Water & Solutions Water (H 2 O) 2 hydrogen atom 1 oxygen atoms Covalent bond Essential to all forms of life 70% of the human body ( by weight ) Covers ¾ of the Earth Multiple uses Drinking Cleaning, bathing, etc.
Water & Solutions Properties of Water Acts as a solvent The ability to dissolve molecules Liquid phase has a greater density (g/cc) than in a solid phase Ice floats High specific heat (amount of heat/energy needed to raise 1g 1 degree C ) Needs more energy to heat it What is the application of this concept? Hint: 3/4 of the earth is covered w/ water High latent heat (heat absorbed/released by 1g to change phase) Dissipate large amounts of heat and loose a small amount of water
Water & Solutions
Structure of the Water Molecule 2 hydrogen atoms & 1 oxygen atom Covalent bond or ionic bond ???????? With water – the shared electrons spend more time with the O atoms. Polar molecule forms Water is a hydrogen bond - or - because of the special way in which the oxygen atom and hydrogen bond – water is a very unique substance with very unique characteristics – ie the shape of snowflakes
Water & Solutions Solvent – the component present in the larger amount. Water Solute – the component that is dissolves in the solvent. Sugar
Water & Solutions Dissolving Process Solution Homogeneous mixture Saturated & solubility (or what came first the chicken or the egg) Solubility – the ability to dissolve something The attraction between the molecules or ions of a solvent and solute determines solubility “Remember to wash your hands” Fig 11.5 – p. 280 A chemical tug-of-war
Water & Solutions Concentration of Solutions Concentrated vs diluted The amount of solute in the solution Concentration ratios Parts per million (ppm) Parts per billion (ppb) Sea water – 35 parts / 1000 How concentrated a solution is - is determined by the solutes solubility A key factor of solubility is TEMPERATURE Increase the temp – the greater the solubility Sugar in your tea, coffee, or Kool-Aid
Water & Solutions The concept of saturation The limit at which the solute will dissolve Dissolving is still taking place – you just can not see it.
Water & Solutions Boiling & Freezing Point of Water Boiling Point 100 degrees C 212 degrees F Boiling, and the effect of atmospheric pressure Two forces working against each other Vapor pressure & atmospheric pressure (14.7 lbs / sq. in) What is the principle behind a “pressure cooker”? Freezing Point 0 degrees C 32 degrees F “Fire up the salt trucks - winter is coming !!!!!”
Water & Solutions Acids & Bases A function of the of the number of hydrogen atoms Acid – able to donate a H ion Base – able to accept a H ion pH Scale If pH < 7.0Acid If pH > 7.0Base “Red eyes”