PROPERTIES OF WATER WATER COVERS OF EARTHS SURFACE

PROPERTIES OF WATER

WATER • COVERS ¾ OF EARTH’S SURFACE • MOST ABUNDANT COMPOUND IN LIVING THINGS • LIQUID AT THE TEMPS FOUND OVER MUCH OF THE EARTH’S SURFACE • EXPANDS AS IT FREEZES • ICE FLOATS

THE WATER MOLECULE • OXYGEN ATOM HAS A STRONGER ATTRACTION FOR ELECTRONS • GREATER PROBABILITY OF FINDING THE SHARED ELECTRONS NEAR THE OXYGEN THAN THE HYDROGEN • CREATES A POLAR MOLECULE: • OXYGEN END HAS A SLIGHT NEGATIVE CHARGE • HYDROGEN END HAS A SLIGHT POSITIVE CHARGE

HYDROGEN BONDS • POLAR MOLECULES CAN ATTRACT EACH OTHER • HYDROGEN BONDS FORM BETWEEN THE HYDROGEN ATOM ON ONE WATER MOLECULE AND THE OXYGEN ATOM ON ANOTHER • NOT AS STRONG AS COVALENT OR IONIC BONDS • RESPONSIBLE FOR MANY OF WATER’S SPECIAL PROPERTIES

COHESION • ATTRACTION BETWEEN MOLECULES OF THE SAME SUBSTANCE • WATER’S COHESION CAUSES MOLECULES ON THE SURFACE OF WATER TO BE DRAWN INWARD • FORMING BEADS • THIS “SURFACE TENSION” ALLOWS SOME INSECTS AND SPIDERS TO WALK ON A POND’S SURFACE

ADHESION • ATTRACTION BETWEEN MOLECULES OF DIFFERENT SUBSTANCES • WATER MOLECULES ATTRACTED TO GLASS, SO SURFACE OF WATER IN A GRADUATED CYLINDER DIPS IN THE CENTER • ALSO CAUSES WATER TO RISE IN A NARROW TUBE AGAINST GRAVITY (CAPILLARY ACTION) • IN PLANTS, DRAWS WATER OUT OF ROOTS UP INTO STEMS & LEAVES

MIXTURE • COMPOSED OF TWO OR MORE ELEMENTS OR COMPOUNDS THAT ARE PHYSICALLY MIXED TOGETHER BUT NOT CHEMICALLY COMBINED • SALT & PEPPER • SUGAR & SAND • EARTH’S ATMOSPHERE • TWO TYPES OF MIXTURES WITH WATER solutions suspensions

SOLUTIONS • MIXTURE OF 2 OR MORE SUBSTANCES IN WHICH THE MOLECULES ARE EVENLY DISTRIBUTED • SOLUTE: SUBSTANCE THAT IS DISSOLVED • SOLVENT: SUBSTANCE IN WHICH THE SOLUTE DISSOLVED • WATER: GREATEST SOLVENT ON EARTH • DUE TO ITS POLARITY

SUSPENSIONS • MIXTURES OF WATER AND NONDISSOLVED MATERIAL • BLOOD: A SOLUTION AND A SUSPENSION • MOSTLY WATER WITH MANY DISSOLVED COMPOUNDS • CONTAINS CELLS & OTHER UNDISSOLVED PARTICLES THAT REMAIN IN SUSPENSION

ACIDS, BASES, AND p. H • A WATER MOLECULE CAN REACT TO FORM IONS

THE p. H SCALE • INDICATES THE CONCENTRATION OF H+ IONS IN SOLUTION • RANGES FROM 0 -14 • AT A p. H OF 7, THE CONCENTRATION OF H+ IONS AND OH- IONS IS EQUAL • PURE WATER • EACH STEP ON THE p. H SCALE REPRESENTS A FACTOR OF 10

ACIDS • ANY COMPOUND THAT FORMS H+ IONS IN SOLUTION • HIGHER CONCENTRATION OF H+ IONS THAN PURE WATER • p. H VALUES BELOW 7 • THE FARTHER AWAY FROM 7, THE STRONGER THE ACID IS

BASES • COMPOUND THAT PRODUCES HYDROXIDE (OH-) IONS IN SOLUTION • ALSO CALLED ALKALINE • CONTAIN LOWER CONCENTRATIONS OF H+ IONS THAN PURE WATER • p. H VALUES ABOVE 7 • THE FARTHER AWAY FROM 7, THE STRONGER THE BASE IS

BUFFERS • WEAK ACIDS OR BASES THAT CAN REACT WITH STRONG ACIDS OR BASES TO PREVENT SHARP, SUDDEN CHANGES IN PH • MAINTAIN HOMEOSTASIS IN THE BODY