The Sea Around Us Lecture 3: Properties of Water: The Wonder Substance Todays music: Bill Nye Water Cycle Jump! NIGHTWISH - The Islander Ron Pope - A drop in the ocean The Presets - Girl and the sea From: A Gentle Introduction to WaterThanks to Hannah P., Kara D. & Daisha M. Lecture Notes and Review QuestionsLecture Notes and Review Questions TA Office Hours (T & W 2-3) On-line Assignment 1 is due tonight by 11pm Homework 1 due Jan 28 Cell Phone Recycling Songs and Questions (Angel) Florida couple planning for life under the seacience/story.aspx?storyid= &catid=67 World Ocean CouncilWorld Ocean Council See link for Internship Program. Current progress: underseacolony.com/prime/mainhub_revA.html Read your book anywhere and everywhere! True (ocean) love!!? Today is the first in-class iClicker exercise for credit A)Full credit if you answer 80% or more of the questions B) Bonus points if you get the correct answer for 80% of more of the questions C) If there are 8 questions and you answer at least 7 of them youll get full credit (100%) D) If there are 8 questions and you answer at least 7 of them correctly youll get a 5% bonus (105%) E) All of the above (this is the correct answer, choose E!) Water in the Oceans --and why we should be concerned about the physical properties of water Importance to Physical & Biological Processes Waters unique physical properties cause a buffering of Earths surface and environmental changes, which promotes continuity of life on Earth The physical properties of water determine how oceans circulate, how heat is transferred by the ocean and atmosphere, and the way waves work. Water Promotes Continuity of Life on Earth Low viscosity rapid flow to equalize pressure differences Low compressibility Small change in volume for a change in pressure High heat capacity cools/warms slowly relative to land aids in heat retention & transport minimizes extremes in temperature helps to maintain uniform body temps High latent heat of evaporation/precipitation very important for heat transfer between ocean & atmosphere (main source of energy for hurricanes!) High surface tension allows wind energy to be transmitted to sea surface allows cells to hold shape --and life to form controls the behavior of water drops Properties of Water: Surface Tension, Viscosity, Compressibility Viscosity: Is the resistance to shear motion Increases as water cools Is low for water, compared to say, ketchup Low viscosity liquids pour or stir easily Ketchup has high viscosity Water has low viscosity Properties of Water: Surface Tension, Viscosity, Compressibility Compressibility (can you squooosh it?) is: Very low for water The change in volume for a change in pressure Think about: In the ocean: pressure increases by 1 atm. (14.5 psi) for every 10 m increase in depth at 4000 m, a liter of water (at the surface) is only ~ 2% smaller Sea level would be 37m higher if water were totally incompressible After Compression before Properties of Water: Surface Tension, Viscosity, Compressibility Surface tension or capillary force (highest of all liquids) cohesion of liquid surface- intermolecular forces water forms weak "elastic" membrane increases as water cools decreases with increasing salt content meniscus Surface tension is what holds water drops together and determines the shape of waves. Ripples and small waves are generated by wind energy and the surface tension of water. Physical Properties of Water. Check out Water Drop at 2000 Frames per Second From Discovery Channel's series 'Time Warp' where MIT scientist and teacher Jeff Lieberman and digital-imaging expert Matt Kearney use the latest in high-speed photography to turn never-before-seen wonders into an experience of beauty and learning. Physical Properties of Water: The Wonder Substance Molecular Structure and Organization Bonding of hydrogens to oxygen creates a "polar" molecule. Water molecule: 105 angle unequal charge distribution: Polar Molecular Structure and Organization: Clustering of water molecules What causes it? hydrogen bonds (weak interaction ~10% of covalent strength) This property creates Surface Tension Liquid water; bonds are constantly breaking and reforming each bond lasts a few trillionths of a second high proportion of molecules bonded at any instant Water Promotes Continuity of Life on Earth Low viscosity rapid flow to equalize pressure differences High surface tension allows wind energy to be transmitted to sea surface allows cells to hold shape --and life to form controls the behavior of water drops High heat capacity cools/warms slowly relative to land aids in heat retention & transport minimizes extremes in temperature helps to maintain uniform body temps High latent heat of evaporation very important in heat/water transfer in atmosphere Properties of Water Unusual Properties--compare other liquids Heat capacity (high) only ammonia (NH3) higher H 2 0 much higher heat capacity than rock or steel Heat Capacity or Specific heat: What is it? Ability of a material to store heat Heat needed to change the temperature of a given mass of water (1 gram or 1 kilogram) by 1 degree C For Water: heat capacity is: 1 cal per gram per deg. Celsius: 1cal/(gm C) 1 calorie is the heat energy needed to raise 1 gm by 1C 1 calorie 4.19 J (heat capacity of water is 4190 J/Kg C) Need 41,900 J to raise the temperature of 1 kg (1 liter) of water from 0 to 100 C 3 phases of materials Heat Capacity Heat required to change the temperature (by 1 deg.) of a given mass Heat input (J/kg or cal/gram) Temperature (C) Liquid water Rock & Soil 4190 Kg C J Heat capacity and phase changes: ice (solid) water (liquid) vapor or steam (gas) Heat input (cal/gram) Temperature (C) Liquid water Ice Vapor Latent Heat Heat needed to change phase (from solid to liquid, liquid to gas, liquid to solid, etc.) Latent heat of vaporization or condensation 540cal/gm Latent heat of fusion or melting 80cal/gm Ice + liquid vapor+ liquid Heat input (J/kg or cal/gram) Temperature (C) Higher Heat Capacity Lower Heat Capacity Heat Capacity Heat required to change a given mass by a given temp. J/kg or cal/gram Pepsi Latent Heat and Changes of State Latent heat of fusion (or melting) Heat to form or melt ice (liquid to solid phase) 333 kJ/kg (80 calories/gram) Latent heat of vaporization (or precipitation) Heat to vaporize (boil) a liquid or condense liquid from a gas phase 2260 kJ/kg (540 calories/gram) Evaporation of water from the surface can occur at any temperature. However, it takes more energy to evaporate at low T than to boil off vapor once water reaches 100C The high heat capacity of water means that it heats up and cools off more slowly than land. Latent heat is a key factor in Hurricane development and sustainability. Properties of Water: Heat Capacity What is heat capacity? Why is it so high for H 2 0? Adding heat to water: speeds up molecules break bonds Hence, less warming or less evaporation than expected When heat is removed from water: bonds form and restructure, material condenses (e.g., gas to liquid) energy is released via bonds formation Energy release causes heating and thus temperature decrease is smaller than expected Density of Water Fresh water reaches maximum density at 3.98 C Density= 1,000 kg/m 3 (1kg/liter) Density decreases as water is heated above 4C At 20 C, density of pure H 2 O is kg/m 3 Density of Fresh Water & Ice Ice is less dense than water. Ice at 0 C is kg/m 3 Ice has an open hexagonal structure Density of ice is about 91% of liquid water Water molecular structure Ice molecular structure Water Promotes Continuity of Life on Earth Low viscosity rapid flow to equalize pressure differences High surface tension allows wind energy to be transmitted to sea surface allows cells to hold shape --and life to form controls the behavior of water drops High heat capacity cools/warms slowly relative to land aids in heat retention & transport minimizes extremes in temperature helps to maintain uniform body temps High latent heat of evaporation very important in heat/water transfer in atmosphere Heat (cal, or Joules) Temperature (C) water Heat, Temperature and Changes of Phase Ice changes to water (melts!) at 0 C If we add heat to water (or ice) the temperature rises, this is known as sensible heat Heat is required to change the phase of a substance (for example, ice to water); this is known as latent heat Ice Latent heat Sensible heat Heat Capacity Heat required to change the temperature (by 1 ) of a given mass Heat input (J/kg or cal/gram) Temperature (C) Liquid water Rock & Soil Pepsi Heat input (J/kg or cal/gram) Temperature (C) Liquid water Rock & Soil Heat Capacity Heat required to change the temperature (by 1 ) of a given mass Heat input (J/kg or cal/gram) Temperature (C) Liquid water Rock & Soil Heat Capacity Heat required to change the temperature (by 1 ) of a given mass Heat input (J/kg or cal/gram) Temperature (C) Liquid water Rock & Soil Heat Capacity Heat required to change the temperature (by 1 ) of a given mass Heat input (J/kg or cal/gram) Temperature (C) Liquid water Rock & Soil Heat Capacity Heat required to change the temperature (by 1 ) of a given mass Heat input (J/kg or cal/gram) Temperature (C) Liquid water Rock & Soil Heat Capacity Heat required to change the temperature (by 1 ) of a given mass Heat capacity and phase changes: ice (solid) water (liquid) vapor or steam (gas) Heat input (cal/gram) Temperature (C) Liquid water Ice Vapor Latent Heat Heat needed to change phase (from solid to liquid, liquid to gas, liquid to solid, etc.) Latent heat of vaporization or condensation 540cal/gm Latent heat of fusion or melting 80cal/gm Ice + liquid vapor+ liquid Density of Water Fresh water reaches maximum density at 3.98 C Density= 1,000 kg/m 3 (1kg/liter) Density decreases as water is heated above 4C At 20 C, density of pure H 2 O is kg/m 3