1. Lesson 2: Water on earth
Chemistry of water

2. Blue Marble Animation Things to consider while you are watching….
What observations can you make about this animation of Earth rotating?
Does the northern or southern hemisphere contain more land?
Which ocean basin is the largest?
When showing animation, invite students up to the screen to point out north atlantic, south atlantic, north pacific, south pacific, indian, arctic ocean basins

3. Blue Marble Animation Things to consider while you are watching….
What observations can you make about this animation of Earth rotating?
Ocean dominates the surface area of the globe, land appears green and brown, lines and ridges in the oceans, oceans are interconnected, ice near the poles
Does the northern or southern hemisphere contain more land?
Northern hemisphere
Which ocean basin is the largest?
pacific
When showing animation, invite students up to the screen to point out north atlantic, south atlantic, north pacific, south pacific, indian, arctic ocean basins

4. Ocean Facts Ocean covers approx. 71% of earth’s surface Four oceans
Pacific, atlantic, indian, arctic
97% of earth’s water is saltwater
3% of earth’s water is freshwater
1% is liquid
2-3% contained in glaciers and sea ice caps in polar regions

5. Earth’s 4 “spheres” are constantly changing
Hydrosphere – water
Bodies of marine animals are 80% water by mass
Biosphere- life
Atmosphere – air
Lithosphere - land

6. Ocean as a resource
Renewable resource – ocean replenishes itself naturally over relatively short periods of time
Constant influx of water from rivers and rain
Nonrenewable resource – exhausted faster than they are naturally replaced
Ex: natural gas and minerals
Humans must be careful to use ocean resources wisely
Ex: overfishing

7. Water for thought….
Compare and contrast salt water and freshwater.

8. Lab: Freezing, melting, and boiling

9. Water chemistry review
Flip to appendix B
Atoms
Basic particle of a unique element
Nucleus
Neutrons: no electrical charge
Protons: +1 charge
Electrons: -1 charge
Approx 90 different naturally occurring elements

10. Neutrons protons Valence electron shell (outer most shell) NEUTRONS

11. Atomic Number (Protons)
Isotopes
Scientists use variations of isotopes to research earth’s climate over many years
Studied in ice core samples, sea shells, or cave formations
Isotopes are variations of the same element that have same number of protons, different number of neutrons.
Ex:
“Heavy Oxygen” 0-18
“Light Oxygen” O-16
Atomic Number (Protons) 8
Atomic Mass 18 16
Neutrons 10

12. Molecules & bonding
Oxygen and hydrogen are usually not found alone in a natural state
Two or more atoms bond together to form molecules or compounds
Atoms or molecules are more stable when they have a complete outer shell
Bonding – interactions between 2 atoms to fulfill octet rule
Covalent – when 2 atoms share electrons
Ionic – when 1 atom transfers an electron to another atom

13. water Asymmetrical combination of 1 oxygen and 2 hydrogens Polar
Oxygen end slightly negative while hydrogen end slightly positive
Hydrogen bonding
Attraction of negative oxygen of 1 water molecule to positive hydrogen of another water molecule
Leads to cohesion or “stickiness” of water molecules to one another
Also leads to adhesion or “stickiness” of water to other substances

14. Water and density
Hydrogens bonds are relatively weak in comparison to ionic and covalent
However, collective h bonds are quite strong
One water molecule can h bond to 4 other water molecules
Hydrogen Bond

15. How temperature affects water
water molecules are situated as closely as they can be at 4˚C.
Highest density in liquid state
Below 4˚C, hydrogen bonding gets stronger and water molecules space out
Forms lattice structure and becomes solid ice
Water expands as it freezes
Becomes less dense
Most substances are more dense in solid state

17. Check for understanding
With your partner, answer the following checkpoints.
Distinguish between atoms and molecules
What is density? How does the polarity of water molecules relate to the density of water?

18. Got it? With your partner, answer the following checkpoints.
Distinguish between atoms and molecules
Atoms are the smallest unit of an element. Molecules are formed when 2 or more atoms combine.
What is density? How does the polarity of water molecules relate to the density of water?
Density is how compact a substance is – the mass of a substance divided by a given volume. Water molecules are polar covalent and therefore form hydrogen bonds with one another. The hydrogen bonds do not allow water molecules to move closer together and become more dense when water gets colder than 4˚C. Solid ice is less dense than liquid water.

19. Think break…
How would life in the polar regions change if water behaved like a normal substance at decreased temperatures?

21. Changing phases of matter
Misconception = students do not believe temp of solids and gases will increase. Many students think ice is always 0. however, the molecules hold a certain amount of heat and as a result measure a certain temp. Ice in a freezer has a temp of less than 0 if the temp in freezer is less that -10, then so is the ice.

22. Phase change
During a phase change, temperature stays the same but heat energy continues to be added.
Heat is absorbed and melts a solid into a liquid
Same thing happens from liquid to gas; this is called vaporization or evaporation
The heat absorbed during a phase change is called latent heat

23. Heat capacity
Water has tremendous ability to resist changes in temperature
Amount of heat needed to raise temp of 1g Water 1˚C is 1 calorie.
During cooling energy is taken away or given off
Freezing is when water changes from liquid to solid
Condensation when water changes from gas to liquid

25. Phase Change Practice
Sketch a phase change diagram for isopropyl alcohol (rubbing alcohol)
Freezes at -85.5˚C
Boils at 82.3˚C
Label the following: solid, liquid, gas, freezing, melting, condensation, vaporization

26. Phase change practice

27. Lab 2: floating and sinking

28. Density and marine organisms
Buoyancy – the upward force that keeps materials afloat
Have you ever lifted up someone in the water? Heavier or lighter?
What happens to the water level when you add something to a cup of water?
This is called displacement
Ask students if they can float or not, has anyone gone scuba diving? Critical to regulate buoyancy.
Ballast water often contributed to invasive species. An example in the Great lakes is the zebra mussle, which is native to lakes and seas in Eurasia. In US, they have damaged equipment, including boats, water treatment plants, and more, as they colonize on hard substrate.

29. Density and marine organisms
Things float better in seawater than freshwater
This is due to density
Freshwater: 1.00 g/cm3
Saltwater: 1.03 g/cm3
Ask students if they can float or not, has anyone gone scuba diving? Critical to regulate buoyancy.
Ballast water often contributed to invasive species. An example in the Great lakes is the zebra mussle, which is native to lakes and seas in Eurasia. In US, they have damaged equipment, including boats, water treatment plants, and more, as they colonize on hard substrate.

30. Density and marine organisms
Aquatic organisms use buoyancy and displacement to maintain neutral buoyancy
Ex: phytoplankton have oil deposits in shells
Oil is less dense than water
Ex: jellyfish
Animals that are 90% water, some float on surface, some rely on neutral buoyance to maintain position in water column
Ex: sargassum
Seaweed with air sacs
Allows for ample light absorption for photosynthesis

31. Moon jellyfish
Moon jellyfish

33. Polar bear sea ice animation
Marine organisms are also affected by density of water’s solid form
Animals in polar regions are very dependent on sea ice
Polar bears, penguins, fish
Insulates water below
Reflects sun

34. Got it?
What is buoyancy? How does it allow large objects like massive whales to float?
Describe how the structure of the sargassum helps it to float on water.
How does the fact that ice floats affect marine animals?
Describe the relationship between the movements of the polar bear and the seasonal changes in sea ice. How can you explain this relationship?

35. Got it?
What is buoyancy? How does it allow large objects like massive whales to float?
Buoyancy is an upward force exerted on objects in a fluid. The buoyant force is equal to the weight of the water displaced by the object. In the case of a large whale, the whale displaces a tremendous amount of water and the buoyant force helps the animal to float.

36. Got it?
Describe how the structure of the sargassum helps it to float on water.
Sargassum has gas-filled “bubbles” that are less dense than water, helping it to float.

37. Got it? How does the fact that ice floats affect marine animals?
Animals such as walruses, polar bears, seals, and penguins can rest on the ice between sessions of hunting for prey. The ice also provides an ideal place for these animals to raise their young.

38. Got it?
Describe the relationship between the movements of the polar bear and the seasonal changes in sea ice. How can you explain this relationship?
The polar bear seems to follow the ice. Polar bears rest on the ice as they hunt their prey, primarily seals.