Chapter 09 - Water: A Physically Unique Molecule

9-1

Chapter 9

Unit 3 – Chapter 9

Water: A Physically Unique Molecule

NATIONAL SCIENCE EdUCATION CONTENT STANdARdSReference:

National Research Council, (1999). National Science Education Standards. National Academy Press, Washington, DC.

Charted here are the science education content standards covered in Chapter 9, Water: A Physically Unique Molecule. As a result of activities provided for high school science students in this part of the curriculum, the content of the standard identified below by a check (4) is to be understood or the abilities are to be developed by the student.

CHAPTER 9 NATIONAL SCIENCE EdUCATION CONTENT STANdARdS, GRAdES 9-12

Unifying Concepts And Processes

Science as Inquiry Physical Science Life Science

4 Systems, order, and organization

4 Abilities necessary to do scientific inquiry

4 Structure of atoms 4 The cell

4 Evidence, models, and explanation

4 Understandings about scientific inquiry

Structure and properties of matter

Molecular basis of heredity

4 Change, constancy, and measurement

Chemical reactions Biological evolution

4 Evolution and equilibrium

Motions and forces Interdependence of organisms

4 Form and function 4 Conservation of energy and increase in disorder

Matter, energy, and organization in living systems

Interactions of energy and matter

Behavior of organisms

Earth and Space Science

Science and TechnologyScience in Personal and

Social PerspectivesHistory and Nature

of Science

4 Energy in the Earth system

Abilities of technological design

Personal and community health

4 Science as a human endeavor

Geochemical cycles 4 Understandings about science and technology

Population growth Nature of scientific knowledge

Origin and evolution of the Earth system

Natural resources Historical perspectives

Origin and evolution of the universe

Environmental quality

4 Natural and human induced hazards

Science and technology in local, national, and global challenges


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Unit 3

Life on an Ocean Planet Teacher Curriculum Guide

OCEAN LITERACy – ESSENTIAL PRINCIPLES ANd FUNdAMENTAL CONCEPTSReference: www.coexploration.org/oceanliteracy.

Charted here are the Ocean Literacy: Essential Principles and Fundamental Concepts introduced or covered in Chapter 9, Life on an Ocean Planet. Those principles and fundamental concepts checked (4) below should be understood by the student.

For complete text of all the Fundamental Concepts under each Principle, see Section Two of this guide.

CHAPTER 9 CORRELATION TO OCEAN LITERACy: ESSENTIAL PRINCIPLES ANd FUNdAMENTAL CONCEPTS

Principle 1 Principle 2 Principle 3 Principle 4 Principle 5 Principle 6 Principle 7

The Earth has one big ocean with many features.

The ocean and life in the ocean shape the features of the Earth.

The ocean is a major influence on weather and climate.

The ocean makes Earth habitable.

The ocean supports a great diversity of life and ecosystems.

The ocean and humans are inextricably interconnected.

The ocean is largely unexplored.

Fundamental Concepts







A

B

C

D

4 E

4 F

G

H

A

B

C

D

E

4 A

4 B

C

D

4 E

4 F

G

A

B

4 A

4 B

C

D

4 E

4 F

G

H

I

A

B

C

D

E

F

G

A

B

C

D

E

F

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Chapter 9



CHAPTER SCOPE ANd SEQUENCING

CHAPTER SCOPE ANd SEQUENCE FOR PLANNING WATER: A PHySICALLy UNIQUE MOLECULE

Activity Topic Time Element

I. The Physics of Water 2.6 hoursLecture A. Heat and Heat Capacity 15 minutes

Lecture B. Water Temperature and Density 20 minutes

Lecture C. Latent Heat of Vaporization 20 minutes

Lecture D. Thermal Inertia 20 minutes

Lecture E. Ocean Water Density 20 minutes

Laboratory/Activity #1 It’s Just Going Through One of Those Phases 60 minutes

II. How Water Physics Affect Marine Life 3.5 hoursLecture A. Light 20 minutes

Lecture B. Temperature 20 minutes

Lecture C. Sound 20 minutes

Lecture D. Pressure 20 minutes

Lecture E. Size and Volume 20 minutes

Lecture F. Buoyancy 20 minutes

Lecture G. Movement and Drag 15 minutes

Lecture H. Currents 15 minutes

Laboratory/Activity #2A Touch of Blue – A Series of Studies of Light, Sounds, and Pressure in the Sea

60 minutes

FEEdbACkCompare Pre/Post-concept Maps1. Compare Pre/Post-test Results2. Student Tutorial (if necessary)3.

CHAPTER 9 FLOW CHART

bEGIN HEREMotivate•

Questions 4

discussions 4

demonstrations 4

Vocabulary/Morphemes•Expectations/Conduct•Pre-assessment•

Pre-concept Map 4

Pre-test 4

REFLECTIONEnrichment Experience•

Elaborate 4

Extension 4

EVALUATIONAssessment Strategies•Post-assessment•

Conceptual Change 4

Post-concept Map 4

Post-test 4

Lab Activity #2 A Touch of

blue—A Series of Studies of Light,

Sounds, and Pressure in the

Sea

Lab Activity #1

It’s Just Going Through One of Those Phases

The Physics

of Water

How Water Physics Affect Marine Life


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Unit 3


LEARNING OUTCOMESWhat is • heat? What is temperature? How do they differ?

What are the two common •systems used to measure temperature? Which one is most used by scientists?

What is • heat capacity? How do you measure it?

What implications does heat •capacity have on Earth’s climate?

What unique characteristics does •water exhibit as it turns from vapor to liquid to ice?

What is • latent heat of fusion? What is the difference between sensible and non-sensible heat?

What is• latent heat of vaporization?

What are • thermal inertia and thermal equilibrium? Why are these concepts important to life and Earth’s climate?

What are the relationships •between the salinity, temperature, and density of seawater?

How and why is the ocean •stratified by density?

What are the three density layers •of the ocean? Approximately what proportion of the ocean does each layer account for?

What is a • thermocline?

How does water scatter and •absorb light?

What are the • photic, euphotic, dysphotic, and aphotic zones?

What advantage does ocean-•based existence have over land-based existence with respect to temperature?

What are an • ectotherm, an endotherm, a homeotherm and a poikilotherm?

How does temperature •affect metabolism? What’s the advantage of being an endotherm?

(Continued on next page)

MOTIVATIONAL STRATEGIESThe following motivational strategies are included as suggestions for creating interest and curiosity, for providing relevance of the content, for making connections between past and present learning experiences, and for providing context for the lessons.

Questions to Elicit Prior Student knowledgeTo engage students and assess students’ prior knowledge of the overall chapter content and to guide their learning, you may want to ask these questions before launching into each core chapter topic.

QUESTIONS TO ELICIT PRIOR STUdENT kNOWLEdGE

Topic Question

The Physics of Water

What property is the most crucial in explaining the physics of water?

How Water Physics Affect Marine Life

How do physical properties of sea water affect marine organisms?

Marine Career discussionIn this chapter students learn some of the basic science concepts that a marine biologist would need to know to study bioluminescent organisms in the ocean. Edith A. Widder is a marine biologist who has been very successful at combining the disciplines of biochemistry, neurobiology, mathematics, and engineering to study one of the most important processes in the ocean – bioluminescence.

As students study this chapter, ask them to think about the importance of bioluminescence for life in the deep sea.

Mind Capture demonstrationThese teacher demonstrations may be used to introduce this chapter or different parts of the chapter, or may be used as a team inquiry- based activity.


1. Heat Capacity of the Land versus the Sea

Inquiry:

Ask students if they have been to the beach during a summer day and night. Ask them what they have observed about differences between the temperature of the beach and the water.

Objective:

This “Mind Capture” demonstration or inquiry will provide evidence for the higher heat capacity of water compared to sand or land.

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How does water affect sound? •How do some marine mammals use sound in water to their advantage?

What is • hydrostatic pressure?. What effects does it have on marine life?

How do surface-to-volume ratios •change as cell size increases?

Why is a high surface-tovolume •ratio important to cell function?

How does buoyancy affect both •swimming and drifting marine organisms?

What characteristics allow marine •organisms to avoid sinking? What characteristics do marine organisms have to handle water resistance?

How does water movement affect •the distribution and survival of marine life?

Materials:

Clock or watch with second hand•Heat lamp•Sand •Tap water •Two thermometers•Two 500 mL beakers•

Procedure:

1. Place 200 mL of water into one of the beakers.2. Place 200 g of sand in the other beaker.3. Position a thermometer in each beaker. The thermometer can rest

on the bottom of the beaker.4. Place the lamp about 20 centimeters above the beakers. Make sure

that each beaker receives the same amount of light.5. Heat the two beakers for 20 minutes. You may have students record

the temperature for both the water and the sand each minute.6. After 15 minutes, turn off the lamp and remove it from the area

so that the water and sand in the two beakers can cool.7. You may have students record the temperature for the water and

the sand each minute for 20 minutes.

8. Students may construct a graph of their data.

Results:

The water heats more slowly than the sand. The water also cools more slowly than the sand.

Conclude and Communicate:

Water has a high heat capacity and therefore the temperature of the water does not rise as quickly as that of the sand. This property explains land and sea breezes, which students will learn about in Chapter 11. As the temperature of the sand rises during the day, the air above the sand is warmed and it begins to rise leaving behind an area of low pressure. The cooler, higher pressure air over the sea moves toward land creating a sea breeze.

The temperature of the water also does not decrease as quickly as that of the sand. At night, this is explains why the sea feels warmer than the sand on a nearby beach. The air above the sea at night will be warmer than that above the land and it will rise, leaving a lower pressure area over the sea. This creates the opposite flow of air from the land – a land breeze.

A high heat capacity also explains why the ocean is warmer in the later months of the summer than in the early months of the summer. More intense hurricanes occur during the later months of the summer also. Students will learn more about this phenomena in Chapter 11, but understanding heat capacity is an important basic thermal property of water.

The high heat capacity of water allows ocean water to store large amounts of heat energy without causing much temperature change. Coastal locations have milder climates than inland locations because of the high heat capacity of water.

LEARNING OUTCOMES (CONTINUEd)


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Unit 3


2. The Egg and the Bottle

Inquiry:

Ask students how air pressure could be used to get the hard-boiled egg to go into a bottle with a slightly smaller opening (without breaking the egg open).

Objective:

This “Mind Capture” demonstration shows students how temperature affects air pressure. This demonstration may also be used as a motivational strategy for Chapter 11.

Materials:

Hard boiled egg without the shell•Bottle with an opening slightly smaller than the egg•Match•Small strip of newspaper•

Procedure:

1. Light a small piece of newspaper and drop it into the bottle.

2. Quickly place the egg over the opening to the bottle. If the flame goes out too soon, you may need to repeat these two steps.

3. Have students observe the egg going into the bottle.

4. Once the egg is in the bottle, ask students for suggestions for getting the egg out of the bottle without breaking it.

5. To get the egg out of the bottle, tilt the bottle downward with the smaller end of the egg in the opening of the bottle.

6. Blow fairly hard into the bottle opening. Use your hand to make a seal between your mouth and the neck of the bottle. As soon as the egg begins to come out, move the bottle away from your mouth.

Results:

The egg should shake a little and then go into the bottle. The egg should come out as you blow into the bottle.


When the lighted newspaper was placed in the bottle the air was heated and it expanded. Some of the air escaped causing the egg to shake. Rising warm air leaves behind an area of low pressure in the bottle. The egg then blocked the opening and the higher pressure air on the outside of the bottle pushes the egg into the bottle. When you blow into the bottle, the air pressure becomes higher on the inside of the bottle, pushing the egg back out of the bottle.

VOCAbULARy

absolute pressure (p. 9-26)•

aphotic zone (p. 9-19)•

Archimedes’ Principle (p. 9-29)•

atmospheric pressure (p. 9-25)•

bar (p. 9-25)•

buoyancy (p. 9-29)•

calorie (p. 9-5)•

chromatophores (p. 9-20)•

countershading (p. 9-20)•

drag (p. 9-31)•

dysphotic zone (p. 9-19)•

echolocation (p. 9-23)•

ectotherm (p. 9-21)•

endotherm (p. 9-21)•

equalizing (p. 9-26)•

euphotic zone (p. 9-19)•

gauge pressure (p. 9-26)•

heat (p. 9-4)•

heat capacity (p. 9-6)•

homeotherm (p. 9-21)•

hydrostatic pressure (p. 9-25)•

joule (p. 9-5)•

latent (p. 9-8)•

latent heat of fusion (p. 9-8)•

latent heat of vaporization •(p. 9-10)

metabolism (p. 9-21)•

non-sensible heat (p. 9-7)•

photic zone (p. 9-16)•

poikilotherm (p. 9-21)•

sensible heat (p. 9-7)•

state (p. 9-7)•

streamlining (p. 9-32)•

temperature (p. 9-4)•

thermal equilibrium (p. 9-11)•

thermal inertia (p. 9-11)•

thermocline (p. 9-14)•

transpiration (p. 9-10)•

turbulence (p. 9-32 )•

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Chapter 9



3. The Floating Egg

Inquiry:

Ask students whether an object floats better in salt water or fresh water? What effect does the density of the water have on the buoyancy of an object?

Objective:

This “Mind Capture” demonstrates the difference between the density of freshwater and saltwater and the effect on buoyancy of an object, such as an egg.

Materials:

Hard boiled egg•Beaker•Salt•Tap water•

Procedure:

1. Put 200 mL of fresh water in each of two beakers. In one of the beakers, add approximately 5 tablespoons of salt. Kosher salt will dissolve best and leave the water clear. Have students make a prediction as to whether the egg will float.

2. Gently place a hard boiled egg in the fresh water.

3. Remove the egg.

4. Have the students predict whether the egg will float in the saltwater. Place the egg in the salt water.

Results:

The egg will not float in the freshwater, but will float in the saltwater.


Ask students when an object floats?

An object floats when its density is less than the density of the water around it. An object with a density greater than that of water will sink. Density is defined as the amount of particles (mass) within a certain space (volume).

Adding certain materials to water, such as salt, can increase its density. If salt is added to fresh water, the amount of matter within the space the water occupies is increased, since salt molecules are crowded into the same space as the water. This makes salt water denser than fresh water.

MORPHEMESa – not, without•

baros – heavy•

bio – living•

chroma – color•

dys – difficult•

ektos – outside•

endon – within•

eu – good, well•

halo – salt•

homos – same•

hydro – water•

latent – to lie hidden•

luci – light•

photo – light•

plankton – wandering•

pycno – dense•

therme – heat•

sali – salt•

statis – standing still•

steno – narrow or small•

eury – wide or broad•


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Unit 3


4. Soda and Density Differences

Inquiry:

This “Mind Capture” demonstrates the difference between the density of a diet and a regular soda when placed in tap water.

Objective:

This “Mind Capture” demonstration shows students how objects of different densities float or sink.

Materials:

Tap water•1 can of diet soda •1 can of regular soda•Large clear container•

Procedure:

1. Ask students to make a prediction as to whether the cans of soda will float.

2. Place a diet soda and regular soda in two different containers filled with tap water.

Results:

The regular soda will sink and the diet soda will float.


The sugar causes the regular soda to be denser and it sinks. You may also place the regular soda in saltwater to show the students that it will float higher than in the fresh water.

5. Who Shrunk the Cup?

Inquiry:

This “Mind Capture” demonstration shows the effect of water pressure on objects with air spaces.

Objective:

This demonstration can be used to differentiate between an observation and an inference and to show students the effect of water pressure on an object taken to great depths.

Materials:

Styrofoam cup•Small styrofoam cup from a deep sea dive •

Procedure:

1. Ask students to make some observations about each of the two styrofoam cups.

2. Ask students to make some inferences about how the one cup became small.

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Chapter 9



Results:

The smaller cup was taken down into the ocean to a depth of at least 1,000 feet. The styrofoam cups are generally placed in a sack-like container and attached to the outside of the submersible. The water pressure caused the cup to become smaller. Styrofoam cups keep their general shape because air is even spaced through the material.


An observation is a statement about information that is available directly through the senses and an inference is an interpretation of these observations. To infer, you use preexisting experiences and knowledge to fill in gaps between observations and information.

EXPECTATIONS / STUdENT CONdUCTStudents may be involved in guided discussion as the teacher •explains the content of the chapter through a teacher-led presentation. Students will be expected to respond to questions, ask questions, takes notes, draw and label diagrams.Students may study the chapter individually as they read and •respond to questions.Students may work in collaborative teams as they conduct inquiry-•based activities and work on specific enrichment experiences and assessments.Students should start each chapter by familiarizing themselves with •the chapter vocabulary and morphemes list. Students may develop a chapter concept map using the vocabulary list. This initial concept map can be compared with a summative concept map to determine what learning has taken place and whether misconceptions remain.


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Unit 3


TEACHING CHAPTER 9

Instructional Strategy – Teacher Led Presentation Exploration Through discussion

WATER: A PHySICALLy UNIQUE MOLECULE

I. The Physics of Water

By the end of this section, students will be able to answer these questions:1. What is heat? What is temperature? How do they differ?

2. What are the two common systems used to measure temperature? Which one is most used by scientists?

3. What is heat capacity? How do you measure it?

4. What implications does heat capacity have on Earth’s climate?

5. What unique characteristics does water exhibit as it turns from vapor to liquid to ice?

6. What is latent heat of fusion? What is the difference between sensible and non-sensible heat?

7. What is latent heat of vaporization?

8. What are thermal inertia and thermal equilibrium? Why are these concepts important to life and Earth’s climate?

9. What are the relationships between the salinity, temperature, and density of seawater?

10. How and why is the ocean stratified by density?

11. What are the three density layers of the ocean? Approximately what proportion of the ocean does each layer account for?

12. What is a thermocline?

1. Water’s physical properties not only affect the life processes of marine organisms, but of human beings in the water.

a. These effects are not only important for understanding marine life, but for marine scientists and others who enter the underwater world as scuba divers.

A. Heat and Heat Capacity1. Temperature is crucial in determining where organisms can

live in the ocean.

a. Many aquatic organisms can only live in the narrow temperature range to which they are adapted. Therefore, a temperature increase of only a few degrees can kill fish and other organisms in the environment.

2. The concept of temperature comes from the need to measure the relative heat of two bodies, or the same body after

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removing or adding heat.

a. In the case of two bodies at different temperatures, heat flows from the hot to the cold body until their temperatures become equal. This is called entropy—the flow of energy from an area of high concentration to an area of low concentration.

b. However, it’s important to realize that heat and temperature, while interrelated, are two different concepts.

3. Suppose you’ve filled a bathtub with warm water and scooped out a glassful. If you take the temperatures of the water in the glass and the water in the tub, you’ll find they are the same. But, which has more heat?

a. Drop an ice cube in the glass and another one in the tub, let them melt, and take the temperatures again. You would find the ice made the temperature in the glass substantially lower, whereas it didn’t cool the tub water enough to make a measurable difference.

What is heat? What is temperature? How do they differ?4. This highlights the difference between heat and temperature.

a. Heat is the kinetic energy in the random movement, or vibration, of individual atoms and molecules in a substance. The faster the molecules move the more heat the substance has.

b. The total heat energy is measured based on both the quantity and speed of vibrating molecules.

c. Temperature measures the degree of molecular vibration only.

5. The glass and tub of water both had the same temperature, but the tub had far more heat because it contained many times more moving molecules.

a. The ice cube made little difference to the tub’s temperature because the heat change was insignificant among the large number of molecules.

b. But, the glass of water had many fewer molecules, so the ice made it much colder.

6. Suppose you wanted to raise the temperature of the water in the tub and the glass to the same degree.

a. Using a given heat source, which would you have to heat longer, the glass or the tub?

b. The tub, of course, because there are many more molecules that must vibrate faster.

What are the two common systems used to measure temperature? Which one is most used by scientists?

7. Although temperature measures only the degree of molecular motion, it’s one of the most basic measurements in studying marine science.

a. Temperature differences influence how quickly heat travels


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Unit 3


from one substance to another, and therefore affect weather, climate, and marine life.

b. As you’re probably aware, the two most common temperature systems are fahrenheit (F) and celsius (C).

c. Fahrenheit is used in the United States and a few other countries, whereas celsius is used in countries that use the metric system.

d. Celsius is the scale most used in science because it is based on water’s physical properties: 0°C is the freezing point of water, and 100°C is its boiling point.

What is heat capacity? How do you measure it?8. To measure the actual amount of energy—not just how quickly

the molecules vibrate—you use calories.

a. A calorie is the amount of energy needed to raise 1 gram of water 1 degree Celsius. It takes more energy—more calories—to raise a tub of water a given number of degrees than to raise a glass of water the same number of degrees.

b. (Note: The term calorie as listed for the energy content in food items differs from calories as discussed here. The nutritional calorie is actually a “giant” calorie or kilocalorie—1,000 calories.)

c. Also note that scientists also measure energy in joules. 4.2 joules= 1 calorie.

9. This leads us to heat capacity: the amount of heat energy required to raise a given amount of a substance by a given temperature.

a. Heat capacity is measured in calories per gram.

b. The value for water is 1.00 calorie per gram. This is because calories are defined based on the heat capacity of pure water. Substances have varying heat capacities, mostly lower than 1 calorie per gram.

10. Water has a very high heat capacity. Chapter 8 explains that water’s hydrogen bonds hold water molecules together, which is why water is liquid rather than vapor at room temperature.

a. Because hydrogen bonds hold water molecules together, water resists molecular motion. This means it takes more heat energy to raise water’s temperature than that of most other substances.

b. Therefore, water can absorb or release a lot of heat with little temperature change.

What implications does heat capacity have on Earth’s climate?11. This is more than an interesting fact. Water’s heat capacity

affects you and everyone on Earth every day.

a. It influenced what you wore to school today, because it influences the world’s climate and weather.

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b. Among other things, it does this by carrying heat to areas that would otherwise be cooler, and by absorbing heat in areas that would otherwise be hotter.

12. A great example is the island of Bermuda. Bermuda has a moderately tropical climate year round, even though it lies above 30° north latitude. That’s about the same latitude as Birmingham, Alabama, or Fort Worth, Texas, both of which experience some snow and freezing rain in the winter.

a. The difference is that the warm Gulf Stream current flows around Bermuda. The tremendous heat capacity of water offsets the normally moderate temperature of this latitude.

b. By carrying so much heat north, the Gulf Stream gives Bermuda a tropical climate.

B. Water Temperature and Density

What unique characteristics does water exhibit as it turns from vapor to liquid to ice?

1. Chapter 8 explains that water is unusual because it becomes less dense as it freezes. Most substances become denser as they cool and less dense as they warm.

2. The maximum density of pure water is approximately 1 gram per cubic centimeter (1g/cm3 or 62.4 pounds per cubic foot).

a. Water becomes denser as it cools, but only to a point. At 3.98°C (39.16°F), it reaches maximum density.

b. As water cools below the point of maximum density, it begins to crystallize into ice. As it moves into a solid state (state is an expression of a substance’s form, which changes from solid, to liquid, to gas with the addition of heat), it becomes less dense.

c. At 0°C, pure water freezes and the density drops abruptly. This is because the crystal structure of the water molecules changes the bond angle between the oxygen and hydrogen atoms from 105° to 109°.

d. The crystal structure forms a hexagon (structure with six sides) that acts like a raft because it increases the space the molecules take up by 9%.

e. This space increase is why the density decreases. Note that salt water freezes at slightly below 0°C.

3. Ice becomes denser as the temperature drops below 0°C, but the density never rises above that of liquid water.

a. The density of ice is approximately 0.917 grams per cubic centimeter (0.917g/cm3 or 57.2 pounds per cubic foot).

b. This is less than the density of liquid water, which is why ice floats. It’s also why ice forms on top of the water—freezing over—whereas most liquids turn solid from the bottom up.

c. Also, ice doesn’t form all at once at its freezing point (0°C), but crystallizes continuously until all the liquid turns solid.


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The temperature does not drop any further until all the liquid water freezes, even though heat continues to leave.

Guided discussion question(s): What is the connection between the properties of ice and the thermal conditions on Earth? Because water expands and floats when it freezes, ice can absorb the morning warmth of the sun, melt, then re-freeze at night giving back to the atmosphere the heat it stored through the daylight hours. The heat content of the water changes through the day; its temperature does not. Without these properties of ice, temperatures on the Earth’s surface would change dramatically.

What is latent heat of fusion? What is the difference between sensible and non-sensible heat?

4. This produces the phenomenon of non-sensible heat.

a. As water cools, you can read the temperature drop with a thermometer— this is sensible heat (i.e., heat that you can sense with a thermometer).

b. If 1 gram of liquid water loses 1 calorie of heat, the temperature will drop 1°C. Once water cools to 0°C, however, 1 gram must lose 80 calories to form ice, and the temperature does not change while that heat diminishes.

c. This is called non-sensible heat because there’s a change in heat energy, but you can’t sense it with a thermometer.

5. The non-sensible heat lost when water goes from liquid to solid state is called the latent heat of fusion. On the graph of water’s temperature and density, the abrupt density drop at 0°C represents it.

6. Latent heat of fusion also comes into play when ice melts back into water.

a. The 80 calories per gram required to freeze all the water into ice must go back into the ice to turn all of it back into liquid water.

b. Just as the ice doesn’t change temperature until all the water freezes, when melting, ice doesn’t change temperature until all of it turns into liquid. This is why ice cubes cool beverages so effectively.

C. Latent Heat of Vaporization

Reference the National Science Teachers Association (NSTA) SciLinks Service

Topic: Latent Heat

Go To: www.scilinks.org

Code: LOP21751. Hydrogen bonds give water its high heat capacity and make it

resist evaporation.

INTE

RNET

PORTAL

http://www.scilinks.org/fromoutside.asp?sciLINKSNumber=LOP2175


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a. When you apply enough heat energy, however, individual water molecules begin to vibrate with enough force that hydrogen bonds cannot hold together.

b. The molecules evaporate by diffusing into the air. This process begins at 100°C (212°F) at sea level.

(Note that pressure affects the temperature at which water evaporates).

2. Just as ice doesn’t become any cooler until it all freezes, water does not get any warmer until it all vaporizes (changes its state from a liquid to a vapor).

a. A good example is when you cook something in boiling water. Although you continue to heat the boiling water, the temperature doesn’t change, which is why boiling provides an even cooking temperature.

What is latent heat of vaporization?


Topic: Phases of Matter


Code: LOP2185

3. The heat required to vaporize a substance is called latent heat of vaporization.

a. At 540 calories per gram, water has the highest latent heat of vaporization of any known substance.

b. It takes much more latent heat to vaporize water than to freeze it (540 calories per gram versus 80) because when water freezes only some of the hydrogen bonds break. When it vaporizes, all the hydrogen bonds must break, which requires more energy.

4. Evaporation is another way that water affects you every day.

a. Annually, enough water evaporates from the ocean to reduce the depth by a meter—334,000 cubic kilometers (about 80,000 cubic miles) of water.

b. The energy for evaporation comes from the sun’s heat, which causes water to change from liquid to vapor.

c. Eventually water vapor in the atmosphere condenses into liquid water (rain) and releases the heat energy into the atmosphere.

d. Condensation is a major source of energy for the atmosphere: it powers storms, winds, wind waves, and ocean currents. The rain and runoff replace the evaporated water in the hydrological cycle, so the sea level doesn’t drop.

INTE

RNET

PORTAL




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Unit 3


D. Thermal Inertia


Topic: Water Cycle


Code: LOP2180

What are thermal inertia and thermal equilibrium? Why are these concepts important to life and Earth’s climate?

1. Water’s high heat capacity provides the Earth with thermal inertia, which is the tendency to resist temperature changes.

a. Because of its high heat capacity, seawater temperature doesn’t rise or fall much, even when gaining or losing large quantities of heat.

b. Therefore, temperature changes in the sea tend to be much less severe and more gradual over time.

c. By comparison, temperatures on land may vary widely—20°C/68°F in a single day in some climates at some times of the year.

2. However, thermal inertia is important to organisms on land as well as in the sea because the Earth receives a tremendous amount of energy from the sun—10,000 times the amount of energy consumed by humans.

a. About half of this energy makes it through the atmosphere, much of it being absorbed by the ocean.

b. Through convection, evaporation, and radiation, the heat returns to the atmosphere and radiates back into space.

c. Over time, the incoming solar radiation and Earth’s internal heat sources balance with the outward radiating heat.

d. This keeps the Earth in thermal equilibrium, meaning that it cools at about the same rate that it heats. Over time, it grows neither significantly warmer nor colder.

3. Daily and seasonally, seawater acts as a global thermostat, preventing broad temperature swings caused by uneven solar heating across the globe.

a. Seawater absorbs heat during the day and during the summer and then releases it back into the atmosphere at night and during the winter.

b. Also, sea ice found in the polar regions absorbs heat as it melts during the day and releases heat as it refreezes in the night.

c. The temperature differences between day and night or winter and summer would be much greater without the ocean providing thermal equilibrium.

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d. Without the thermal inertia provided by water, many—perhaps most—of the organisms on Earth could not survive the drastic temperature changes that would occur every night.

4. Every species has a range of conditions in which it can live and beyond which it can’t.

a. These conditions include temperature, salinity, and light intensity, among many others.

b. Some species can tolerate a wide variety of environmental conditions and so can live in a large number of places.

c. Others can tolerate only a narrow range of conditions and are more restricted in where they can live.

d. An organism may have a wide range of tolerance for one condition (e.g., temperature) and a narrow range for another (e.g., salinity).

5. Tolerance ranges tend to affect each other. For example, sea stars can tolerate a wide range of temperatures, but if they are living near their temperature limit, they are under stress and are less tolerant of changes in other environmental factors, such as salinity.

a. An organism’s tolerance range partly defines the ecological community in which it can live.

Guided discussion question(s): Input of solar radiation in the Seattle, Washington (Northern Hemisphere) peaks in June and reaches a minimum in December because of the Earth’s orbital tilt. If this is the case, why would the warmest days occur in August and September and the coldest days in January and February? Discuss with students that because of thermal inertia, there is a lag between maximum sunlight and maximum warmth due to water’s great heat capacity. The sun must be present and shine on Earth for many weeks to raise the summer hemisphere’s temperature. Water also retains heat, so the coldest days in the winter hemisphere come well after the darkest days.


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E. Ocean Water Density


Topic: Density of Water


Code: LOP2190

What are the relationships between the salinity, temperature, and density of seawater?

1. As you’ve learned, seawater density varies with salinity and temperature.

a. Seawater density typically varies between 1.02g/cm3 and 1.03g/cm3. This means seawater weighs about 2%–3% more than pure water, which has a density of 1g/cm3.

2. Seawater density increases with increasing salinity and decreasing temperature.

a. Cold, salty water is denser than warm, fresh water.

b. Water pressure also plays a role, although a smaller one than temperature and salinity. Deep water is somewhat denser than shallow water because of the weight of the water above it.

Guided discussion question(s): Using the term density, explain how a small bag of salt water can sink in a large beaker of salt water. Where might this occur in the ocean? Encourage students to think about the temperature of the salt water in the small bag. Lower temperature leads to a more dense substance. This phenomenon occurs in the polar regions, where frigid air temperature lowers surface ocean temperatures so that surface water sinks.

How and why is the ocean stratified by density?3. Because temperature and salinity affect water density, seawater

stratifies, or forms layers.

a. Dense water is heavy and sinks below less dense layers.

b. Generally, there are three distinct layers (or zones) found in the ocean. Oceanographers usually define the zones based on temperature variations (although they could also use salinity or density).

c. They are the surface zone (mixed layer), the thermocline, and the deep zone. Defining the layers can be complex because they vary regionally, depending on the conditions that affect temperature and salinity.

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What are the three density layers of the ocean? Approximately what proportion of the ocean does each layer account for?

4. The surface zone is also called the mixed layer. Temperature and salinity are relatively constant here because waves and currents continually mix the water; although, variations do exist.

a. The surface zone is the most biologically productive because it’s exposed to sunlight, yet it accounts for only about 2% of the ocean’s volume. The surface zone extends from the surface to about 100 meters (328 feet) in most places, although it may be as deep as 500 meters (1,640 feet).

What is a thermocline?5. These relatively warm, low-density surface waters are separated

from cool, high-density deep waters by the thermocline, the zone in which temperature changes rapidly with depth.

a. The top of the thermocline varies with season, weather, currents, and other conditions.

b. It depends in part on the amount of heat the surface zone receives from the sun and is therefore more pronounced in tropical and temperate waters.

c. Thermoclines are weaker in polar regions because the surface water there is cold.

d. Thermocline zones account for about 18% of ocean water.

6. Below the thermocline is the deep layer. This layer is cold, dense, and fairly uniform because it originates in the polar regions.

a. It begins deeper than about 1,000 meters (3,280 feet) in the middle latitudes but becomes shallower until it reaches the surface in the polar regions.

b. The deep zone makes up about 80% of the ocean’s volume.

II. How Water Physics Affect Marine Life

By the end of this section, students will be able to answer these questions:1. How does water scatter and absorb light?

2. What are the photic, euphotic, dysphotic and aphotic zones?

3. What advantage does ocean-based existence have over land-based existence with respect to temperature?

4. What are an ectotherm, an endotherm, a homeotherm and a poikilotherm?

5. How does temperature affect metabolism? What’s the advantage of being an endotherm?

6. How does water affect sound? How do some marine mammals use sound in water to their advantage?


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7. What is hydrostatic pressure? What effects does it have on marine life?

8. How do surface-to-volume ratios change as cell size increases?

9. Why is a high surface-to-volume ratio important to cell function?

10. How does buoyancy affect swimming and drifting marine organisms?

11. What characteristics allow marine organisms to avoid sinking? What characteristics do marine organisms have to handle water resistance?

12. How does water movement affect the distribution and survival of marine life?

A. Light

Guided discussion question(s): Why is water blue? Lead students into a discussion regarding water scatter and light absorption.

How does water scatter and absorb light?1. Light only penetrates the upper regions of the sea—an area

called the photic zone.

a. In the clearest conditions, light cannot penetrate in significant amounts much deeper than 600 meters (1,968 feet); penetration to 100 meters (328 feet) is typical.

b. Significant light reaches no more than about 2% of the ocean because water scatters and absorbs light.

2. Scattering occurs initially when light reaches the water’s surface.

a. Most light penetrates the surface, but, depending on the sun’s angle, some may reflect back out of the water.

b. Within the water, some light reflects off light-colored suspended particles, sending some of the light back to the surface and out of the water.

c. Dark, suspended particles and algae absorb some of the light.

3. Water—even pure water with no suspended particles— also absorbs light directly.

a. As light travels through water, it strikes water molecules. The water molecules absorb the energy, converting the light into heat.

b. However, water doesn’t absorb light uniformly.

4. White light from the sun is actually the combination of all visible colors, each with a different wavelength and radiant energy.

a. Colors at the red end of the spectrum have low energy and a long wavelength; colors at the blue end have high energy and a short wavelength.

b. Water absorbs fractions of various colors as light travels through it, more easily removing the long wavelength/low energy colors.

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c. In other words, water absorbs colors at the red end of the spectrum more easily than at the blue end.

d. The first meter of water absorbs nearly all infrared (invisible to the eye) light.

e. The color red is almost totally absorbed at 4 meters (13 feet).

f. As light passes through more water, orange is almost completely absorbed next, followed by yellow, green, blue, indigo, and violet.

5. While water absorbs colors in the order listed, it’s a gradual process.

a. That is, the color red doesn’t suddenly disappear at 3 meters (10 feet). The water absorbs it gradually so very little is left at 3 meters (10 feet).

b. Even then, some of each color may continue deeper, although not necessarily in significant amounts.

6. Blue is the strongest color and must travel through the most water before it’s completely absorbed.

a. This is why very clear water (without a high plankton concentration or suspended particles) looks blue.

b. Light enters the water, scattering and reflecting in different directions. As the light travels, almost all the other colors get absorbed. Blue light remains when it reflects and emerges back from the water.

7. How deeply light penetrates depends on how clear or turbid the water is.

a. In coastal areas with lots of runoff, penetration may be limited to less than 3 meters (10 feet).

b. In the clearest water, a spectrophotometer may detect light as deep as 590 meters (1,936 feet). However, as mentioned, significant light penetration is limited to about 100 meters (328 feet).

c. Nonetheless, in ideal conditions there can be enough visible light from the surface at 150 meters (492 feet) for the human eye to see by.

What are the photic, euphotic, dysphotic and aphotic zones?8. Two zones exist with respect to light penetration: the photic

zone and the aphotic zone.

a. Although the photic zone may reach as deep as 200 meters (656 feet), the most biologically productive region is the upper, shallow portion. This subzone of the photic zone is called the euphotic zone.

b. The euphotic zone comprises only about 1% of the ocean, yet the vast majority of marine life exists there and depends on the light for survival.


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c. This is the zone where photosynthetic organisms bring light energy into the biological cycle.

d. The lower region of the photic zone is the dysphotic zone. Light reaches this region, but there’s not enough for photosynthetic life.

9. The aphotic zone is where light doesn’t reach. It actually makes up the vast majority of the ocean, though only a fraction of marine organisms live there.

B. Temperature

What advantage does ocean-based existence have over land-based existence with respect to temperature?

1. As you learned earlier, seawater doesn’t fluctuate in temperature nearly as much as air does.

a. Marine organisms rarely encounter temperatures below 1.9°C or above 30°C. Compared to land-based climates, this narrow range provides an advantage.

b. Marine organisms live in a much less challenging environment with respect to temperature range.

2. Generally, temperature dictates the rate of chemical reaction.

a. The higher the temperature, the more quickly reactions take place. This is true in biological reactions and in reactions not related to life.

b. The higher the temperature within an organism, the more quickly energy-releasing chemical processes happen. Generally, these processes (metabolism) double in rate for each 10°C increase.

c. Metabolic rate is proportional to how quickly an organism moves or reacts. For example, refrigeration is effective in preserving food because the low temperature greatly slows organisms that reproduce and decompose the food, keeping it fresh.

What are an ectotherm, an endotherm, a homeotherm and a poikilotherm?

3. Most marine organisms have an internal temperature close to that of surrounding seawater.

a. Their internal temperature changes with seawater temperature. An organism with this characteristic is called an ectotherm.

b. Ectotherms are commonly called “cold-blooded” organisms, and include terrestrial as well as marine organisms.

4. Other marine organisms, such as certain tuna and sharks, have an internal temperature that varies, but remains 9°–16°C warmer than the surrounding water. Organisms with this characteristic are called endotherms.

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5. Marine mammals and birds have an internal temperature that is relatively stable. Organisms with this characteristic are called homeotherms. Some endotherms have a body temperature above their surroundings, but it is not constant and varies with the surrounding temperature. Organisms with this characteristic are called poikilotherms.

a. Endotherms are commonly called “warm-blooded” organisms.

How does temperature affect metabolism? What’s the advantage of being an endotherm?

6. All organisms (marine and terrestrial) live within an ideal temperature range. However, they can tolerate some variations above and below their ideal range.

a. Ectotherms cannot generally tolerate temperatures much above their ideal range. Below their ideal range is generally more tolerable.

b. Endotherms tolerate a wide range of external temperatures because they maintain their own internal temperature.

c. Internal heat regulation allows endotherms to live in a variety of habitats. Their metabolic rate remains the same regardless of external temperature.

7. Being an endotherm (especially a homeotherm) has disadvantages.

a. Homeotherms in particular tolerate very little change in their internal temperature.

b. The high metabolic rate of both organisms demands a large food supply and efficient gas exchange.

C. Sound


Topic: Sound in the Sea


Code: LOP2195

How does water affect sound? How do some marine mammals use sound in water to their advantage?

1. Sound is energy that travels in pressure waves.

a. It can only travel through matter, which is why there’s no sound in outer space.

b. Sound travels well in air, but even better in water.

2. In distilled water at 20ºC/68ºF, sound travels 1,482.4 meters (4,863.4 feet) per second, which is about five times faster than in air.

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a. It travels through warm water faster than cool water, and it travels faster in deep water due to the pressure.

b. Much like light, sound bounces off suspended particles, water layers, the bottom, and other obstacles, and is eventually absorbed by water as heat.

c. However, sound travels many times farther through water than light does.

d. You can experience this by scuba diving or snorkeling in Hawaii or other areas frequented by humpback whales. Male humpbacks “sing” during mating season. Often you can hear their songs under water, even though there are no humpbacks in sight or within many kilometers.

3. Because sound travels effectively in water, marine mammals including dolphins and whales use echolocation to sense objects under water.

a. These organisms echolocate by sending out a sound wave, then sensing the reflected sound wave that bounces back off an object.

b. Dolphins and whales can determine an object’s size, distance, density, and position with echolocation. Some studies indicate that a dolphin can tell when a woman is pregnant.

4. As you’ve learned, deep water in the ocean is colder than the upper layers. However, pressure is greater with depth, too.

a. The result is that sound travels more slowly in deep water due to the cold, but only to a point.

b. At about 1,000 meters (3,280 feet), the increasing pressure begins offsetting the effect of lower temperature.

c. Beyond about 1,000 meters (3,280 feet), the speed of sound increases so that in very deep water it travels faster than at the surface. There’s some evidence that whales use deep water to transmit sound across thousands of kilometers of ocean.

D. Pressure


Topic: Satellite Oceanography


Code: LOP2200

What is hydrostatic pressure? What effects does it have on marine life?

1. Right now, you’re under pressure. If you’re at sea level, you’re under the pressure of the atmosphere, which is literally the weight of the air.

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a. Atmospheric pressure exerts a force of 1 kg/cm2. For simplicity, scientists sometimes measure pressure in terms of the atmosphere.

b. At sea level the pressure is one bar also called one atmosphere (imperial system, abbreviated “ata”).

c. “Bar” is always singular (i.e., 1 bar, 2 bar, 100 bar).

d. Technically an atmosphere is about 1% greater than a bar, but for practical purposes when discussing water pressure, you can treat them as equal.

2. Water weighs far more than air, so marine organisms exist in an environment with greater surrounding pressure than land-based organisms do.

a. Pressure exerted by water is called hydrostatic pressure.

b. Hydrostatic pressure is the weight of the water column above a given depth: a hydrostatic pressure of 1 bar or 1 ata.

c. At that depth, the total pressure is 2 bar—one bar from atmospheric pressure, plus one bar from hydrostatic pressure.

d. Therefore, a marine organism living at 10 meters (33 feet) experiences twice the pressure present at sea level. The pressure increases 1 bar for each additional 10 meters.

3. At 30 meters (98 feet), the pressure is 4 bar, or four times the surface pressure.

a. Thirty meters isn’t that deep considering that some marine organisms live thousands of meters deep.

b. Thirty meters is within the depth range of experienced scuba divers, so even humans can go to that deep. Why doesn’t hydrostatic pressure affect these organisms or divers?

4. The reason is that while the pressure can be great, it is the same inside marine organisms as it is outside. Living tissue is made primarily of water, which is (within limits) incompressible and transmits pressure evenly.

a. Since everything’s in balance, the pressure doesn’t crush or harm marine organisms.

b. Very high pressure can affect chemical reactions and metabolism, but only at extreme depths well beyond where the vast majority of marine life exists.

5. Hydrostatic pressure is primarily an issue only for organisms that have gas spaces in their bodies.

a. This is because gases compress, so hydrostatic pressure can distort or even collapse these spaces.

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have experienced this as discomfort in your ears. Your ears have an air space behind the eardrum, and the discomfort comes from the hydrostatic pressure pushing your eardrum in against the compressible air space.

Guided discussion question(s): Scuba divers wear a face mask to see underwater. This is yet another air space that is affected by hydrostatic pressure. Discuss what causes the pulling sensation on the diver’s face upon descent and what a diver can do to relieve the problem. Lead students to understand that the pulling sensation occurs when the air pressure inside the mask is less than the water pressure outside. The solid mask is too ridged to compress enough to increase the inside air volume to equal the outside water pressure. To increase inside air pressure, the diver exhales through the nose.

6. Many fish have a gas bladder that they use to control their buoyancy.

a. They must add or release gas from the bladders when they change depth to keep the pressure in balance.

b. Similarly, scuba divers learn to add air to the space in their ears (a technique called equalizing because it equalizes the pressure inside the air space with the pressure outside), which allows them to dive without discomfort.

c. Failure to equalize can cause the pressure to rupture the diver’s ear drums.

E. Size and Volume

How do surface-to-volume ratios change as cell size increases?1. Marine organisms thrive by getting all the resources they need

from the water around them.

a. Each cell gets the nutrients and gas it needs from the surrounding environment and excretes waste products into that environment.

b. Single-cell organisms, such as protozoa or bacteria, make these exchanges directly to and from seawater.

c. A multicellular organism, such as a sea cucumber or a fish, uses systems to gather nutrients and gas from the environment and excrete waste.

d. The cells within a multicellular organism make the exchanges via the organism’s systems rather than directly with the surrounding water.

Why is a high surface-to-volume ratio important to cell function?2. This brings up some questions: Why are all large organisms

multicellular? Why are single-cell organisms always small? Why couldn’t a single-cell marine organism be the size of a multicellular organism and thrive by exchanging nutrients, gas, and wastes directly from and to seawater?

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3. The reason is that for each cell to live, all gases, nutrients, and wastes must pass back and forth through the cell membrane. Although cells have many shapes, for the purposes of this discussion assume they’re roughly spherical.

4. The volume of a sphere increases with the cube of its radius, and the surface area increases with the square of its radius.

a. If a cell were to grow so its diameter were 24 times its original size, its volume would increase 64 times, but its surface area would increase only 16 times.

b. Therefore, as a cell gets larger, the ratio between the surface area (i.e., the cell membrane) and the volume declines.

c. The bigger the cell, the lower the surface-to-volume ratio, which means that there’s less relative area through which to exchange gases, nutrients, and waste.

d. That’s why a high surface-to-volume ratio is important for cell function, and why large organisms are multicellular rather than giant single cells.

F. Buoyancy

Guided discussion question(s): A boat can float despite the fact that its materials are denser than water, as evidence by boats made of metal, fiberglass, and cement. Some of the crude-oil supertankers are so enormous that their size is difficult to imagine. These ships are as long as some of the world’s tallest buildings. Why don’t large vessels sink?

1. Although pressure doesn’t affect marine organisms substantially, buoyancy profoundly affects life in water compared to life on land.

a. The principle of buoyancy states that an object immersed in a gas or liquid is buoyed up by a force equal to the weight of the gas or liquid displaced.

b. This is known as Archimedes’ Principle.

2. The fact that you’re immersed in air means that buoyancy is affecting you right now—an upward force equal to the weight of the air volume you displace.

a. Air isn’t very dense, though. If you were to figure out the weight of the air you displace, you’d discover that the upward force is so tiny that it has no meaningful effect. That’s why we don’t float in air.

How does buoyancy affect swimming and drifting marine organisms?3. Water is far denser than air (about 800 times), so buoyancy in

water is a significant force.

a. The density of seawater is almost exactly the same as that of most living tissue.


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b. This means that most organisms in water are buoyed up by a force nearly the same as their own weight.

c. Some organisms—from microscopic plankton to the great whales—live in the open ocean and never have contact with the bottom. It would be impossible for a bird to live without ever landing, yet in the marine environment this type of existence is not only possible, but common.

4. Some living tissue and organic structures like bone, teeth, and shells, have a greater density than water and therefore sink. Organisms have various adaptations to handle this.

a. As you’ve learned, some fish have gas bladders to control their buoyancy.

b. These bladders give them the buoyancy to offset the weight of bones or teeth. Other fish don’t have bladders because they hinder rapid depth changes.

c. These species may have light skeletons or produce tissue high in oil (oil is less dense than water and is therefore buoyant).

d. Some organisms produce ammonium chloride, which is less dense than seawater.

5. Still other organisms have different adaptations for dealing with buoyancy.

a. Large shell-bearing invertebrates don’t rely on a midwater existence and instead live on the bottom.

b. Planktonic organisms store food in lightweight waxes and oils, which provide buoyancy.

6. Because of buoyancy, marine organisms don’t have to expend much energy to offset their own weight compared to land-based existence.

a. This is what allows entire communities to exist simply by drifting in the ocean.

b. It allows many swimming creatures to live most of their lives without ever actually coming into contact with the bottom.

c. It allows organisms to grow larger than those on land. This is particularly evident in whales, which grow significantly larger than any terrestrial animal ever has, living or extinct.

d. Due entirely to weight, it would be physiologically impossible for a terrestrial animal the size of a blue whale to exist.

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G. Movement and Drag

What characteristics allow marine organisms to avoid sinking? 1. While marine organisms have an advantage over land-based

organisms with respect to buoyancy, the situation is reversed when it comes to drag.

a. Because water has a far higher viscosity than air, it resists movement through it far more than air does.

b. Consider what happens when you’re in a swimming pool—it takes very little effort to push yourself off the bottom thanks to buoyancy.

c. However, it takes far more effort to swim a long distance than to run the same distance. This is due to drag.

2. Viscosity affects small organisms, plankton in particular.

a. Their small size gives them little strength to swim through water, and yet they depend on remaining suspended for survival.

b. These organisms may have plumes, hairs, ribbons, spines, and other protrusions that increase their drag and help them resist sinking.

c. Many have buoyancy adaptations that help them remain suspended in the water column.

What characteristics do marine organisms have to handle water resistance?

3. Organisms that swim must contend with water drag.

a. Drag is the resistance to movement caused by friction with water (or any other gas or fluid).

b. Drag increases with viscosity, but also with the speed, shape, and size of the moving organism.

c. Reducing drag is important because it affects an organism’s ability to capture food or elude a predator.

4. Several adaptations help organisms overcome drag.

a. Some organisms move or swim very slowly so that drag isn’t a substantial factor.

b. Some excrete mucus or oil that actually lubricates the organism to “slip” through the water.

c. However, the most common adaptation is streamlining, which is having a shape that reduces drag.

5. Different shapes move through water with more or less drag.

a. Some shapes create significant turbulence, which is chaotic water movement. Turbulence increases drag.


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b. A teardrop or torpedo shape produces the least turbulence and allows an organism to swim with the greatest efficiency and lowest drag.

c. This is why fast-moving fish and other marine organisms have their characteristic torpedo shape. It is also why engineers design rockets, jets, submarines, sports cars, and other fast-moving craft with this shape.

Guided discussion question(s): Pick an organism and discuss the adaptations the organism has to reduce drag through the water. What advantages do these adaptations have over and above reducing drag, if any?

H. Currents

How does water movement affect the distribution and survival of marine life?

1. The buoyancy characteristics that allow marine organisms to exist midwater have an interesting advantage with respect to survival.

a. As you’ve learned, entire marine communities exist entirely in the open ocean, drifting in ocean currents without contact with shore or bottom.

2. Some marine organisms take advantage of this type of existence at some point during their life cycle.

a. For organisms to drift as larvae provides advantages over remaining in the same location as the original community.

b. First, drifting disperses the organisms to new habitats, maximizing the chances of species survival should something happen to the original community.

c. Second, drifting may take organisms to nutrient-rich areas, preventing too many offspring from competing for the same resources in the original community.

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Instructional Strategy – Student Self-Study Exploration Through ReadingGuide students to read and study each major topic of the chapter rather than focus on the entire chapter at one time. Before reading, focus students’ attention on the guided reading questions (green in the student textbook). These are listed here for each major topic.

For each major topic in the chapter assess students’ prior knowledge. Instruct students to construct a concept map, prior to reading, using the list of vocabulary words for each major topic of the chapter. If students need help constructing a concept map, review the directions with them.

As students read about the topic, have them answer the “Study Questions” located in the textbox on the first page of each section. After students read the section have them revise their concept maps. It may be beneficial to use a different colored pen or pencil so that students can see what they have learned from reading and where their misconceptions of the subject matter lie. If you have divided students into study groups they may share their individual concept maps with their group. Study groups may then construct a summary concept page based on the feedback of the other team members.


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I. The Physics of Water Guided Reading Questions

A. Heat and Heat Capacity1. What is heat? What is temperature? How do they differ?

2. What are the two common systems used to measure temperature? Which one is most used by scientists?

3. What is heat capacity? How do you measure it?

4. What implications does heat capacity have on Earth’s climate?

B. Water Temperature and Density5. What unique characteristics does water exhibit as it turns from vapor

to liquid to ice?

6. What is latent heat of fusion? What is the difference between sensible and non-sensible heat?

C. Latent Heat of Vaporization7. What is latent heat of vaporization?

D. Thermal Inertia8. What are thermal inertia and thermal equilibrium? Why are these

concepts important to life and Earth’s climate?

E. Ocean Water Density9. What are the relationships between the salinity, temperature, and

density of seawater?

10. How and why is the ocean stratified by density?

11. What are the three density layers of the ocean? Approximately what proportion of the ocean does each layer account for?

12. What is a thermocline?

VOCAbULARy absolute pressure•

calorie•

entropy•

electromagnetic spectrum•

halocline•

heat •

heat capacity•

latent heat of fusion•

latent heat of vaporization•

non-sensible heat•

pycnocline•

thermostatic effects•

viscosity•

Phases

thermal properties determines the

which are changed by the

Input or Removal of

Heat

which affectsdensity of

Water

which is the

Total kinetic Energy

and is expressed by

Heat Capacity

and is related to water’s high

which is

which is

High

and moderates

Temperature (Thermal Inertia)

Latent Heat (Nonsensible

Heat)

Fusion Vaporization

ofof

which is

80 Calories/Gram

540 Calories/Gram

which includes

Liquids

Solids

Gases

PHySICS OF WATER

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II. How Water Physics Affect Marine Life Guided Reading Questions

A. Light1. How does water scatter and absorb light?

2. What are the photic, euphotic, dysphotic and aphotic zones?

B. Temperature3. What advantage does ocean-based existence have over land-based

existence with respect to temperature?

4. What are an ectotherm, an endotherm, a homeotherm and a poikilotherm?

5. How does temperature affect metabolism? What’s the advantage of being an endotherm?

C. Sound6. How does water affect sound? How do some marine mammals use

sound in water to their advantage?

D. Pressure7. What is hydrostatic pressure? What effects does it have on marine

life?

E. Size and Volume8. How do surface-to-volume ratios change as cell size increases?

9. Why is a high surface-to-volume ratio important to cell function?

F. Buoyancy10. How does buoyancy affect swimming and drifting marine organisms?

G. Movement and Drag11. What characteristics allow marine organisms to avoid sinking? What

characteristics do marine organisms have to handle water resistance?

H. Current12. How does water movement affect the distribution and survival of

marine life?

(Concept map on next page)

VOCAbULARy Archimedes’ Principle •

atmosphere•

bar•

bioluminescence•

Boyle’s Law•

buoyancy•

chromatophore•

countershading•

drag•

dysphotic zone•

echolocation•

ectotherm•

endotherm•

euphotic zone•

eurythermal•

homeotherm•

hydrostatic pressure•

light•

photic zone•

spectrophotometer•

streamlining•

temperature•

thermal inertia•

turbulence•


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Unit 3


and

which isto give the ocean its

by reflecting off

Suspended Particles

Water Molecules

differentially by

first and last

divides the ocean into

which include

where

Photosynthesis Occurs

Temperature

which can be internally regulated by which cannot

be internally regulated by

Endotherms (Homeotherms)

Ectothermsincluding

Mammals, birds, & Large

Fish

including most

Marine Organisms

Sound

Pressure Wave

Water Than in Air

Temperature, Salinity, and

Pressure

is a

travels 4 times faster in

and faster with increases in

Echolocation

Marine Mammals

Topography of Seafloor

used for

by

used to study

Movement and drag

Marine Organisms

Adaptations

which have

buoyancy

Marine Organisms

Archimedes Principle

Adaptations

affects

which have

is explained by

Surface-to-Volume Ratio

Exchange of

Small Organisms

explains why

Large Organisms

Multicellular

Single-Celled

are

Hydrostatic Pressure

Pressure Exerted by

Water

is

boyle’s Law

is explained by

Atmosphere Pressure at 10

Meters

and equals

2 bar/ata

of

Marine Organisms

affects

Gas Spaces

with

include

Color Visible Light

Scattered Absorbed

Plankton

Red Colors

Water

blue Colors

Light Zones

Aphotic Zone

Photic Zone

Euphotic dysphotic

are

Nutrients

Wastes

Gases

affects

WATER PHySICS AFFECT

MARINE LIFE

is important for

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Chapter 9



ENRICHMENT EXPERIENCES

Elaborate (Integration of Other Sciences) 1. The Physics of Water (physical science, Earth science and space

science, science and technology, and science and inquiry).

Reference Sidebar page 9-6 and Figure 9-8 - The Global Heat Sponge.

4 Have students research and report on the research studies NASA scientists are conducting regarding computer model simulations on how Earth’s climate may be changing.

2. The Physics of Water (physical science, Earth and space science, and life science).

4 Reference Figure 9-16 - Hydrological cycle.

4 Have students construct their own drawing of the water cycle.

3. The Physics of Water (physical science and Earth and space science).

4 Reference Sidebar Uneven Solar Heating Results in the Seasons on page 9-12 and Figure 9-17 – Why are there seasons?

4 Have students construct their own drawing that explains the causes of Earth’s seasons.

4. The Physics of Water (physical science and science and inquiry).

4 Reference Figure 9-15 – Latent heat of vaporization and fusion in pure water.

4 Have students complete the Heat and Phase Change Worksheet and associated questions.

HEAT ANd PHASE CHANGE WORkSHEET

Instructions: Using the textbook, compare the following changes in phase of water. Identify the type of latent heat and the corresponding amount of calories required for water to change phases.

Phase Melting Phase Evaporating Phase

Ice

___>

Liquid

___>

Gas

Add ____ calories Add ____ calories

Latent heat of

_____________

Latent heat of

_____________

<____ <____

Remove ____ calories Remove ____ calories

Latent heat of

____________

Latent heat of

____________


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Unit 3


Questions:

A. What is the importance of water having the highest heat of fusion of any known substance? Ice does not change temperature until all of the water freezes and when ice melts, the water does not change temperature until all of the ice has turned to liquid. This is why ice cubes cool beverages effectively.

When ice forms, most of the energy lost is released to the atmosphere. Ice absorbs large amounts of heat in melting. Because of the high heat of fusion, ice acts as a thermostat keeping higher latitude water and atmosphere near freezing all year. As ice forms during the winter, latent heat is released to the atmosphere. As ice melts in the summer, heat is used. Because the heat lost or gained is latent heat, the seawater temperature is near freezing all year.

B. What is the importance of water having the highest heat of vapor-ization of any known substance? Water does not get any warmer until it all vaporizes (changes from a liquid to a gas). When you boil water, the temperature does not change, which is why boiling provides and even cooking temperature and why we feel colder when we first get out of a pool or bath.

Because the latent heat of vaporization is so high, large quantities of heat can be carried to the atmosphere through evaporation. In the atmosphere, the heat can be redistributed geographically. This means that areas where evaporation is slow and precipitation is high are warmed and areas where evaporation is high are cooled. Heat is transported from the low latitude ocean by evaporation and atmospheric circulation and released to the atmosphere through precipitation at higher latitudes.

C. Why is the latent heat of vaporization so much higher than the latent heat of fusion? When water vaporizes, all of the hydrogen bonds must break which requires more energy. When water freezes, only some of the hydrogen bonds must break.

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Chapter 9



5. The Physics of Water (physical science and life science).

4 Reference textbook page 9-21 and 9-22.

4 Have students complete the Comparison of Ectotherm and Endotherm worksheet.

Extension (Interdisciplinary Connections)

Marine Science and the Real World Questions

These questions provide students with an opportunity to apply major concepts in the chapter to real world situations. They are located at the end of the chapter.

Activity 1 – Scuba diving and the Physical Properties of Water

The technologies to dive using scuba (self-contained underwater breathing apparatus) are based on many properties of water that students have learned about in this chapter as well as the chemistry of air and water and human biology. This is the perfect opportunity to arrange for a local scuba diving instructor to give an in class presentation of scuba equipment.

Basic scuba equipment consists of a tank with compressed air, a regulator with a mouthpiece and a buoyancy control device (BCD). The regulator reduces the high pressure of the air in the cylinder to a usable level and delivers the air to the diver with each breath. The BCD is an inflatable device that allows a diver to change or maintain buoyancy.

COMPARISON OF ECTOdERMS ANd ENdOTHERMS

Instruction: Using the textbook, compare ectotherms and endotherms. Fill in the table.

Cold-blooded or warm blooded?

How does internal temperature compare to external

temperature?Examples benefits Costs

Ectotherm Cold-blooded. Varies with external. Fish, amphibians, reptiles.

Less energy required.

More limited to environment

Endotherm Warm-blooded. Does not vary with external. Mammals, birds, and some larger fish (tuna and sharks).

Can tolerate a wide range of external

High metabolic rate requires large food supply and efficient gas exchange.


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Unit 3


A. Boyle’s Law and Scuba DivingBoyle’s Law states that at a constant temperature, the volume of a gas will vary inversely with pressure while the density of the gas varies directly with pressure. Using the text and this statement, have students fill in the following table and answer the associated questions.

Questions:1. When a diver descends, the increase in pressure compresses

the air and reduced the size of air spaces, such as ears, lungs, and sinuses. How can a diver reduce the pressure in these air spaces?

A diver can equalize the pressure by blocking the nasal passage while attempting to exhale through it. This forces air into the spaces inside the ears and sinuses and relieves discomfort.

2. When a diver ascends, the decrease in pressure causes the volume of the air to expand. What should a diver do when ascending?

A person’s lungs can expand approximately 15 to 30 percent of their original volume without bursting. A diver should breath when ascending to equalize the pressure inside and outside the lungs. If a diver does not, his or her lungs may rupture.

3. Why is it more difficult to breath at deeper depths?

The density of a gas increases directly as the pressure increases.

B. Archimedes’ Principle and Scuba Diving Divers need to adjust the amount of air in their BCD to

descend, ascend, and maintain neutral buoyancy. Buoyancy is affected by the density of the surrounding water.

Questions:

1. Based on what you have learned about Archimedes’ Principle, would you need more or less air in your BCD to float near the surface in fresh water? Explain.

You would need more air, because freshwater is less dense than seawater and it is easier to sink.

bOyLE’S LAW ANd SCUbA dIVING

Instructions: Using your textbook fill in the following table.

depth (meters/feet).

Volume of Air (liters)

Pressure on Lungs (ATM)

density of Air (kg/liter).

0 1 1.0 1

10 (33) 1/2 2.0 2

20 (66) 1/3 3.0 3

30 (99) 1/4 4.0 4

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Chapter 9



2. Divers often need weights to help them descend. Would you expect to need more or less weight to descend in freshwater?

Divers would need less weight in fresh water than in seawater; fresh water is less dense.

Activity 2 – Hurricane Research

Understanding heat properties of both air and water is very important to scientists who study hurricanes and why some storms become more intense than others. In this activity, students will become a hurricane researcher. To begin, use the National Hurricane Center historical data on the National Oceanic and Atmospheric Administration’s (NOAA) website and fill in the following table.

1. Research Question and Hypothesis:

Next step is to develop a research question. Choose two variables (such as wind speed and air pressure or sea surface temperature and Saffir-Simpson Category). Ask students to write a hypothesis.

2. Have students construct a data table and record the specific data they need to answer their research question.

3. Have students construct a graph to show the relationship between the two variables.

4. Have students make a conclusion and explain their findings based on what they have learned in reading this chapter.

5. Have students continue their research on hurricanes and ask them to research the social and economic impact of hurricanes. What patterns can they find? How do hurricanes affect the economy of an area?

HURRICANE RESEARCH

Instructions: Fill in the table using the NOAA website.

date/Time

Location PressureWind Speed

Saffir-Simpson Category

direction of Hurricane/Speed of

Movement

Extent of Wind

from Center

Sea Surface Temperature


9-40

Unit 3


TEACHER’S NOTES

Documents

Chapter 09 - Water: A Physically Unique Molecule