Lesson 2: Water on earth Chemistry of water

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

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

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

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

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

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

Lab: Freezing, melting, and boiling

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

Neutrons protons Valence electron shell (outer most shell) NEUTRONS

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

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

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

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

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

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?

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.

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

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.

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

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

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

Phase change practice

Lab 2: floating and sinking

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.

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.

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

Moon jellyfish Moon jellyfish

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

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?

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.

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.

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.

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.