper BLUE

Conduct ELECTRICITY

Are Slippery

Are CAUSTIC

Bases

• Bases often behave like bases only when dissolved in water.

• Therefore, bases often are written with symbol (aq) = aqueous = water.

• If you know a compound’s chemical formula, you may be able to identify it as a base.

• The chemical formula of a base usually ends with hydroxide (OH).

Bases

• 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

Bases

The pH of almost all living systems is between pH

________. Maintaining the proper pH then is vital living

systems.

pH is very important to the environment as well:

• acid rain

• agriculture

6 - 8

Why is it important to maintain pH?

Hydrangea in acidic soil Hydrangea in basic soil

Why is it important to maintain pH?

pH Indicators

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• 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 paper is the most common indicator. • There are 2 colours of litmus paper:

• Blue = basic (pH above 7)

• Red = acidic (pH below 7)

Litmus paper

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

• 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, blueberries, cabbage, pansy flower petals... are also indicators.

See pages 223 - 224

pH Indicators

pH Indicators

pH Indicators

pH Indicators

pH Indicators

Cabbage Juice paper in

baking soda (BASE)

Cabbage Juice paper in

lemon juice (ACID)

pH Indicators

pH Indicators

pH Indicators

• 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 HYDROGEN ions it has. • Square brackets are used to signify concentration, [H+], [OH–]

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

See page 228

Production of ions

• A solution cannot have BOTH high [H+] and [OH–]; they cancel each other out and form water.

• This process is called neutralization.

• H+ + OH– H2O OR H+ + OH– HOH

See page 228

NEUTRALIZATION: http://www.youtube.com/watch?v=_P5hGzA6Vb0&feature=related

Production of ions

In water, the concentration of H+ is equal to the

concentration of OH-.

By definition, pure water is ______________________

A solution is ACIDIC if the _______________

A solution is BASIC if the ________________

[ H+] = [OH-] NEUTRAL

[ H+] > [OH-]

[ H+] < [OH-]

Neutralization Reactions

Neutralization Animation

Litmus Paper, pH paper & Neutralization animations

See page 229