water & solutions
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Water & Solutions. Water is a unique molecule necessary for life. found in all cells and surrounds all cells. Polarity. an uneven distribution of shared electrons within the molecule. Hydrogen Bonds. a weak chemical attraction between polar molecules - PowerPoint PPT PresentationTRANSCRIPT
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Water & Solutions• Water is a unique molecule necessary
for life.• found in all cells and surrounds all cells
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Polarity• an uneven distribution of shared
electrons within the molecule
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Hydrogen Bonds• a weak chemical attraction between
polar molecules– the attraction between the positively
charged hydrogen of water and the negative charge that exists on other polar molecules including water itself
– due to water’s polarity
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Cohesion and Adhesion• Cohesion
– attraction between molecules of the same substance
• Adhesion– attraction between molecules of different
substances
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Water & Solutions
See Figure 5 on textbook page 31
Hydrogen Bonding in Water
Is this cohesion or adhesion?
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Surface Tension• property of the surface of a liquid to resist
an external force– the surface can stretch and will not break
easily– caused by cohesion
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Water & Solutions
Surface Tension
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Capillary Action• process in which water molecules move up
through a narrow tube– the attraction of water to the walls of the tube
and to the other water molecules around it pulls the water up more strongly than gravity pulls it down
– caused by adhesion and cohesion
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Water & SolutionsCapillary Action
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Density• liquid water has a density of 1 g/mL
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Solid form less Dense than Liquid form
• water is rare in that its solid form (ice) is less dense than its liquid form water
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Solid form less Dense than Liquid Form
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Solid form less Dense than Liquid form
• water is rare in that its solid form (ice) is less dense than its liquid form water– ice floats in water
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Universal Solvent• “like dissolves like”• water is able to dissolve ionic compounds and
other polar compounds, but not nonpolar compounds
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Universal Solvent• Solution
– mixture of two or more substances in which the solute molecules are evenly distributed in the solvent
• Solute– substance that is dissolved
• Solvent– substance that does the dissolving
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Ionic vs. Polar vs. Nonpolar• Ionic
– substances made of oppositely charged ions held together by ionic bonds
• Polar– substances with charged ends held together by
covalent bonds• Nonpolar
– substances with no charges held together by covalent bonds
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Water & Ionic SubstancesWhy is water able to dissolve salt?
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Water & Ionic SubstancesSalt is ionic (made of charged particles) and water is polar (has charged ends).
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Water & Polar SubstancesWhy is water able to dissolve sugar?
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Water & Polar SubstancesSugar is polar (has charged ends) and
water is polar (has charged ends).
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Water & Nonpolar Substances
Why does vegetable oil separate from water when they are mixed in the same container?
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Water & Nonpolar Substances
Why does vegetable oil separate from water when they are mixed in the same container?
Vegetable oil is nonpolar (no charged ends), and water is polar (has charged ends).
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Specific Heat• water has a high specific heat
– specific heat – the amount of heat required to raise 1 gram of a substance 1 degree Celsius
• it takes a lot of energy to heat up or cool down water
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Water & Solutions• Pure water will ionize in the following
way to create hydrogen, and hydroxide ions.
• because of this, water has a neutral pH
H2O H+ + OH-
water hydrogenion
hydroxideion
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Water & Solutions• pH - a system to measure the
concentration of H+ ions in a solution• Acids
– H+ > OH- – pH values < 7
• Bases– H+ < OH- – pH values > 7
• Neutral– H+ = OH- – pH values = 7– pure (distilled) water
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Water & Solutions
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Water & Solutions• each whole number represents a factor
of 10 on the scale– Ex: A solution with a pH of 5 is 10 times
as many hydrogen ions as one with a pH of 6
– Ex: How much more acidic is a solution with a pH is 2 than one with a pH is 5?• 2 3 = 10 times• 3 4 = 10 times• 4 5 = 10 times• 10x10x10 = 1,000 times more acidic!
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Water & Solutions
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Water & Solutions• Buffers
– Weak acids or bases that prevent sudden changes in pH in living organisms