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The Science of Water :

The Science of Water We are surrounded by water; we are made of water

Water in our World:

2 Source: http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-earth.html Water in our World Water is necessary for life Water in our atmosphere helps to keep the planet warm Our bodies are composed of and dependent on water

A Quick Overview:

3 A Quick Overview Of some of the science basics What are some of the properties of water that make it so essential to life on our planet?

All Matter is Composed of Atoms:

4 All Matter is Composed of Atoms neutron proton + proton proton + neutron neutron + The atom is composed of A nucleus made of neutrons and protons An electron “cloud” composed of electrons Representation of a nucleus Protons and neutrons have nearly identical masses, but their charge is different Protons have a positive (+) electrical charge and neutrons do not have an electrical charge

Subatomic Particles Composing the Atom:

5 Subatomic Particles Composing the Atom Subatomic Particle Charge Size Location Proton +1 1 Part of the nucleus Neutron 0 1 Part of the nucleus Electron -1 0 Electron “cloud” (outside of the nucleus)

The Quantum Atom:

6 We can only describe areas of probability where we might find an electron Electrons are constantly moving Electrons have a specific amount (quantum) of energy, related to their position from the nucleus The Quantum Atom Source: http://physics.usc.edu/~bars/135/LectureNotes/QuantumMechanics.htm Red dots represent areas of probability 1 Angstrom


7 Probability Suppose you had a new dartboard. What would it look like after you had played darts with it for six months? Can you predict accurately where the next dart you throw will go? Can you predict an area where the next dart is likely to go? Source: www.amisane.org/images/dartboard2.jpg


8 Question Why do we care about what atoms are made of?

Electric Charge:

9 Electric Charge Electric charge is a basic force that causes movement Like charges repel + Unlike charges attract - - + + -

Net Charge of an Atom or Ion:

10 Net Charge of an Atom or Ion The charge on any substance is a result of the total number (#) of Protons (p) + charges, in the nucleus, and Electrons (e-) - charges, outside the nucleus If the # of…. then the net charge is…. p = e- neutral (atom) p > e- positive (ion) e- > p negative (ion)

Atoms Bond:

11 Atoms Bond The outer electrons of both atoms are mutually attracted to the nuclei Oppositely charged particles form a bond, representing a lower energy state for each of the atoms, releasing energy Source: ibchem.com/IB/ibfiles/ bonding/bon_img/cov3.gif Nature always wants to be in the lowest energy state!

Why are Bonds Formed?:

12 Why are Bonds Formed? Bonds are formed because of the electrostatic attraction between atoms. In doing so, the atoms achieve a lower energy state.

Ionic Bond: Chlorine (Blue) Grabs Electron from Sodium (Red) :

13 Ionic Bond: Chlorine (Blue) Grabs Electron from Sodium (Red) Click the image above to view the animation in your web browser, or go to http://nanosense.org/download/finefilters/Nacl_SD.mov Source: http://visservices.sdsc.edu/projects/discovery/Nacl_SD.mov

Forming a Water Molecule:

14  – +  +  A water molecule Orbital representations of hydrogen and oxygen Forming a Water Molecule Unequal attraction to bonding electrons Oxygen is a strong electron grabber (high electronegativity) Hydrogen’s electron cloud tends to hang out close to oxygen, leaving H’s positively charged nucleus all by itself – –

Electron Density is Uneven:

15 Source: http://www.llnl.gov/str/October05/Mundy.html Electron Density is Uneven The average electron density around the oxygen atom in a water molecule is about 10 times greater than the density around the hydrogen atoms This non-uniform distribution of positive and negative charges, called a dipole, leads to the substance’s unusual behavior A water molecule, with electron density represented by the shaded blue areas

Water is a Polar Molecule:

16 Water is a Polar Molecule The unequal distribution of charges on the water molecule make it a polar molecule One end is more negative, and one end is more positive More positive ends More negative end A water molecule  - means partial negative charge  + means partial positive charge

Hydrogen Bonding I:

17 Source: http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page3.html Hydrogen bonding between water molecules Hydrogen Bonding I The partial negative end of the oxygen atom is attracted to the partial positive end of the H atom on an adjacent molecule Hydrogen bonds give water its unique properties

Hydrogen Bonding II:

18 Hydrogen Bonding II Click the image above to view the animation in your web browser, or go to http://www.northland.cc.mn.us/biology/Biology1111/animations/hydrogenbonds.html

Hydrogen Bonding Representation:

19 Source: www.personal.psu.edu/.../ bonddiagram.gif Hydrogen Bonding Representation In water, hydrogen bonds form between the partially negatively charged oxygen atom and the partially positively charged hydrogen atom Water molecules, with the hydrogen bonds represented by the dotted lines

Unique Properties of Water:

20 Unique Properties of Water Universal solvent Exists in nature as a solid, liquid, and gas The density of ice is less than liquid water High surface tension High heat capacity Exists as a liquid at room temperature

High Surface Tension:

21 High Surface Tension Allows water to form drops Allows water to form waves Water drops can “adhere” to surfaces even though gravity is pulling on them Source: Photo 2004 Edward Tsang


22 Can You Explain Why this Drop Sticks to the Leaf and Grows Larger? Source: http://www.azeemazeez.com/photos/wallpaper/water800.jpg


23 Or How this Spider Can Walk on Water? Source: http://static.flickr.com/82/237875014_4d579d57c5.jpg

Adhesion :

24 Adhesion Adhesive forces are attractive forces that occur between two unlike substances Source: http://www.wtamu.edu/~crobinson/SoilWater/meniscus2.jpg In a narrow glass tube Water molecules are more strongly attracted to the tube than they are to each other (cohesion) The cup shape formed at the top of the water is called a meniscus

Water Climbs Trees!:

25 Water Climbs Trees! Evapotranspiration The tiny tubes in the root hairs suck up water from the soil Inside the plant are more hollow tubes (xylem) for transporting water through the plant Finally, water exits the plant through the tiny openings in its leaves (stomata) Source: Adapted from http://www.ualr.edu/botany/transpiration2.gif

High Specific Heat Keeps Beaches Cooler in the Day and Warmer at Night!:

26 Source: http://www.exodus.co.uk/pictures/d03hp120c.jpg High Specific Heat Keeps Beaches Cooler in the Day and Warmer at Night! Specific heat The amount of energy required to change 1 gram of a substance 1 o C Water has high specific heat Absorbs large amounts of heat energy before it begins to get hot Releases heat energy slowly Moderates the Earth's climate and helps living organisms regulate their body temperature

Solid, Liquid, and Gas:

27 Source: http://www.eskimo.com/~captain/slidesho/Lake_Twenty_Two_Partly_Frozen_Over_and_Snow_Covered.jpg Solid, Liquid, and Gas Water is the only substance which exists under normal conditions on earth as a solid, a liquid, and a gas

Ice is Less Dense than Water I:

28 Ice is Less Dense than Water I Density of H 2 O at different temperatures Temperature o C Density g/cm 3 0 (solid) 0.9150 0 (liquid) 0.9999 4 1.0000 20 0.9982 100 (gas) 0.0006 Source: http://www.wildthingsphotography.com

Ice is Less Dense than Water II:

29 Ice crystal Crystal lattice structure of ice Ice is Less Dense than Water II This is a very rare property! Sources: http://www.learner.org/jnorth/images/graphics/t/ice_crystal_Greg_Rob.jpg http://www.solarnavigator.net/images/ice_crystal_lattice.gif


30 Questions Can you imagine if ice did not float? How do you think that would affect the world?

Ice Melting:

31 Ice Melting Notice that ice has an open lattice structure that collapses when it melts Click the image above to view the animation in your web browser, or go to http://nanosense.org/download/finefilters/MeltingIce.mov

Water is a Universal Solvent:

32 Water is a Universal Solvent Water is a polar molecule with one end more positive and one end more negative Being polar allows water to dissolve nearly any substance with an unequal distribution of charges Water is the best substance that is universally used for transporting dissolved substances Source: http://www.chemistryland.com/CHM107Lab/Lab7/Slime/PourStirPoly2.jpg Water dissolves more substances than any other liquid

Important Points:

33 Important Points What are water’s unique properties? What is water’s structure, and how does it cause these properties? What would our world or life be like without water?

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