Chemistry (Outline) Water (Outline) - Polarity of water- hydrogen bonding - Emergent Physical properties of water - Importance for life on Earth

Transcription

1 Chemistry (Outline) Chemistry Principles: Atomic structure of elements Elements found in living cells: free elements, and elements in organic molecules Chemical bonds: compound and molecules (Polar and nonpolar molecules) Water (Outline) - Polarity of water- hydrogen bonding - Emergent Physical properties of water - Importance for life on Earth

2 Ascending Non-living Atoms/Elements Molecules Chemical world Organelle Cell Living Tissue Organ Organ system Organism Biological World (Family) Population Community Descending Ecosystem Biosphere

3 Major Events in the History of Earth Cenozoic Humans Land plants Animals Origin of solar system and Earth From chemistry to biology Multicellular eukaryotes 1 Proterozoic eon 2 Archaean eon 3 4 Single-celled eukaryotes Atmospheric oxygen Prokaryotes

4 What s in our food? - Chemical elements ( ) - Elements in biological molecules

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

6 Table 2.1

7 The periodic tables shows the atoms of all chemical elements Not all elements are found in the structural molecules that makes up living organisms

8 99 % of living material is made of SPONCH atoms

9 Chemical Bonds Interaction between electrons of two elements leads to formation of chemical bonds 2 H 2 O 2 2 H 2 O Reactants Products Chemical reactions Making and breaking of chemical bonds Reactants are turned into Products

10 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

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

12 Molecules

13 (slightly ) (slightly +) (slightly +)

14 Hydrogen Bond

15 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 +)

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

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

18 Four emergent properties of water that contribute to the fitness of life on Earth 1. Cohesion of its molecules 2. Moderation of temperature 3. Expansion upon freezing 4. The universal solvent

19 Cohesion along with adhesion help pull water up through the microscopic vessels of plants Water conducting cells 100 µm

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

21 Moderation of temperature To break hydrogen bonds heat must be absorbed (Evaporation) Sweating? Heat is released when hydrogen bonds are formed (Condensation) Rain drop formation?

22 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 Ice Hydrogen bonds are stable Liquid water Hydrogen bonds constantly break and re-form

23 Water is the solvent of life solve.html

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

25 ph scale Battery acid Water and ph (Acidic and basic conditions) Increasingly ACIDIC (Higher H + concentration) Lemon juice, gastric juice Vinegar, cola Tomato juice Acidic solution Rainwater Human urine NEUTRAL [H + ]=[OH ] Saliva Pure water Human blood, tears Neutral solution Seawater Increasingly BASIC (Higher OH concentration) Milk of magnesia Household ammonia Basic solution Household bleach Oven cleaner

26 Acid Precipitation, a serious threat to the Earth s ecosystems, is caused by the presence in the atmosphere of Sulfur dioxide and Nitrogen oxides that react with water to form strong acids, that fall on the earth with rain, snow or fog (ph lower than ph 5.6) More acidic Acid rain Normal rain More basic