1. Chapter 2 Chemistry of Life Dr. Joseph Silver

2. this chapter deals with - structure of atoms - how atoms form molecules - the periodic table - the uniqueness of water - acids and bases - biologically important molecules

3. anything that has mass (made up of atoms) and occupies space (no matter how small) is called matter

4. the word atom was used 2000 years ago in Greece and we still are learning more about atoms today

5. scientists have done many experiments which show that one or more electrons (-) circle about a nucleus containing protons(+) and neutrons(0 no charge) scientists have found about 16 particles which make up atoms but for this course 3 is OK

8. atomic number = number of protons in an atom atomic mass = mass of protons+neutrons+electrons electron mass is so small that it contributes very little to the mass of an atom

11. remember mass represents the amount of matter in any atom, molecule or anything else weight represents the amount of force gravity exerts on a substance if you go to Mars your weight changes but your mass does not change

13. the nucleus of an atom has protons and neutrons packed into the center of the atom and the electrons are located in circular orbits (orbitals) or layers about the nucleus -electrons travel so quickly that we cannot see one -they do not fly off due to their attraction to the nucleus -atoms with large atomic numbers have many orbital layers

15. when protons are equal to electrons - neutral atom when protons do not equal electrons – atom is an ion if there are more protons than electrons – positive cation if there are more electrons than protons – negative anion

17. C12 = 6P + 6E + 6 neutrons C13 = 6P +6E + 7 neutrons C14 = 6P + 6E + 8 neutrons atoms of an element with different number of neutrons are called isotopes some isotopes release radioactive energy as the extra neutrons are released

19. isotopes have many uses in industry, medicine, chemistry, and biology one use is to date the age of fossils isotopes have a half life we know how long it takes for one-half of the energy in an isotope to disappear and we use this information to compare the amount of an isotope in new material and in a fossil and arrive at the age of the fossil

22. electrons determine the chemical behavior of atoms when the outer electron shell of an atom is not full it will give away electrons, or get electrons from other atoms, or share electrons with other atoms in order to have the outer shell filled

23. the farther an electron is from the nucleus the greater is the energy of the electron likewise the closer to the nucleus the less energy in an electron

24. for the purpose of this class any layer or orbital past the second orbital is filled by 8 electrons

25. the electrons in the outer shell of an atom are referred to as valence electrons and these are the electrons available for chemical reactions

27. an atom with 7 electrons in the outer shell would love to find an atom to give it 1 electron and an atom with 6 electrons in the outer shell would love to find an atom to give it 2 electrons or 2 atoms to each give it 1 electron

28. in atoms with multiple shells gaining electrons can fill the last orbital level or giving away electrons can empty the last shell and the lower level shell which is already filled will become the outer layer

29. on page 37 there is a picture of a periodic table it shows the 90 naturally occurring elements and the 28 man made elements

30. in the periodic table the elements are arranged according to their atomic number (the number of protons or electrons) they are arranged in columns according to the number of electrons in the outermost orbital shell and rows of increasing electrons

31. the electrons in the outer shell are called valance electrons these are the electrons which are involved in chemical reactions

33. an element with 1 electron in the outer shell can readily interact with an element having 7 valence electrons an element with 1 valence electron can also readily interact with elements having 6 valence electrons by exchanging or sharing electrons they fill the outer shells and form compounds with stable atoms

35. oxygen has 6 electrons in its outer shell two oxygens share 4 outer electrons making an outer shell in each atom with 8 electrons thus each has a full outer shell with 8 electrons forming a covalent bond usually stronger than ionic bonds the electrons travel so fast that it is as if the 8 electrons are in both atoms at the same time

38. the ability of atoms to form chemical bonds is influenced by - temperature (2x for every 10C) - concentration -catalysts (enzymes) - pressure (keeps atoms closer together)

43. WATER liquid at room temperature ¾ of earth’s surface covered by water polar covalent bond water has 2 single covalent bonds water molecules bond to each other by hydrogen bonds water becomes or has cohesive – adhesive – high specific heat high heat of vaporization – low density of ice - universal solvent - surface tension

48. each water molecule has 2 weak positive and 2 weak negative charges these charges attract water molecules and form weak hydrogen bonds – trillions of them – actually more - causing all water molecules to be attached to all of the other water molecules allowing water to have a high surface tension – a pin gently placed on water will float – a lizard can run across a pond – and insects can walk on water

49. the weak polar charges of water are attracted to other polar charges - water makes polar surfaces wet meaning they interact with each other they dissolve unlike non polar oils which form a ball and do not interact with water

50. a gram of water can hold more heat (specific heat) than any other biologically active compound if the heat generated by the chemical processes which keep you alive were not removed your body would literally go up in flames water in your blood and sweat picks up this heat and brings it to the surface where it leaves through your skin and lungs

52. it takes more heat to evaporate 1 gram of water (high heat of vaporization) than any other biologically active molecule so water is able to remove large amounts of heat as sweat is evaporated from your body and blood vessels bring heat to your skin

54. a gallon of water weighs more than a gallon of ice ice is less dense than water that is why ice floats this is very important think about this

55. you live in upper Michigan it is 20 below zero the ice on the lake is really thick now what will happen if the ice gets thicker and thicker and sinks to the bottom of the lake YES all plants and animals in the lake just got crushed to death

56. as you walk on the ice covering the lake the air temperature is 20 below zero what is the temperature of the water under the ice? Since water freezes at 0C or 32F then the water below the ice is much warmer than the temperature of the air in the middle of winter the water under the ice can be 50, 60, 70 degrees warmer than the air the insulation of the ice preserves life in the lake

58. water is a universal solvent more things dissolve or get wet in water than any other molecule think of all the chemicals and molecules that are in your body which dissolve in water

59. here is a new word mole a mole is the weight of any substance in grams that corresponds to the atomic masses of all of the atoms in that molecule of that substance 1 mole of any substance contains 6.02 x 1023 molecules scientists use this information to know how much reactant and product are present

60. if we have a glass of pure water what do we have in the glass?

61. if you said pure water that is a logical answer but it is not the correct answer

62. water can spontaneously split to form ions H2O splits to form H+ and OH- H = a positive hydrogen ion (a proton) OH = a negative hydroxyl ion for every 10 million molecules of water 1 molecule splits into H and OH

63. 1 out of 10 million is 1/10,000,000 or scientifically 10-7

64. thus in pure water the concentration of H is 10-7 and the concentration of OH is they are equal and neutral no charge

65. what is an acid? a substance which adds H+ ions to a solution if there are more H ions in a solution than OH ions then it is an acid

66. what is a base? a substance which add OH ions to a solution if there are more OH ions than H ions then it is a base

69. in pure water the H ions and the OH ions are equal so water is not a base nor is it an acid so pure water is neutral

70. because most people do not want to be speaking in scientific terminology like negative 6 or negative 12 scientists removed the negative attributes and called pure water (pH 7) where did the 7 come from from 1 part in 10 million

71. the pH scale goes from 0 to 14 the amount of H and OH always adds up to 14 so at a pH of 4 the concentration of H is 10-4 and the concentration of OH is remember minus 4 is more than minus 10

72. at a pH of the concentration of H is and the concentration of OH is minus 2 is much greater than minus 12

73. so an acid has more H than OH and a base has more OH and H and the farther away from 7 the more concentrated an acid or base becomes

77. pH is calculated on a log scale as you move 1 number (from 7 to 6 or 7 to 8) the concentration increased 10 times and as you move 2 numbers the concentration increases 10 x 10 or 100 times think back to math class and working with exponents

78. in your body you have many chemical processes which produce acids and bases your body in order to work efficiently must keep the pH of your body around this is done by a series of chemicals known as buffers

79. buffers are compounds which when reacted with a base release an acid, salt, or water and when reacted with an acid release a base, salt, or water the goal is to keep the pH of the body optimum

80. HCl + NaOH  HOH + NaCl acid + base  water + salt a buffer releases H ions when a base is added or releases OH ions when an acid is added

82. the action of a buffer is to resist a change in pH in our bodies there are 2 important buffers carbonic acid and bicarbonate