LESSON 2: WATER ON EARTH

CHEMISTRY OF WATER

BLUE MARBLE ANIMATION

• THINGS TO CONSIDER WHILE YOU ARE WATCHING….• WHAT OBSERVATIONS CAN YOU MAKE ABOUT THIS ANIMATION OF EARTH

ROTATING?

• DOES THE NORTHERN OR SOUTHERN HEMISPHERE CONTAIN MORE LAND?

• WHICH OCEAN BASIN IS THE LARGEST?

BLUE MARBLE ANIMATION

• THINGS TO CONSIDER WHILE YOU ARE WATCHING….• WHAT OBSERVATIONS CAN YOU MAKE ABOUT THIS ANIMATION OF EARTH

ROTATING?• OCEAN DOMINATES THE SURFACE AREA OF THE GLOBE, LAND APPEARS GREEN AND

BROWN, LINES AND RIDGES IN THE OCEANS, OCEANS ARE INTERCONNECTED, ICE NEAR THE POLES

• DOES THE NORTHERN OR SOUTHERN HEMISPHERE CONTAIN MORE LAND?• NORTHERN HEMISPHERE

• WHICH OCEAN BASIN IS THE LARGEST?• PACIFIC

OCEAN FACTS

• OCEAN COVERS APPROX. 71% OF EARTH’S SURFACE

• FOUR OCEANS

• PACIFIC, ATLANTIC, INDIAN, ARCTIC

• 97% OF EARTH’S WATER IS SALTWATER

• 3% OF EARTH’S WATER IS FRESHWATER

• 1% IS LIQUID

• 2-3% CONTAINED IN GLACIERS AND SEA ICE CAPS IN POLAR REGIONS

EARTH’S 4 “SPHERES” ARE CONSTANTLY CHANGING

• HYDROSPHERE – WATER

• BODIES OF MARINE ANIMALS ARE80% WATER BY MASS

• BIOSPHERE- LIFE

• ATMOSPHERE – AIR

• LITHOSPHERE - LAND

OCEAN AS A RESOURCE

• RENEWABLE RESOURCE – OCEAN REPLENISHES ITSELF NATURALLY OVER RELATIVELY SHORT PERIODS OF TIME

• CONSTANT INFLUX OF WATER FROM RIVERS AND RAIN

• NONRENEWABLE RESOURCE – EXHAUSTED FASTER THAN THEY ARE NATURALLY REPLACED

• EX: NATURAL GAS AND MINERALS

• HUMANS MUST BE CAREFUL TO USE OCEAN RESOURCES WISELY

• EX: OVERFISHING

WATER FOR THOUGHT….

• COMPARE AND CONTRAST SALT WATER AND FRESHWATER.

LAB: FREEZING, MELTING, AND BOILING

WATER CHEMISTRY REVIEW

• FLIP TO APPENDIX B

• ATOMS • BASIC PARTICLE OF A UNIQUE ELEMENT

• NUCLEUS• NEUTRONS: NO ELECTRICAL CHARGE

• PROTONS: +1 CHARGE

• ELECTRONS: -1 CHARGE

• APPROX 90 DIFFERENT NATURALLY OCCURRING ELEMENTS

NEUTRONS

Valence electron shell (outer most shell)

PROTONS

NEUTRONS

ELECTRONS

ISOTOPES

• SCIENTISTS USE VARIATIONS OF ISOTOPES TO RESEARCH EARTH’S CLIMATE OVER MANY YEARS

• STUDIED IN ICE CORE SAMPLES, SEA SHELLS, OR CAVE FORMATIONS

• ISOTOPES ARE VARIATIONS OF THE SAME ELEMENT THAT HAVE SAME NUMBER OF PROTONS, DIFFERENT NUMBER OF NEUTRONS.• EX:

“Heavy Oxygen” 0-18 “Light Oxygen” O-16

Atomic Number (Protons)

8 8

Atomic Mass 18 16

Neutrons 10 8

MOLECULES & BONDING

• OXYGEN AND HYDROGEN ARE USUALLY NOT FOUND ALONE IN A NATURAL STATE

• TWO OR MORE ATOMS BOND TOGETHER TO FORM MOLECULES OR COMPOUNDS

• ATOMS OR MOLECULES ARE MORE STABLE WHEN THEY HAVE A COMPLETE OUTER SHELL

• BONDING – INTERACTIONS BETWEEN 2 ATOMS TO FULFILL OCTET RULE• COVALENT – WHEN 2 ATOMS SHARE ELECTRONS

• IONIC – WHEN 1 ATOM TRANSFERS AN ELECTRON TO ANOTHER ATOM

WATER• ASYMMETRICAL COMBINATION OF 1 OXYGEN AND 2 HYDROGENS

• POLAR

• OXYGEN END SLIGHTLY NEGATIVE WHILE HYDROGEN END SLIGHTLY POSITIVE

• HYDROGEN BONDING

• ATTRACTION OF NEGATIVE OXYGEN OF 1 WATER MOLECULE TO POSITIVE HYDROGEN OF ANOTHER WATER MOLECULE

• LEADS TO COHESION OR “STICKINESS” OF WATER MOLECULES TO ONE ANOTHER

• ALSO LEADS TO ADHESION OR “STICKINESS” OF WATER TO OTHER SUBSTANCES

WATER AND DENSITY

• HYDROGENS BONDS ARE RELATIVELY WEAK IN COMPARISON TO IONIC AND COVALENT

• HOWEVER, COLLECTIVE H BONDS ARE QUITE STRONG

• ONE WATER MOLECULE CAN H BOND TO 4 OTHER WATER MOLECULES

Hydrogen Bond

HOW TEMPERATURE AFFECTS WATER

• WATER MOLECULES ARE SITUATED AS CLOSELY AS THEY CAN BE AT 4˚C.• HIGHEST DENSITY IN LIQUID STATE

• BELOW 4˚C, HYDROGEN BONDING GETS STRONGER AND WATER MOLECULES SPACE OUT• FORMS LATTICE STRUCTURE AND BECOMES SOLID ICE

• WATER EXPANDS AS IT FREEZES

• BECOMES LESS DENSE

• MOST SUBSTANCES ARE MORE DENSE IN SOLID STATE

CHECK FOR UNDERSTANDING

• WITH YOUR PARTNER, ANSWER THE FOLLOWING CHECKPOINTS.

• DISTINGUISH BETWEEN ATOMS AND MOLECULES

• WHAT IS DENSITY? HOW DOES THE POLARITY OF WATER MOLECULES RELATE TO THE DENSITY OF WATER?

GOT IT?

• WITH YOUR PARTNER, ANSWER THE FOLLOWING CHECKPOINTS.

• DISTINGUISH BETWEEN ATOMS AND MOLECULES

• ATOMS ARE THE SMALLEST UNIT OF AN ELEMENT. MOLECULES ARE FORMED WHEN 2 OR MORE ATOMS COMBINE.

• WHAT IS DENSITY? HOW DOES THE POLARITY OF WATER MOLECULES RELATE TO THE DENSITY OF WATER?

• DENSITY IS HOW COMPACT A SUBSTANCE IS – THE MASS OF A SUBSTANCE DIVIDED BY A GIVEN VOLUME. WATER MOLECULES ARE POLAR COVALENT AND THEREFORE FORM HYDROGEN BONDS WITH ONE ANOTHER. THE HYDROGEN BONDS DO NOT ALLOW WATER MOLECULES TO MOVE CLOSER TOGETHER AND BECOME MORE DENSE WHEN WATER GETS COLDER THAN 4˚C. SOLID ICE IS LESS DENSE THAN LIQUID WATER.

THINK BREAK…

• HOW WOULD LIFE IN THE POLAR REGIONS CHANGE IF WATER BEHAVED LIKE A NORMAL SUBSTANCE AT DECREASED TEMPERATURES?

CHANGING PHASES OF MATTER

PHASE CHANGE

• DURING A PHASE CHANGE, TEMPERATURE STAYS THE SAME BUT HEAT ENERGY CONTINUES TO BE ADDED.

• HEAT IS ABSORBED AND MELTS A SOLID INTO A LIQUID

• SAME THING HAPPENS FROM LIQUID TO GAS; THIS IS CALLED VAPORIZATION OR EVAPORATION

• THE HEAT ABSORBED DURING A PHASE CHANGE IS CALLED LATENT HEAT

HEAT CAPACITY

• WATER HAS TREMENDOUS ABILITY TO RESIST CHANGES IN TEMPERATURE

• AMOUNT OF HEAT NEEDED TO RAISE TEMP OF 1G WATER 1˚C IS 1 CALORIE.

• DURING COOLING ENERGY IS TAKEN AWAY OR GIVEN OFF

• FREEZING IS WHEN WATER CHANGES FROM LIQUID TO SOLID

• CONDENSATION WHEN WATER CHANGES FROM GAS TO LIQUID

PHASE CHANGE PRACTICE• SKETCH A PHASE CHANGE DIAGRAM FOR ISOPROPYL ALCOHOL (RUBBING

ALCOHOL)

• FREEZES AT -85.5˚C

• BOILS AT 82.3˚C

• LABEL THE FOLLOWING: SOLID, LIQUID, GAS, FREEZING, MELTING, CONDENSATION, VAPORIZATION

PHASE CHANGE PRACTICE

LAB 2: FLOATING AND SINKING

DENSITY AND MARINE ORGANISMS

• BUOYANCY – THE UPWARD FORCE THAT KEEPS MATERIALS AFLOAT

• HAVE YOU EVER LIFTED UP SOMEONE IN THE WATER? HEAVIER OR LIGHTER?

•WHAT HAPPENS TO THE WATER LEVEL WHEN YOU ADD SOMETHING TO A CUP OF WATER?• THIS IS CALLED DISPLACEMENT

DENSITY AND MARINE ORGANISMS

• THINGS FLOAT BETTER IN SEAWATER THAN FRESHWATER • THIS IS DUE TO DENSITY

• FRESHWATER: 1.00 G/CM3

• SALTWATER: 1.03 G/CM3

DENSITY AND MARINE ORGANISMS

• AQUATIC ORGANISMS USE BUOYANCY AND DISPLACEMENT TO MAINTAIN NEUTRAL BUOYANCY

• EX: PHYTOPLANKTON HAVE OIL DEPOSITS IN SHELLS

• OIL IS LESS DENSE THAN WATER

• EX: JELLYFISH

• ANIMALS THAT ARE 90% WATER, SOME FLOAT ON SURFACE, SOME RELY ON NEUTRAL BUOYANCE TO MAINTAIN POSITION IN WATER COLUMN

• EX: SARGASSUM

• SEAWEED WITH AIR SACS

• ALLOWS FOR AMPLE LIGHT ABSORPTION FOR PHOTOSYNTHESIS

MOON JELLYFISHMoon jellyfish

POLAR BEAR SEA ICE ANIMATION

• MARINE ORGANISMS ARE ALSO AFFECTED BY DENSITY OF WATER’S SOLID FORM

• ANIMALS IN POLAR REGIONS ARE VERY DEPENDENT ON SEA ICE

• POLAR BEARS, PENGUINS, FISH

• INSULATES WATER BELOW

• REFLECTS SUN

GOT IT?

• WHAT IS BUOYANCY? HOW DOES IT ALLOW LARGE OBJECTS LIKE MASSIVE WHALES TO FLOAT?

• DESCRIBE HOW THE STRUCTURE OF THE SARGASSUM HELPS IT TO FLOAT ON WATER.

• HOW DOES THE FACT THAT ICE FLOATS AFFECT MARINE ANIMALS?

• DESCRIBE THE RELATIONSHIP BETWEEN THE MOVEMENTS OF THE POLAR BEAR AND THE SEASONAL CHANGES IN SEA ICE. HOW CAN YOU EXPLAIN THIS RELATIONSHIP?

GOT IT?

• WHAT IS BUOYANCY? HOW DOES IT ALLOW LARGE OBJECTS LIKE MASSIVE WHALES TO FLOAT?• BUOYANCY IS AN UPWARD FORCE EXERTED ON OBJECTS IN A

FLUID. THE BUOYANT FORCE IS EQUAL TO THE WEIGHT OF THE WATER DISPLACED BY THE OBJECT. IN THE CASE OF A LARGE WHALE, THE WHALE DISPLACES A TREMENDOUS AMOUNT OF WATER AND THE BUOYANT FORCE HELPS THE ANIMAL TO FLOAT.

GOT IT?

• DESCRIBE HOW THE STRUCTURE OF THE SARGASSUM HELPS IT TO FLOAT ON WATER.• SARGASSUM HAS GAS-FILLED “BUBBLES” THAT ARE LESS

DENSE THAN WATER, HELPING IT TO FLOAT.

GOT IT?

• HOW DOES THE FACT THAT ICE FLOATS AFFECT MARINE ANIMALS?• ANIMALS SUCH AS WALRUSES, POLAR BEARS, SEALS, AND

PENGUINS CAN REST ON THE ICE BETWEEN SESSIONS OF HUNTING FOR PREY. THE ICE ALSO PROVIDES AN IDEAL PLACE FOR THESE ANIMALS TO RAISE THEIR YOUNG.

GOT IT?

• DESCRIBE THE RELATIONSHIP BETWEEN THE MOVEMENTS OF THE POLAR BEAR AND THE SEASONAL CHANGES IN SEA ICE. HOW CAN YOU EXPLAIN THIS RELATIONSHIP?• THE POLAR BEAR SEEMS TO FOLLOW THE ICE. POLAR BEARS

REST ON THE ICE AS THEY HUNT THEIR PREY, PRIMARILY SEALS.