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 + 15 electrons =• 20 protons + 21 electrons =• 19 protons + 18 electrons =• 10 protons + 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

compounds1. write the name of the element having a

positive charge2. add the name of the negative element3. 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