Water

WATER & its unique properties make life possible

Water is ESSENTIAL to life. Water & Living Things Water is ESSENTIAL to life. Living organisms are composed mostly of water. Humans – 76% Jellyfish – 90% Dried beans – 50%

Structure of the Water Molecule Is NOT 180 degrees (H—O—H) IS a little more than a 90 degree angle. Water is Polar – One end is positive, one end is negative.

What creates the HYDROGEN BOND? Oxygen is slightly negative Hydrogen is slightly positive What creates the HYDROGEN BOND? The +/- attraction between the H (+) of one water molecule and the O (-) of the adjacent water molecule.

Polarity & Hydrogen bonds http://videos. howstuffworks

Properties of Water “Universal Solvent” Freezes & Floats Cohesion (Surface tension) Adhesion (Capillary action) High heat of vaporization High heat of fusion

Solution A mixture of… Solute Solvent A substance that is put INTO the solvent to dissolve. Solvent Substance that does dissolves the solute Water - Universal Solvent

SUSPENSION Ever hear… Oil & water don’t mix???

Water is the Universal Solvent BLOOD is 95% water. Ions (NaCl) dissolve in blood (SOLUTION). Water dissolves polar (ionic) substances: SALT (NaCl) Water dissolves non-polar molecules: O2 Helps fish survive CO2 Helps algae survive

Water freezes & floats Liquid ICE Ice is dense less than water Ice has spaces between its water molecules Imagine if ice didn’t float on top of a lake… Ice acts as an insulator to allow the water below to remain a liquid.

Surface Tension Cohesion Water molecules at the surface are not pulled from above. Cohesion This produces a “tension”. The hydrogen bonds pull a water molecule in every direction by adjacent molecules. What substance “broke” the tension in the Water Lab? The water strider bug relies on surface tension to survive.

Water has Capillary Action COHESION – The attraction between water molecules make them “stick” together. ADHESION – The attraction between a water molecule and another substance. CAPILLARY – Any thin long tube. CAPILLARY ACTION – DUE TO cohesion & adhesion Water acts like a magnet and pull itself up against gravity. Living things have capillary tubes: Animals - blood vessels Plants – xylem/phloem From - roots To - leaves

Which substance has greater ADHESIVE properties? COHESION: Water “sticks” to water ADHESION: Water “sticks” to another substance Red dyed water Mercury Which substance has greater ADHESIVE properties?

High heat of vaporization Compared to other liquids it takes a lot of energy to evaporate water. (Less evaporation leaves more water available for living things)

High heat of fusion Large bodies of water change temperature more slowly than air does. (Lakes/ponds stay warmer, longer for living things)