What are the properties of Ionic compounds,
molecular compounds, acids, bases and salts?
 Ionic compounds are made up of ions
 Molecular compounds are made of molecules
containing atoms that are covalently bonded.
 Ionic and molecular compounds have different
properties
 Ionic compounds form hard crystals with high melting
points and conduct electric current when dissolved in
water or melted.
 Molecular compounds do not conduct electric current
when melted or dissolved in water and have lower
melting and boiling points
 Ionic compounds form solids by building up repeating
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patterns of ions. They form a 3 dimensional arrangement
called a crystal.
Many crystals of ionic compounds are hard and brittle.
Ions in an ionic compound must break apart for the
compound to melt. It takes huge amount of thermal energy
to separate the ions in a crystal.
Compared to an ionic compound, a molecular compound
needs less heat to separate the molecules because the
forces holding them together are weaker.
Molecular compounds have much lower melting and
boiling points.
 In essence:
 A typical ionic compound is a crystal, hard and brittle.
 Melting points of ionic compounds are high.
 They conduct electricity when they are dissolved in
water or melted.
 Molecular compounds do not conduct electric currents
and have lower melting points and boiling points
 Electrical conductivity(property of ionic compounds):
electric current is the flow of charged particles.
 Example: what happens to salt when it is dissolved in
water? The ions of sodium and chlorine become far
apart that their opposite charges don’t hold them in
fixed position anymore. The ions can move carrying
current. In general any food containing saltwater could
be used to conduct electric current
 Page 377 – apply it.
 Students working in groups answer questions 1,2,3
 Acids are compounds with specific characteristic properties.
 An acid reacts with metals and carbonates, tastes sour and turns
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blue litmus paper red.
A compound that changes color when it comes into contact with
an acid is called an indicator.
Many common items contain acids. Folic acid is in green
vegetables. Hydrochloric acid is in your stomach helping with
your digestion. Sulfuric acid is in batteries.
Acids react with metals to produce hydrogen gas.(examples: iron,
copper, zinc. Gold and platinum do not react).That is why acids
are described as corrosive.
Sour taste is a characteristic of acids( lemons, vinegar, grape
juice, tomatoes)
 Bases another group of compounds is the opposite of acids
 A base tastes bitter, feels slippery and turns red litmus paper blue.
 Common bases include ammonia found in household cleaners, and
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baking soda.
Unlike acids, bases don’t react with metals or carbonates.
Bitter taste: example tonic water.
Slippery feel: soaps, shampoos, and detergents that contain bases.
Indicators: bases turn red litmus paper blue.
Main difference between acids and bases is that acids release hydrogen
ions when dissolved whereas bases release hydroxide ions when
dissolve.
A common misconception is that only acids not bases can cause
physical injury. Example a drain cleaner that contains a very strong
base and that can injure the skin, eyes, nose mouth.
 Neutralization is a reaction between an acid and a
base. It produces salt and water.
 It involves a positive ion of a base and a negative ion of
an acid which cancel out or neutralize each other.
 Salts are made of ions and share the properties of ionic
compounds, i.e. crystal shape, high melting and
boiling points, and electric conductivity.
 Students work in groups on page 380 .Answer question
about how can bonding determine the properties of a
compound and water H2O.
 Acids and bases can be measured using the pH scale.
 The pH scale ranges from 0 to 14.
 Most acidic substances are found at the low end of the scale
while bases are found at the high end.
 You can find the pH of a substance using indicator paper,
which changes color for each pH value.
 A pH lower than 7 is acidic. A pH higher than 7 is basic..If
it is exactly 7 is neutral, neither acid nor base. Water and
salts are neutral.
 Students work in groups on page381 to answer section
“assess your understanding”.
 Home learning:
 Create a poster that shows examples of common acids
and bases. Create your own art. Review the properties
of acids and bases so you can make appropriate
selections.
 Use a cardboard or construction paper.