A Look at Water and Its
Contaminants
Water Part B
Physical Properties of Water
• Matter
–anything that occupies space and has
mass
Physical Properties of Water
• Physical Properties: can be observed or
measured without changing the identity
of a sample of matter
• Examples:
–Boiling point, melting point, density,
color
Physical Properties of Water
• Density: mass  volume
• the density of liquid water is 1.00 g/mL
Physical Properties of Water
• Physical state affects density:
– gases are much less dense than liquids
– solid form of a substance is usually denser than its
liquid form
– EXCEPT WATER: As water freezes it occupies a
larger volume (d = 0.92 g/mL)
• the density of liquid water is 1.00 g/mL
Physical Properties of Water
• clear, odorless, colorless, and tasteless
• easily changes to each of the three phases of
matter
• “universal solvent”- so many substances easily
dissolve in water to make aqueous solutions.
Physical Properties of Water
• high boiling point 100 C
• high surface tension
Mixtures and Solutions
• Mixture: two or more substances are mixed
together and they keep their individual
properties
– Heterogeneous mixture: a mixture that is not
uniform throughout
• Example: Chocolate chip cookie
– Homogeneous mixture (Solution): a mixture that
is uniform throughout
• Example: Peanut Butter Cookie
Mixtures and Solutions
• Mixtures are classified by size of the particles
in the mixture.
Mixtures and Solutions
Solution- smallest particle size,
• salt water
• Solute- substance that is dissolved
• Solvent- substance that does the
dissolving
• Kool-Aid
Mixtures and Solutions
– Colloid-medium particle size,
• Fog
• Shows the Tyndall Effect light is scattered in
many directions and can easily be seen.
• like seeing dust particles in the light beam of a light
Mixtures and Solutions
– Suspension-largest particle size,
• medicine that says “shake before using”
Particulate View of Water
• Atoms: All matter is composed of atoms;
smallest particles possessing the properties of
an element
• Element: matter that is made up of only one
kind of atom
• oxygen is an element because it is composed
of only oxygen atoms
• 90 elements are found in nature!
Particulate View of Water
• Compound: substances composed of two or
more elements linked together chemically in
fixed proportions
• water
H2O
• table salt
NaCl
• ammonia
NH3
• baking soda NaHCO3
• chalk
CaCO3
Symbols, Formulas & Equations
• Chemical Symbols: the international language
of chemists and scientists across the planet
• each element is assigned a symbol
• the first letter is capitalized; all other letters
are lowercase
• Al, Cl, Ag, Mg
Symbols, Formulas & Equations
Subscripts: a number written below which
indicates the number of atoms of each
element that are present in a substance
H2O
2 Atoms of hydrogen
1 Atom of oxygen
C3H8
3 Atoms of carbon
8 Atoms of hydrogen
Symbols, Formulas & Equations
• Chemical reactions: creating new substances
• the new substances have completely different
properties than the original substances.
2H2 + O2  2H2O
Hydrogen + Oxygen 
Water
Reactants

Products
Symbols, Formulas & Equations
• Diatomic molecules: elements that exist as
two bonded atoms of the same element
• H2, N2, O2, F2, Cl2, Br2 & I2
• All other elements are written at single atoms
(Ca, Fe, Na & Mg)
The Electrical Nature of Matter
• Remember: LIKE CHARGES REPEL AND UNLIKE
CHARGES ATTRACT!
• Atoms have:
– Protons- positive
– Electrons- negative
– Neutrons-neutral (no charge)
The Electrical Nature of Matter
• Let’s try
– An atom has:
•
•
•
•
15 protons
20 protons
19 protons
10 protons
+ 15 electrons =
+ 21 electrons =
+ 18 electrons =
+ 12 electrons=
The Electrical Nature of Matter
• Opposites attract– this is the glue to hold atoms together
– These are chemical bonds.
Ions and Ionic Compounds
• Ions:
– charged atoms;
– atoms that have gained or lost electrons to form
negative or positive ions
• Ionic Compounds: compounds composed of
positive and negative ions
Ions and Ionic Compounds
• Cation: a positively charged ion (Na+)
• Anion: a negatively charged ion (Cl-)
• Polyatomic ion: (many-atoms) an ions made
of two or more bonded atoms (NH4+ or NO3-)
Ions and Ionic Compounds
• Step 1: Write the symbols for the ions side by side,
with the positive ion (or most metallic element) first
• Step 2: Cross over the charge values to give subscripts
• Step 3: Check the subscripts by making sure the total
charge of ions in the compound is zero, simplify
• Step 4: Write the formula
Ions and Ionic Compounds
• Let’s try: Need to use ion chart
• zinc oxide
• aluminum sulfide
• calcium carbonate
Ions and Ionic Compounds
• Naming Compounds
– Nomenclature: the method of naming chemical
compounds
1. write the name of the element having a
positive charge
2. add the name of the negative element
3. the negative element must be modified to
end in –ide
Ions and Ionic Compounds
• Let’s try: Use the chart of ions
• NaI2
• K2O
• BaSO4