OCE Ch6

43. What effect do temperature and pressure have on the speed of sound when entering seawater? a. The speed of sound increases as temperature and pressure decrease. b. The speed of sound increases with temperature increases, but decreases with pressure. c. The speed of sound decreases as temperature and pressure decrease. d. The speed of sound is impacted by pressure but not temperature. e. The speed of sound remains unchanged from the surface to the deep ocean.

ANSWER: c NOTES: The speed of sound in seawater increases as temperature and pressure increase. Sound travels faster at the warm ocean surface than it does in deeper, cooler water. Its speed decreases with depth, eventually reaching a minimum at about 1,000 meters. Below that depth, however, the effect of increasing pressure offsets the effect of decreasing temperature, so speed increases again. Near the bottom of an ocean basin, the speed of sound may actually be higher than at the surface.

35. The deep zone comprises about ____ of total ocean volume. a. 10% b. 30% c. 50% d. 80% e. 95%

ANSWER: d NOTES: Below the pycnocline lies the deep zone of cold, dense water—about 80% of total ocean volume.

17. What are bonds that are formed by the sharing of paired electrons? a. covalent bonds b. proton bonds c. cohesion bonds d. ionic bonds e. adhesion bonds

ANSWER: a NOTES: The bonds formed by shared pairs of electrons are known as covalent bonds.

13. Only blue and green wavelengths pass through water in any appreciable quantity or distance. a. True b. False

ANSWER: True NOTES: Blue and green wavelengths are 99% absorbed at depths of 254 m and 113 m, respectively.

1. The influence of water on global temperatures, due to water's thermal characteristics, prevents broad swings of temperature during the day and night. a. True b. False

ANSWER: True NOTES: Liquid water's thermal characteristics prevent broad swings of temperature during day and night, and, through a longer span, during winter and summer. Heat is stored in the ocean during the day and released at night.

41. How is sound transmitted through a medium? a. By rapid vibrations of molecules. b. By rapid temperature changes in a medium. c. By rapid pressure changes in a medium. d. By rapid random movements. e. By rapid density changes in a medium.

ANSWER: c NOTES: Sound is a form of energy transmitted by rapid pressure changes in an elastic medium. Sound intensity decreases as it travels through seawater because of spreading, scattering, and absorption.

3. Heat and temperature are synonymous terms. a. True b. False

ANSWER: False NOTES: Heat and temperature are related concepts, but they are not the same thing. Heat is energy produced by the random vibration of atoms or molecules. Heat is a measure of how many molecules are vibrating and how rapidly they are vibrating. Temperature records only how rapidly the molecules of a substance are vibrating.

7. When saltwater freezes, the sea salts are incorporated into the ice matrix. a. True b. False

ANSWER: False NOTES: Seawater's density increases smoothly with decreasing temperature until it freezes. The crystals that form are pure water ice, with the seawater salts excluded. The leftover cold, salty water is very dense. Some of this water may be trapped among the ice crystals, but most is free to fall toward the seabed, pulled rapidly downward by its great density.

11. Seawater density increases with increasing salinity and decreasing pressure. a. True b. False

ANSWER: False NOTES: Seawater's density increases with increasing salinity, increasing pressure, and decreasing temperature.

8. The continuous removal of heat from water corresponds to a consistent decrease in temperature. a. True b. False

ANSWER: False NOTES: The removal of heat does not correspond to a steady drop in temperature. The heat removal does lower the temperature, but the temperature stops when there is a phase change. Even though heat continues to be removed, the water will not get colder until all of it has changed state from liquid (water) to solid (ice). Heat may therefore be removed from water when it is changing state (that is, when it is freezing) without the water dropping in temperature. Indeed, the continued removal of heat is what makes the change in state possible.

4. The energy requirements of water's latent heat of fusion are the same as water's latent heat of vaporization. a. True b. False

ANSWER: False NOTES: Water's latent heat of fusion requires only 80 calories per gram; whereas, its latent heat of vaporization requires 540 calories per gram. Only a small percentage of hydrogen bonds are broken when ice melts, but all of them must be broken during evaporation. Breaking these bonds requires additional energy in proportion to their number.

15. Sound in the ocean has been used to measure ocean temperatures. a. True b. False

ANSWER: True NOTES: In 1993, nearly 100 researchers at 13 institutions began a 5-year US$40 million experiment to measure ocean temperature within a few thousandths of a degree using sound. Since sound travels more rapidly through warmer water, water temperature differences can be calculated by recording the time taken for sound to reach receivers around the world. The temperature of the ocean is an important measure of potential global warming.

9. Over the past 40 years, the tropical ocean has become warmer and saltier, while water in the far north and south has become fresher. a. True b. False

ANSWER: True NOTES: Over the past 40 years the tropical ocean shallower than 1,000 meters has become warmer and saltier, while water in the far north and south has become fresher. The world's heat-driven cycle of evaporation and precipitation seems to have become between 5% and 10% faster during that time, increasing both the rate of water evaporation in the tropics and the amount of precipitation in the polar regions.

6. Amount of heat generated does not always indicate higher temperature. a. True b. False

ANSWER: True NOTES: Recall the example in the book about a candle and a bathtub. Which has a higher temperature: a candle flame or a bathtub of hot water? The flame. Which contains more heat? The tub. The molecules in the flame vibrate very rapidly, but there are relatively few of them. The molecules of water in the tub vibrate more slowly, but there are a great many of them, so the total amount of heat energy in the tub is greater.

14. Scattering occurs more in water than air due to the greater density of water. a. True b. False

ANSWER: True NOTES: Scattering occurs as light is bounced between air or water molecules, dust particles, water droplets, or other objects before being absorbed. The greater density of water (along with the greater number of suspended and dissolved particles) makes scattering more prevalent in water than in air.

5. The latent heat of seawater is different than pure water due to the dissolved solids and gases present. a. True b. False

ANSWER: True NOTES: The solids dissolved in seawater change its thermal characteristics, lowering its latent heat by about 4%. Only 0.96 calorie of heat energy is needed to raise the temperature of 1 gram of seawater by 1°C.

10. The most stable layer, in terms of temperature and density, is the mixed layer. a. True b. False

ANSWER: True NOTES: The surface zone, or mixed layer, is the upper layer of ocean. Temperature and salinity are relatively constant with depth in the surface zone because of the action of waves and currents.

12. Sound and light waves bend because they travel at different speeds in different media. a. True b. False

ANSWER: True NOTES: When a light wave or a sound wave leaves a medium of one density and enters a medium of a different density at an angle other than 90°, it is bent from its original path. The reason for this bending is that light or sound waves travel at different speeds in the different media.

2. The polarity of water makes it able to dissolve many compounds. a. True b. False

ANSWER: True NOTES: When water comes into contact with compounds whose elements are held together by the attraction of opposite electrical charges (most salts, for example), the polar water molecule will separate that compound's component elements from each other. This explains why water can easily dissolve so many other compounds.

19. What is responsible for the capillary action of water? a. latent heat of fusion b. thermal inertia and surface tension c. adhesion and cohesion d. latent heat of vaporization e. Density

ANSWER: c NOTES: Cohesion and adhesion are the causes of capillary action, the tendency of water to spread through a towel when one corner is dipped in water.

23. Ice is effective at cooling drinks because of the ____. a. sensible heat loss of water b. heat capacity of water c. latent heat of fusion d. diffusion of heat energy e. latent heat of vaporization

ANSWER: c NOTES: Latent heat of fusion is also a factor during thawing. When ice melts, it absorbs large quantities of heat (the same 80 calories per gram), but it does not change in temperature until all the ice has turned to liquid. This explains why ice is so effective in cooling drinks.

25. What is the only substance to have a higher heat capacity than liquid water? a. acetone b. gasoline c. ammonia d. ice e. Alcohol

ANSWER: c NOTES: Of all common substances, only liquid ammonia has a higher heat capacity than liquid water.

36. Which is a characteristic of thermoclines? a. Tropical thermoclines are shallower than those at higher latitudes. b. Thermoclines tend to be identical in form. c. Polar waters tend to lack thermoclines. d. Thermoclines are more pronounced in the high latitudes. e. Thermoclines are not affected by seasons.

ANSWER: c NOTES: Polar waters, which receive relatively little solar warmth, are not stratified by temperature and generally lack a thermocline because surface water in the polar regions is nearly as cold as water at great depths.

24. During a change in state of water, which is true? a. As temperature increases (or decreases), heat stays the same. b. As heat is applied (or removed), temperature increases (or decreases). c. As heat is applied (or removed), temperature stays the same. d. As heat is applied (or removed), density stays the same. e. As temperature increases (or decreases), density stays the same.

ANSWER: c NOTES: When water changes state (freezes, boils, thaws) heat is applied, or removed, but temperature does not change until all the water has changed state.

42. What is a shadow zone? a. A zone that is unable to be penetrated by sound waves due to the density of seawater b. A zone that is unable to be penetrated by light waves due to deep depths c. A zone in front of ships and submarines that creates a converging blind spot for sound waves d. A zone where the divergence of sound waves creates a region that has little sound energy penetration e. A zone that is unable to be penetrated by light waves due to high scattering

ANSWER: d NOTES: An object beyond the area of divergence may be undetectable; it would be within a shadow zone, a region into which very little sound energy penetrates.

20. What important characteristic of pure water gives it a pale blue color? a. large oxygen atoms b. surface tension c. adhesion to other solids d. hydrogen bonds e. thermal inertia

ANSWER: d NOTES: Hydrogen bonds are what give pure water its pale blue hue. When water molecules vibrate, adjacent molecules tug and push against their hydrogen-bonded neighbors. This action absorbs a small amount of red light, leaving proportionally more blue light to scatter back to our eyes.

18. The _____ of water allows individual water molecules to stick together. a. heat capacity b. adhesion c. density d. hydrogen bonding e. latent heat of fusion

ANSWER: d NOTES: Hydrogen bonds greatly influence the properties of water by allowing individual water molecules to stick to each other.

22. What allows ice to float? a. Surface tension of ice is lower than the surface tension of liquid water. b. Adhesion of ice is lower than the adhesion of liquid water. c. Cohesion of ice is lower than the cohesion of liquid water. d. Density of ice is lower than the density of liquid water. e. Heat capacity of ice is lower than the heat capacity of liquid water.

ANSWER: d NOTES: Ice floats because the density of ice is lower than the density of liquid water.

30. Which statement is true of the relationship between latitude and ocean characteristics? a. The temperature in temperate waters is considered to be the least variable. b. Tropical waters are the only regions in which evaporation exceeds precipitation. c. Polar waters have the least variation in air temperature. d. Salinity in tropical waters varies due to high precipitati e. Precipitation exceeds evaporation in temperate waters.

ANSWER: d NOTES: Salinities are high, but vary slightly in tropical waters due to heavy rainfall that "freshens" the ocean near the equator.

26. Which describes water's latent heat of vaporization? a. The amount of energy needed to vaporize water; however, hydrogen bonds are not broken. b. The amount of energy needed to break some of water's hydrogen bonds. c. The amount of energy needed to thaw frozen ice. d. The amount of energy needed to break all of water's hydrogen bonds. e. The amount of energy needed to freeze ice.

ANSWER: d NOTES: The latent heat of vaporization is the amount of energy required to break hydrogen bonds. Only a small percentage of hydrogen bonds are broken when ice melts, but all of them must be broken during evaporation. Breaking these bonds requires additional energy in proportion to their number.

33. Which oceanic region is known for deep-water upwelling and high levels of biological productivity due to turbulence and weak stratification? a. The tropical ocean b. The Northern Atlantic ocean c. The temperate ocean d. The southern polar ocean e. The northern polar ocean

ANSWER: d NOTES: The southern polar ocean is only weakly stratified. The cold temperature of southern ocean surface water closely matches that of deep water, so no thermocline divides surface water from deep water. The absence of confining continental margins and mixing at the boundaries of the Antarctic Circumpolar Current minimize salinity differences. Turbulence and weak stratification encourage a huge volume of deep-water upwelling, which contributes to high surface nutrient levels and high biological productivity.

29. Why does the ocean not boil or freeze solid in certain regions of the world? a. Water has a low latent heat of vaporization. b. The heat capacity of solid ice is twice that of liquid water. c. Heat is transported by oceanic and atmospheric circulation. d. The ocean's thermal inertia is much lower than the land's. e. The annual freeze

thaw cycle of sea ice regulates the cycle./ ANSWER: c NOTES: Currents in the atmosphere and ocean are moving huge amounts of heat from the tropics toward the poles. Water's high heat capacity makes it an ideal fluid to equalize the polar-tropical heat imbalance. Ocean currents and atmospheric weather result from the response of water and air to unequal solar heating. Ocean currents carry heat from the tropics (where incoming energy exceeds outgoing) to the polar regions (where outgoing energy exceeds incoming).

16. Carbon dioxide is an example of a(n) ____. a. element b. atom c. compound d. polar molecule e. Proton

ANSWER: c NOTES: Carbon dioxide (CO2) is a compound - a substance that contains two or more different elements in a fixed proportion.

44. Why is the SOFAR layer efficient for sound travel? a. Refraction causes the sound energy to remain within the layer. b. The density of the SOFAR layer traps the sound energy. c. Sound energy bends away from layers of lower sound velocity. d. Temperatures and salinity conditions are homogeneous. e. Sound travels rapidly in this layer.

ANSWER: a NOTES: Although its speed is relatively slow, the transmission of sound in this minimum-velocity layer is very efficient because refraction tends to cause sound energy to remain within the layer. The outer edges of sound waves escaping from this layer will enter water in which the speed of sound is higher. This will cause the wave to speed up but then pivot back into the minimum-velocity layer. Upward-traveling sound waves that are generated within the minimum-velocity layer will tend to be refracted downward, and downward-traveling sound waves will tend to be refracted upward. In short, sound waves bend toward layers of lower sound velocity and so tend to stay within the zone.

37. The refractive index of seawater ____. a. is greater than freshwater b. is less than freshwater c. is equal to freshwater d. decreases with increasing salinity e. occurs at a 90° angle

ANSWER: a NOTES: The degree to which light is refracted from one medium to another is expressed as a ratio called the refractive index. The higher the refractive index, the greater the bending of waves between media. The refractive index of water increases with increasing salinity.

32. Which water mass is characterized by relatively constant temperature and salinity with depth? a. surface zone b. deep zone c. pycnocline zone d. halocline e. Thermocline

ANSWER: a NOTES: The surface zone, or mixed layer, is the upper layer of ocean. Temperature and salinity are relatively constant with depth in the surface zone because of the action of waves and currents.

38. What visible light frequency is almost completely absorbed and converted to heat within the first few meters of the ocean? a. red light waves b. yellow light waves c. green light waves d. blue light waves e. violet light waves

ANSWER: a NOTES: The top meter (3.3 feet) of the ocean absorbs nearly all the infrared radiation that reaches the ocean surface, significantly contributing to surface warming. The top meter also absorbs 71% of red light. Nearly all red light is converted to heat in the first few meters of ocean water, red objects a short distance beneath the surface look gray. If you were a diver working at a depth of 10 meters and you cut your hand, you would see gray blood rather than red, because there is not enough red light at that depth to reflect from blood's red pigment and stimulate your eye.

21. What property of water is responsible for the amount of time it takes for water to boil? a. adhesion b. heat capacity c. surface tension d. cohesion e. density

ANSWER: b NOTES: Because of the great strength and large number of hydrogen bonds between water molecules, more heat energy must be added to speed up molecular movement and raise water's temperature than would be necessary in a substance held together by weaker bonds. Liquid water's heat capacity is therefore among the highest of all known substances. This means that water can absorb (or release) large amounts of heat while changing relatively little in temperature.

27. Why does seawater evaporate more slowly than freshwater? a. The latent heat of evaporation is higher for seawater than freshwater. b. The dissolved salts attract and hold water molecules. c. The latent heat of evaporation is higher for freshwater than seawater. d. Salts are evaporating along with the water. e. The latent heat of vaporization is higher for seawater than freshwater.

ANSWER: b NOTES: Seawater evaporates more slowly than freshwater under identical circumstances because the dissolved salts tend to attract and hold water molecules. The latent heat of evaporation, however, is essentially the same for both freshwater and seawater. Salts are left behind as seawater evaporates.

45. Why does sound travel rapidly though the lower well-mixed surface layer? a. Temperature and pressure are homogeneous. b. Temperature and salinity are homogeneous. c. High refraction areas are produced. d. Density is heterogeneous. e. Shadow zones are produced.

ANSWER: b NOTES: Sound travels slowly in the SOFAR layer, but it moves rapidly near the bottom of the well-mixed surface layer. Temperature and salinity conditions are homogeneous there, so they do not produce any refraction.

39. How does the absorption of light provide heat energy in the ocean? a. The addition of light increases the heat capacity of molecules. b. When light is absorbed, molecules vibrate and electromagnetic energy is converted to heat. c. Photosynthetic organisms convert the light to heat energy. d. Tiny suspended particles absorb heat and transfer it to the ocean. e. The scattering of light causes heat to build up.

ANSWER: b NOTES: The absorption of light is governed by the structure of the water molecules it happens to strike. When light is absorbed, molecules vibrate and the light's electromagnetic energy is converted to heat.

34. What is the name for the density zone in which temperature changes rapidly with depth? a. pycnocline b. thermocline c. halocline d. mixed layer e. deep zone

ANSWER: b NOTES: The middle layer, the zone in which temperature changes rapidly with depth, is called the thermocline.

40. What is the typical depth of light penetration in the open ocean? a. 40 meters b. 100 meters c. 330 meters d. 600 meters e. 800 meters

ANSWER: b NOTES: The photic zone is the thin film of lighted water at the top of the surface zone. In the very clearest tropical waters, the photic zone may extend to a depth of 600 meters, but a more typical value for the open ocean is 100 meters.

31. What is the main reason for the stratification in the northern polar waters? a. temperature b. salinity c. depth d. pressure e. Precipitation

ANSWER: b NOTES: Vertical movement of water in the northern polar ocean is limited. The stratification is caused largely by a salinity difference between surface water and water at great depths.

28. What is thermal inertia? a. The increase of heat energy b. The propensity for a substance to resist temperature changes c. The amount of heat needed to vaporize water d. The amount of heat energy needed to raise the temperature of one gram of a substance by 1° Celsius e. The amount of heat needed to break all hydrogen bonds

ANSWER: b NOTES: Water temperature rises as the sun's energy is absorbed and changed to heat, but water has a very high heat capacity, so its temperature will not rise very much even if a large quantity of heat is added. This tendency of a substance to resist a change in temperature with the gain or loss of heat energy is called thermal inertia.