Chemistry (Refresher)

Transcription

1 Chemistry (Refresher) Chemistry Principles: Atomic structure of elements Elements found in living cells: free elements, and elements in organic molecules Chemical bonds: ionic, covalent polar, covalent non-polar, and hydrogen bond Compounds and molecules Water basics and its importance for life (Outline) Chemical composition Chemical properties: Polarity of water- hydrogen bonding Physical properties adhesion and cohesion Water emergent properties important for life on Earth

2 An atom is a substance that cannot be broken down by chemical means Electron Neutron Nucleus Proton Orbital

3 Table 2.1

4 The periodic tables shows the atoms of all chemical elements Not all elements are found in the structural molecules that makes up living organisms First shell Hydrogen 1H Mass number 2 He 4.00 Atomic number Element symbol Electron distribution diagram Helium 2He Second shell Lithium 3Li Beryllium 4Be Boron 5B Carbon 6C Nitrogen 7N Oxygen 8O Fluorine 9F Neon 10Ne Third shell Sodium 11Na Magnesium 12Mg Aluminum 13Al Silicon 14Si Phosphorus 15P Sulfur 16S Chlorine 17Cl Argon 18Ar

5 99 % of living material is made of SPONCH atoms

6 Chemical Bonds Interaction between electrons of two elements leads to formation of chemical bonds Movement of electrons, Ionic, & Covalent bonds

7 Figure H 2 O 2 2 H 2 O Reactants Products Chemical reactions Making and breaking of chemical bonds Reactants are turned into Products

8 Chemical compound and molecules I. Compounds: elements held together by ionic bonds II. Molecules: elements held together by covalent bonds Covalent bonds of molecules non-polar covalent bond: equal sharing of electrons polar covalent bond: unequal sharing of electrons

9 Transfer of electron Na Sodium atom Cl Chlorine atom Na + Cl Sodium ion Chloride ion Sodium chloride (NaCl) Sodium Chlorine Sodium chloride

10 Name and Molecular Formula Electron Distribution Diagram Lewis Dot Structure and Structural Formula Space- Filling Model (a) Hydrogen (H 2 ) (b) Oxygen (O 2 ) (c) Water (H 2 O) (d) Methane (CH 4 ) Molecules

11 (slightly ) (slightly +) (slightly +)

12 Hydrogen Bond δ δ+ Water (H 2 O) δ+ δ Hydrogen bond Ammonia (NH 3 ) δ+ δ+ δ+

13 In a water molecule: - the hydrogen ends of the molecule have a slight positive charge - the oxygen end has a slight negative charge - the molecule as a whole is electrically neutral ons/hydrogenbonds.html (slightly ) (slightly +) (slightly +)

14 Hydrogen bond A Water molecule is polar molecule Water molecules are held by hydrogen bonds

15 Water makes life possible on Earth Chemistry and Physics of Water

16 Four emergent properties of water that contribute to the fitness of life on Earth 1. The universal solvent 2. Capillarity 3. Moderation of temperature 4. Expansion upon freezing 5. Water dissociation and ph

17 Water is the solvent of life solve.html δ + δ δ δ +

18 Hydrophilic (water-loving can dissolve in water) ionic and polar substances Hydrophobic (water-hating cannot dissolve in water) non-ionic and non polar substances

19 Cohesion along with adhesion help pull water up through the microscopic vessels of plants Two types of water-conducting cells Adhesion Direction of water movement 300 µm Cohesion

20 Surface tension is a measure of how hard it is to break the surface of a liquid

21 Moderation of temperature Santa Barbara 73 70s ( F) 80s 90s Los Angeles (Airport) 75 Burbank 90 Pacific Ocean 68 Santa Ana 84 San Bernardino 100 Riverside 96 Palm Springs s San Diego miles

22 Moderation of temperature Water acts as a heat sink on earth To cool the surrounding, heat is absorbed breaking the hydrogen bonds (Evaporation) Sweating? Heat is released when hydrogen bonds are formed (Condensation) Rain drop formation?

23 Water expansion insulates water bodies - Frozen water expands and is less dense than liquid water - Floating ice acting as an insulator - Lakes do not freeze allowing life to exist under ice Hydrogen bond Liquid water: Hydrogen bonds break and re-form Ice: Hydrogen bonds are stable

24 Dissociation of water molecules leads to acidic and basic conditions that affect living organisms H 2 O H + + OH - hydrogen ion hydroxide ion Concentration of each is 1 in 10 7 M = 1/10 7 = 10-7 M

25 Acids and Bases Acids substances when dissolved in water donate addition H + HCl H + + Cl - Bases substances when dissolved in water reduce the H + concentration by two ways: Directly accepting H + NH 3 + H + NH 4 + Indirectly by dissociating to form hydroxide ions (OH - ) which combine with H + in solution to form H 2 O NaOH Na + + OH -

26 ph Scale 0 Water and ph (Acidic and basic conditions) H + H+ H + H + OH OH H + H + H + H + Acidic solution OH OH H + H + OH OH OH H + H + H+ Neutral solution OH OH OH H + OH OH OH H + OH Basic solution Increasingly Acidic [H + ] > [OH ] Neutral [H + ] = [OH ] Increasingly Basic [H + ] < [OH ] Battery acid Gastric juice, lemon juice Vinegar, wine, cola Tomato juice Beer Black coffee Rainwater Urine Saliva Pure water Human blood, tears Seawater Inside of small intestine Milk of magnesia Household ammonia Household bleach 14 Oven cleaner