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2. MenuPreviousNext 7 - 2 Heat and Heat Capacity nHeat is the kinetic energy in the random movement, or vibration, of individual atoms and molecules in a substance.  The faster molecules move, the more heat there is. Total heat energy is measured based on both the quantity and speed of vibrating molecules. nTemperature measures only how fast the molecules vibrate.  Celsius is most used in science because it is based on water’s physical properties. The Physics of Water Chapter 7 Pages 7-3 to 7-5

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4. MenuPreviousNext 7 - 4 Heat and Heat Capacity (continued) nHeat capacity of a water is the amount of heat energy it takes to change 1g of water by 1°C.  It takes more heat energy to raise water’s temperature than that of most substances.  Therefore water can absorb or release a lot of heat with little temperature change.  Water’s heat capacity affects the world’s climate and weather. Heat is carried to areas that would otherwise be cooler, and heat is absorbed in areas that would otherwise be hotter. The Physics of Water Chapter 7 Page 7-6

5. MenuPreviousNext 7 - 5 Water Temperature and Density nAs water cools it becomes denser. At 3.98°C (39.16°F) it reaches maximum density. nBelow this point, it crystallizes into ice. As water moves into a solid state* it becomes less dense. nIce does not form all at once at the freezing point of 0°C (32°F), but crystallizes continuously until all liquid turns solid. The Physics of Water Chapter 7 Pages 7-7 to 7-11

6. MenuPreviousNext Latent Heat nTemperature does not drop any further until all the liquid water freezes, even though heat continues to leave.  This produces non-sensible heat – a change in heat energy that cannot be sensed with a thermometer. Sensible heat is that which you can sense with a thermometer.  The non-sensible heat lost when water goes from liquid to solid state is called the latent heat of fusion. nLatent heat of vaporization is the heat required to vaporize a substance.  It takes more latent heat to vaporize water than to freeze it because when water freezes only some of the hydrogen bonds break.  When it vaporizes, all the hydrogen bonds must break, which requires more energy. 7 - 6

7. MenuPreviousNext 7 - 7 Thermal Inertia nThe tendency of water to resist temperature change is called thermal inertia. nThermal equilibrium means water cools at about the same rate as it heats. nThese concepts are important to life and Earth’s climate because seawater acts as a global thermostat, preventing broad temperature swings. nTemperature changes would be drastic between night and day and between summer and winter. nWithout the thermal inertia, many of the organisms on Earth could not survive. The Physics of Water Chapter 7 Pages 7-11 & 7-12

8. MenuPreviousNext 7 - 8 Ocean Water Density nSeawater density varies with salinity and temperature. This causes seawater to stratify, or form layers. nDense water is heavy and sinks below less dense layers. The three commonly found density layers are:  1. Surface zone – varies in places from 0 to 500m. In general it extends from the top to about 100m. This zone accounts for about only 2% of the ocean’s volume.  2. Pycnocline – separates the surface zone from the deep zone. It needs a temperature or salinity difference to exist. This zone makes up about 18% of the ocean’s volume.  3. Deep zone – lies below the pycnocline. It is a very stable region of cold water beginning deeper than 1,000m. The deep zone makes up about 80% of the ocean’s volume. The Physics of Water Chapter 7 Pages 7-13 & 7-14

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10. MenuPreviousNext 7 - 10 Light nWater scatters and absorbs light. When light reaches the water’s surface, some light penetrates, but, depending on the sun’s angle, much may simply reflect back out of the water.  Within the water, light reflects off light-colored suspended particles. Dark colored suspended particles and algae absorb some of the light.  Water molecules absorb the energy, converting light into heat.  Water absorbs colors at the red end of the spectrum more easily than at the blue end. How Water Physics Affect Marine Life Chapter 7 Pages 7-16 to 7-20

11. MenuPreviousNext Light (continued) nTwo zones exist with respect to light penetration:  1. Photic Zone – where light reaches can be as deep as 200m. The photic zone has two subzones. nEuphotic Zone – the upper portion where photosynthesis occurs nDysphotic Zone – not enough light for photosynthesis  2. Aphotic Zone – it makes up the vast majority of the oceans; no light and little life 7 - 11

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13. MenuPreviousNext 7 - 13 Sound nSound travels five times faster in water than in air.  It travels through warm water faster than cool…but it travels faster in deep water due to pressure.  Sound bounces off suspended particles, water layers, the bottom and other obstacles.  Sound travels much farther through water than light does.  Sound is eventually absorbed by water as heat. nBecause sound travels so well in water, marine mammals use echolocation to sense an object’s size, distance, density, and position underwater. How Water Physics Affect Marine Life Chapter 7 Pages 7-22 to 7-24

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15. MenuPreviousNext 7 - 15 Temperature nCompared to land-based climates, marine organisms live in a much less challenging environment with respect to temperature range.  Ectotherm – An organism who's internal temperature changes with seawater temperature. Commonly called “cold- blooded.”  Endotherm – Organisms that have an internal temperature that varies, but remains 9°-16°C (48.2°- 60.8°F) warmer than the surrounding water.  Homeotherm – Have an internal temperature that is relatively stable. They are called “warm-blooded”; marine mammals and birds are in this category. nTemperature affects metabolism – the higher the temperature within an organism the more energy-releasing chemical processes (metabolism) happen. How Water Physics Affect Marine Life Chapter 7 Pages 7-21 & 7-22

16. MenuPreviousNext 7 - 16 Pressure nPressure exerted by water is called hydrostatic pressure. It’s simply the weight of the water.  At 10 meters (33 feet) hydrostatic pressure is equal to atmospheric pressure  A marine organism living at 10 meters (33 feet) experiences twice the pressure present at sea level. Pressure increases 1 bar for each additional 10 meters (33 feet). nHydrostatic pressure doesn’t affect marine organisms because it is the same inside the organism as outside.  Living tissue is made primarily of water, which (within limits) transmits pressure evenly. Since it’s in balance, pressure doesn’t crush or harm marine organisms.  Hydrostatic pressure is primarily an issue only for organisms that have gas spaces in their bodies. How Water Physics Affect Marine Life Chapter 7 Pages 7-25 to 7-27