Transcript Acids & Bases

Block Day
 Stack your FCAT Website Review Packet on the
back table.
 Read and complete pages 214-217 in your textbook
on Acids, Bases and pH (the “potential of
Hydrogen”).
 In your packet, read over the Acids and Bases
Notes Worksheet and answer the questions at the
bottom.
 Pick up a lab answer sheet and put your name on it
when finished. Then read over the lab instructions
Acids & Bases
They are everywhere..
In your food
In your house
EVEN IN YOU!!!!!
What is an acid?
 An acid is a solution that has an
excess of H+ ions. It comes from the
Latin word acidus that means "sharp"
or "sour".
 The more H + ions, the more acidic
the solution.
Properties of an Acid
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Picture from BBC Revision Bites
http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_b
ases_1.shtml
Tastes Sour
Conduct Electricity
Corrosive, which means
they break down certain
substances. Many acids can
corrode fabric, skin,and
paper
Some acids react strongly
with metals
Turns blue litmus paper red
Uses of Acids
 Acetic Acid = Vinegar
 Citric Acid = lemons,
limes, & oranges. It is in
many sour candies such
as lemonhead & sour
patch.
 Ascorbic acid = Vitamin
C which your body needs
to function.
 Sulfuric acid is used in
the production of
fertilizers, steel, paints,
and plastics.
 Car batteries
What is a base?
 A base is a solution that
has an excess of OHions.
 Another word for base
is alkali.
 Bases are
substances that can
accept hydrogen ions
Properties of a Base
Feel Slippery
Taste Bitter
Corrosive
Can conduct electricity.
(Think alkaline
batteries.)
 Do not react with metals.
 Turns red litmus paper
blue.
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Uses of Bases
 Bases give soaps,
ammonia, and many
other cleaning products
some of their useful
properties.
 The OH- ions interact
strongly with certain
substances, such as dirt
and grease.
 Chalk and oven cleaner
are examples of familiar
products that contain
bases.
 Your blood is a basic
solution.
pH Scale
 pH is a measure of how acidic or
basic a solution is.
• The pH scale ranges from 0 to 14.
 Acidic solutions have pH values
below 7
 A solution with a pH of 0 is very
acidic.
 A solution with a pH of 7 is neutral.
• Pure water has a pH of 7.
• Basic solutions have pH values
above 7.
pH Scale
• A change of 1 pH unit represents a tenfold
change in the acidity of the solution.
• For example, if one solution has a pH of 1 and
a second solution has a pH of 2, the first
solution is not twice as acidic as the second—
it is ten times more acidic.
Acid – Base Reactions
 A reaction between an
acid and a base is
called neutralization.
An acid-base mixture
is not as acidic or
basic as the individual
starting solutions.
Acid – Base reactions
 Each salt listed in this
table can be formed by
the reaction between an
acid and a base.
pH of Common Substances
Timberlake, Chemistry 7th Edition, page 335
Indicator
 A substance or instrument that indicates if a
substance is an acid, base or neutral.
 Look at the list of indicators in your packet.
Reactions with indicators
Indicator
Acid
color
Neutral
color
Base
color
Phenolphthalein Colorless Faint pink Dark pink
Bromthymol
blue
Yellow
Green
Blue
Litmus
Red
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Blue
pH paper
 pH paper changes
color to indicate a
specific pH value.
Acids and Bases in Solution
 HCl + H20  H3O + + Cl(more hydronium
ions, more acidic)
 NaOH in water  Na+ + OH(more hydroxide
ions, more basic)
 NaOH + HCl  NaCl + HOH
Acid + Base
yields type of salt and water
 NH3 + H20  NH4+ + OHammonia gas + water
yields ammonium and hydroxide ions
Situations in which pH is controlled
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“Heartburn”
Planting vegetables and flowers
Fish Tanks and Ponds
Blood
Swimming pools
Acid Rain
Pollution in the air (sulfur dioxide, carbon
dioxide, nitrogen dioxide) combines with
water to form various acids.
.
Rapid changes in pH can kill
fish and other organisms in
lakes and streams.
Soil pH is affected and can kill
plants and create sinkholes
What is a SALT?
 A salt is a neutral substance produced from the
reaction of an acid and a base.
 Composed of the negative ion of an acid and the
positive ion of a base.
 One of the products of a Neutralization Reaction
 Examples: KCl, MgSO4, Na3PO4
Neutralization Reaction
 A neutralization reaction is the reaction of
an acid with a base to produce salt and
water.
 Example
H2SO4 + NaOH  NaHSO4 + H2O
Digestion and pH
 Digestion-process by which foods are broken down
into simpler substances.
 Mechanical digestion-physical process in which food
is torn apart (mouth)
 Chemical digestion- chemical reactions in which large
molecules are broken down into smaller molecules.
(stomach and small intestines)
pH in the Digestive System
 Mouth-pH around 7. Saliva contains amylase, an
enzyme which begins to break carbohydrates into
sugars.
 Stomach- pH around 2. Proteins are broken down
into amino acids by the enzyme pepsin.
 Small intestine-pH around 8. Most digestion ends.
Small molecules move to bloodstream toward
cells that use them
Digestive system
mouth
esophagus
stomach
small intestine
large intestine
To Do:
Complete the lab.
When finished, read and complete Chapters 5-7
in textbook.