the chemistry of water. water water, water everywhere if you have ever seen a photograph of earth...
DESCRIPTION
Water 1. Working with a partner, make a list of ten things that have water in them. 2. Exchange your list for the list of another pair of students. Did your lists contain some of the same things? Did anything on the other list surprise you? 3. Did either list contain any living things?TRANSCRIPT
The Chemistry of Water
Water
Water, Water EverywhereIf you have ever seen a photograph of Earth from space,
you know that much of the planet is covered by water. Water makes life on Earth possible. If life as we know it exists on some other planet, water must be present to
support that life.
Water1. Working with a partner, make a list of ten things that have water
in them.
2. Exchange your list for the list of another pair of students. Did your lists contain some of the same things? Did anything on the other list surprise you?
3. Did either list contain any living things?
Water
Makes life possibleLife on earth probably evolved in waterLiving cells are 70% to 90% waterWater covers about 75% of the earthOnly substance on earth that exists in each of the 3 physical states of matterPolar molecule held together by hydrogen bond
Hydrogen Bond
Hydrogen bond
Formed when a hydrogen atom covalently bonds to another atom
The + charge of the H will attract to the – charge of the O
Hydrogen Bonding
Properties of Water
1. Cohesion: Stick to itself force2. Adhesion: Stick to other things force
Properties of Water3. Capillary Action: Water rising through a
small tube defying gravity*The smaller the tube the higher the water
climbs*
Properties of Water
*Above properties aide in the upward movement of water
in plants
Water Properties Cont.
4. Surface Tension: Measure of how difficult it is to stretch or break the surface of a liquid.Water has a greater surface tension than
most liquid
Ex] Small insects are able to walk on water
Water Properties Cont.
5. Expansion of water as it freezesBecomes less densePrevents bodies of
water from freezing solid from bottom up
Ice forms on surface releasing heat to the water below and insulating it.
Water Properties Cont.
6. High Specific Heat: Ability of water to absorb a lot of heat energy without having its temperature increase by very much
Ex] moderates climatesBECAUSE OF WATER'S HIGH SPECIFIC HEAT CAPACITY, CITIES LOCATED NEXT TO LARGE BODIES OF WATER TEND TO STAY WARMER IN THE WINTER AND COOLER IN THE SUMMER. DURING THE EARLY SUMMER MONTHS, FOR INSTANCE, CHICAGO'S LAKEFRONT STAYS COOLER THAN AREAS FURTHER INLAND. THIS IS BECAUSE THE LAKE IS COOLED FROM THE WINTER'S COLD TEMPERATURES AND SNOW RUNOFF.
Water Properties Cont.
7. High Heat of Vaporization: Amount of energy needed to transform a liquid to a gas.
Takes a lot of heat to evaporate just a little waterEX] allows water to remain in smaller lakes and ponds in
the summer
Water Properties Cont.
8. High heat of Fusion: Amount of energy taken from water to transform liquid to solid
Lakes and streams take longer to freeze allowing wildlife more time to adapt.
Mixtures
Combination of substances in which the individual substances retain their own
propertiesNo chemical bondsA. Can be separated by physical means
Types of mixtures
1. Solution: Homogenous (same throughout) mixture of 2 or more substances in which one substance (the solute) dissolves in another substance (the solvent).
A. Will not settle outB. Transparent
Ex] salt water, sugar water, Kool-Aid
Types of mixtures
2. Suspension:Mixture with larger particles than in a solution, suspended in another medium.
A. Will settle outB. CloudyC. Particles may not be homogenous
Ex.] Clay in water, Liquid “pink stuff” (amoxicillin)
Types of mixtures
3. Colloid: Have particles that are larger than a solution, but smaller
than a suspension. Share characteristics of both solution & suspension.
A. Do not settle outB. Usually cloudyEx] Mayonnaise, milk, cytoplasm, paint, blood serum, Jell-O
Mixtures
Acids & Bases
pHMeasure of how acidic or how basic
something isRegulator of every reaction in a living
system
Acids
Taste sourForms H+ ions in solutionRecognized by the chemical formula (beginning with an
H)
Ex] HCl, HNO3
Base
Bitter tasteSlippery feelForms OH- (hydroxide) ions in solution
Ex] KOH, NaOH
pH Scale
Oven cleaner
Bleach
Ammonia solution
Soap
Sea water
Human bloodPure waterMilkNormalrainfall
Acid rainTomatojuice
Lemon juice
Stomach acid
Neutral
Incr
easi
ngly
Bas
icIn
crea
sing
ly A
cidi
c
Acids & Bases
Buffers: Minimize pH changes: absorb or release H+ ions
Salts:Formed when acids & bases are mixed in solution
The H+ ions combine with the OH- ions forming water.The salt is formed from the anion & cation that remain