Review of chemistry
 An element is A pure chemical substance
consisting of one type of atom
The smallest component of an
 An atom is element having the same chemical
properties of that element
 An ion is A charged atom or molecule
 A compound is A substance containing two or
more different elements
 A molecule is A substance composed of two or
more atoms
Review of chemistry
An ionic bond is
A bond between ions in which
electrons are transferred
A covalent bond is
A bond between elements in
which electrons are shared
A hydrogen bond is
A weak covalent bond
formed between molecules
The chemistry of water
 Structure
 Chemical formula= H 0
2
 # of H atoms= 2
 # of O atoms= 1
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Partial -
The unequal distribution
of partial + and partial –
ends of a water
molecule make it polar
Partial +
Partial +
The chemistry of water
Water molecules are held
together by hydrogen bonds.
Chemistry of water
1.
2.
3.
What kinds of bonds hold the hydrogen and oxygen
together in one water molecule? Covalent bonds
What kind of bond holds the water molecules
together? Hydrogen bonds
Are the hydrogen atoms bonded together?
No, hydrogen bonds with oxygen
4.
Why is water considered a polar molecule?
It has an unequal distribution of partially + and
partially - ends
The Chemistry of Water
Why is the oxygen end of a water molecule
partially negative?
The electrons hang around
the oxygen most of the time
Why is the hydrogen
The electrons hang around the
end of a water
oxygen most of the time leaving
molecule partially the positive proton
positive?
The density of electrons in higher around the
oxygen atom versus the hydrogen atoms
Around the oxygen atom
A list of some Properties of Water
a.
High polarity and surface tension
Water’s polarity causes it to have high surface tension
b.
Cohesion and Adhesion
Attraction to itself
c.
Attraction to others
Allows H2O to rise
against gravity in
tubes and veins
Hydrogen bonds
Attaches H2O molecules together by bonding + and - together
d.
Universal solvent
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Water dissolves many polar substances
e.
Dissolves salts, acids,
sugars, alkalis and gases
High specific heat and heat of vaporization
They determine the amount of energy needed to raise the
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temp. of water and to reach its boiling point
Both allow H2O to withstand large temperature changes