1. The Chemical Basis of Life

2.  All living organisms are made up of matter (anything that takes up space & has mass)  Matter is composed of elements (the basic substance or chemical that cannot be broken down)  There are about 25 essential elements necessary for life; 4 make up 96% of the human body (in this order): O, C, H, & N  Most of the other 4%: Ca, P, K, S, Na, Cl, & Mg  Trace elements are found in small quanti ties

3. http://www.emsb.qc.ca/laurenhill/science/table.jpg

4.  Look at your food labels. Most contain trace elements (ie. Fe, I, Cr, Co). Water is treated with F & I.  We need trace elements in our bodies. For example, Iodine (I) for the thyroid; Iron (Fe) for blood/O 2 transport; Flourine (F) for prevention of tooth decay  Compounds are substances of 2 or more different elements; ie. NaCl.  Pure Na is an explosive metal; pure Cl (chlorine) is a poisonous gas but when together they form an edible solid compound!

5. Atoms, meaning indivisible, are the smallest units of matter, contain particles: 1. Protons (p + ) have a positive charge and are located within the nucleus (center) of the atom. The proton # always remains the same. 2. Neutrons (n) have a neutral or no charge and are also located within the nucleus of the atom. 3. Electrons (e - ) have a negative charge and orbit the nucleus of the atom in a cloud.  They move in 3D, not just in a circle. They are separated by levels and the further away from the nucleus, the greater the energy they have.  These take place in chemical reactions (rxns).

6. An Atom: http://www.csmate.colostate.edu/cltw/cohortpages/viney/atom.jpg

7.  Elements have a unique # of p + ; this is the atomic number. Ex.) Helium (He) has the atomic # of 2 and has 2 p + ; C has 6 p + and the atomic # of 6.  Generally, the proton # = the electron #  Atomic mass is the p + + the n or the sum of the nucleus. Ex.) He = 4; C = 12 (b/c the mass of the p + = the mass of n)  When some atoms of the same element have different mass numbers, their n # is different. These are isotopes. The p + and e - are the same! Ex.) C-12, C-13, and C-14 (written 12 C, 13 C, and 14 C).  14 C is a radioactive isotope; this means the nucleus spontaneously decays (emitting radioactivity). This is used to date fossils.

8.  Na has 1 e - in its outermost shell; Cl has 7 e - in its outermost shell. Cl is anxious to gain 1 e - to fill the octet rule while Na is more than willing to give up that 1 e - to satisfy that rule.  Ionic bonds form as the result of e - transfer; 1 element gives/donates an e - while the other element receives/accepts the e -. In this case, Na donates, Cl receives.  These bonds result in atoms (or molecules) w/ electrical charges and are a.k.a. ions.  The compounds that formed are salts which exist as crystals in nature and readily dissolve in water. http://www.findhealer.com/gloss ary/images/salt.gif

9. http://chem.sci.utsunomiya-u.ac.jp/v9n2/MOzden/image/Figure7.jpg Ionic Bond between Na and Cl, forming NaCl:

10.  Covalent Bonds are strong bonds that share e - ; these form molecules.  These can be single (1 e - pair shared), double (2 e - pairs are shared, or 2 e - ) or triple (3 e - pairs are shared, or 6 e - ).  Some covalent bonds share e - equally; this is a nonpolar covalent bond. Ex.) H 2, O 2, CH 4 http://upload.wikimedia.org/wikibooks/en/c/c2/Covalent_bo nd_h.png http://www.dlt.ncssm.edu/TIGER/Flash/bonding/Coval entBonding-TN.gif

11.  However, most covalent bonds do not share e - equally. These are polar covalent bonds. Ex.) H 2 O.  Polar covalent bonds will result in a molecule that has atoms in a tug-of- war for the e - ; the more electronegative an atom is, the closer the e - will be to that atom.  Electronegativity is an atom’s pull, or attraction, for shared e - (that is, those e - in a covalent bond).  Note: for the scope of this course, O is the most electronegative atom (N & F are also electronegative)  Let’s look at H 2 O: O will pull the e - a little closer to itself, leaving the H’s slightly positive (the O will be slightly negative as a result). This means the e - will hang out more often with the O than the H’s.  B/C this molecule forms a polar covalent bond & each atom has a slight charge, this is a polar molecule. There is an unequal distribution of charges.

12. http://cache.eb.com/eb/image?id=96904&rendTypeId=4 http://www.makingthemodernworld.org.uk/learning_modules/c hemistry/03.TU.02/illustrations/03.IL.14.01.gif Polar Bonds: Water & Chloroform

13.  Hydrogen bonds are weak bonds that are crucial to the 3D shape of large molecules (DNA & proteins).  Can be found in molecules that have polar covalent bonds. Ex.) H 2 O + H 2 O  Are the reason for the properties of H 2 O.  Form between a H of 1 molecule AND a N OR O of another molecule.  They form and break quickly.

14. http://academic.brooklyn.cuny.edu/biology/bio4fv/page/image12.gif Water Molecules Oxygen Hydrogen

15.  The properties of water are made possible b/c of hydrogen bonds.  Water is a requirement of life & the properties of water make it essential to live. The properties of water include:  Cohesion, Adhesion, Surface Tension, Temperature Moderation, Existing in 3 States Naturally, & Solvent of Life  Cohesion is the ability/tendency of molecules (in this case H 2 O molecules) to stick together (to other H 2 O molecules).  IF water evaporates (from the leaves), water will travel up from the roots to the leaves b/c of cohesion (water sticks to water). This will also carry dissolved nutrients that the plant needs for survival. Cohesion : http://www.u413.com/images/Wallpaper/00838_drops_1280x1024.jpg

16.  Adhesion is the ability of one molecule to stick to something else; in this case H 2 O can stick to the veins or cell walls of the plant.  This is how capillary action occurs (water travels against gravity or up the plant thru the veins b/c water sticks to the sides of the plant’s walls). Through cohesion and adhesion, capillary action occurs. Adhesion & Capillary Action: http://www.waters.com/webassets/cms/category/media/other_images/primer_b_%20thinlayer.jpg

17.  Surface Tension is the difficulty of H 2 O to stretch or break; H 2 O has a high surface tension (difficult to break).  Water’s moderate temperature is due to the H Bonds. H 2 O can resist temp changes; this keeps the Earth’s temp within limits (to sustain life).  Due to the large volume of H 2 O on Earth’s surface, climate is regulated. Water stores heat (from the sun) during warm times and releases heat during cold times.  Heat is the amount of energy to move atoms and molecules.  Temperature is the measurement of heat (average speed of atoms and molecules, not the total amount of heat).  Evaporative cooling is the process of heat escaping from the body in the form of sweat. As sweat evaporates from the skin, cooling results.

18. Surface Tension: Jesus Lizard walking on Water: Can Cohesion, Adhesion, and Surface Tension occur independently? http://www.societyofrobots.com/images/robot_JB_lizard1.jpg

19.  Water exists naturally in 3 states: as a solid, liquid and a gas (water vapor).  When water freezes, it is less dense than when it is in liquid form. Why? H Bonds!  The H Bonds stabilize & hold a crystalline pattern (at arms length). This allows ice to float on water (in the liquid state).  This is an important property b/c only the top layer of water (in a body of water) will freeze & it will not sink.  This allows life in the water environment to survive. Also, the ice insulates the water (like a blanket from the cold air).

20. http://ngm.nationalgeographic.com/2007/06/vanishing-sea-ice/img/vanishing- sea-ice.jpg Frozen Oceans: http://www.naturetrek.co.uk/pics/t146-large1.jpg

21.  Water is the solvent of life; this means it can dissolve many substances (due to its polarity).  When water is a solvent (agent that dissolves) & forms a solution (a liquid with 2 or more substances mixed together), water is an aqueous solution.  The solute is the dissolved substance (salt, sugar, etc).  This property is important to life b/c many substances (polar and/or ionic) must be transported in the body (an organism). Ex.) Blood’s main component is H 2 O and is contains dissolved ions, salts, gases, wastes, sugars, and proteins for transport.

22.  The hydrogen ion is the H + and cannot exist alone.  The hydroxide ion is the OH - and can exist alone.  The hydronium ion is the H 3 O +. Why is this important to life?  Ions regulate pH.  The pH Scale is a range of numbers that indicate the amount or concentration of H + or OH - in a solution. It ranges from 0-14.  A neutral solution is a solution that has an equal concentration of both ions. The pH is 7 (mid-range). Pure water is neutral.  An acidic solution is a solution that has an increased concentration of H+. It has a low pH (below 7). More H+, less OH-, low pH.  A basic solution is a solution that has an increased concentration of OH-. It has a high pH (greater than 7). Less H+, more OH-, high pH.

23.  Human Blood is ~ 7.3-7.4 (a person cannot live below 7 or above 7.8).  Buffers are substances that stabilize pH. http://www.epa.gov/acidrain/education/site_students/images/phscale.gif

24. Chemical Reactions- making and breaking bonds. __H 2 + __ O 2  __H 2 O  Reactants (starting materials)  Products (results)  Always balance equation! This means the # of atoms (H, O, etc) on the left side of the equation MUST equal the # of atoms (H, O, etc) on the right side of the equation. Try this:  __C 6 H 12 O 6 + __O 2  __CO 2 + __H 2 O

25.  C 6 H 12 O 6 + 6 O 2  6 CO 2 + 6 H 2 O6 C12 H18 O