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Water. Earth the Water Planet. Earth the Water Planet. Special Properties of Water. Universal Solvent Transparency Three Physical Phases Density and Temperature High Specific Heat High Heat of Vaporization Low Compressibility “Stickiness” of Water Molecules Viscosity.
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Special Properties of Water • Universal Solvent • Transparency • Three Physical Phases • Density and Temperature • High Specific Heat • High Heat of Vaporization • Low Compressibility • “Stickiness” of Water Molecules • Viscosity
Universal Solvent Solution = A liquid in which two or more substances are homogeneously mixed. Solvent = Fluid portion of a solution into which other substances are dissolved. Solute = A substance that is dissolved into a solvent to produce a solution.
Universal Solvent NaCl (sodium chloride)Dissolving Into Water
Universal Solvent NaCl Dissolving Into Water
Universal Solvent NaCl Dissolving Into Water
Universal Solvent Protein Dissolving Into Water
Solubility of Solids • In general, the solubility of solids increases with increases in temperature.
Solubility of Gases • In general, the solubility of gases decrease with increases in temperature.
Importance to Living Things • Water is the solvent in which most of the chemistry of life takes place.
Importance to Living Things • Aquatic plants are able to live and photosynthesize beneath the surface of the water. • Animals are able to see below the surface of the water. • Changing spectral distribution of light with depth influences physiology and behavior of living things.
liquid solid gas Three Phases of Water
Three Phases of Water solid gas liquid
hydrogen bonds Ice vs Liquid Water ice liquid
Colligative Properties • Dissolved solids increase the boiling point and decrease the freezing point.
Importance to Living Things • Water exists in all three phases at temperatures found on Earth. • If water behaved like substances with similar molecular weight, water would exist only as a gas and it’s likely that the Earth’s gravity wouldn’t retain water.
Density and Temperature • Above 4°C the density of liquid water decreases as the temperature increases. • As the temperature is decreased from 4°C to 0°C, the density decreases. • Water exhibits a density maximum of 1.0 grams/milliliter (g/mL) at 4°C. • Ice is less dense than water.
Importance to Living Things • Ice floats on top of liquid water. • If ice were more dense than liquid water, then ice would sink, leading to a freezing-over of many lakes and streams.
High Specific Heat • 1.0 calories of absorbed heat energy will raise the temperature of 1.0 gram of water by 1.0°C.
Importance to Living Things • Water can buffer the environment and living things against extreme changes in temperature.
High Heat of Vaporization • At 25°C, 1.0 gram of water must absorb 580 calories of heat energy in order to be converted from a liquid to a gas.
Importance to Living Things • Water vapor in the atmosphere moderates the Earth’s climate. • Living things may moderate their body temperatures via evaporation of water from their surfaces (evaporative cooling).
Low Compressibility • Liquid water does not compress significantly into a smaller volume.
Importance to Living Things • Water can provide shape and form to a living thing (hydrostatic skeleton). For some organisms a hydrostatic skeleton may facilitate movement. • Aquatic organisms may swim.
“Stickiness” of Water Molecules • Cohesion • Adhesion • Surface Tension
Cohesion • The binding together of like molecules; the binding together of water molecules to each other via hydrogen bonds.
Adhesion • The binding together of different molecules; the binding of water molecules to other substances via hydrogen bonds.
Cohesion + Adhesion • Capillarity
Importance to Living Things • Cohesion and Adhesion in Water Transport in a Plant
Viscosity Resistance of a Fluid to Flow