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Chapter 2
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Chapter 2

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  1. Chapter 2 Life’s Chemical Basis

  2. The Basics • Matter—anything that has mass and takes up space • Solid • Liquid • Gas

  3. The basics • Element—unit of matter than cannot be broken down further by ordinary chemical reactions • 92 naturally occurring elements • 98% of weight of any living thing is made up of 6 • Carbon • Hydrogen • Oxygen • Nitrogen • Phosphorous • Sulfur

  4. Building blocks • Atom—smallest indivisible unit of an element • Molecule—multiple atoms of the same element bonded together • Compound—multiple atoms of different elements bonded together

  5. Atoms • Three subatomic particles • Protons • Neutrons • Electrons

  6. Bohr model

  7. Bohr model

  8. Bohr model

  9. Electron orbits • Orbit in “shells” • K Shell—2 electrons • L Shell—8 electrons • M Shell—18 electrons

  10. Periodic chart • Atomic Number=Protons • Atomic Mass=Protons + Neutrons

  11. Periodic chart • Elements in their natural state have neutral charge • Positive charge (protons) equals negative charge (electrons)

  12. isotopes • Change in the number of neutrons • Does not affect charge • Carbon-14 • Atomic Mass = 14 (6 Protons + 8 Neutrons) • Radioisotopes in medical diagnosis

  13. ions • Change in the number of electrons • Affects charge • Anion—negative charge • More electrons than protons • Cation—positive charge • More protons than electrons

  14. bonds • Ionic • Covalent • Hydrogen

  15. Inert elements

  16. Active elements

  17. Ionic bonds • Formed between ions • Electrons transfer from one atom to another • Opposite charges attract and hold atoms • Usually inorganic (acids, bases, salts, etc.)

  18. Covalent bonds • Atoms share electrons • Happens when both have room • Usually organic (proteins, carbohydrates, etc.)

  19. Covalent vs. ionic

  20. Hydrogen bonds • Bond between covalently bonded hydrogen atom & atom in different molecule or different location. • Individually weak, but collectively strong.

  21. water • Biologically important • Makes up 70-90% of living things • Unique properties

  22. water • Polar molecule (slight positive & negative charge) • Can easily dissolve other polar molecules • Hydrophilic • Hydrophobic • “universal solvent” • Cell membranes • Temperature stabilizing • Keeps cell processes from generating too much heat • Evaporation • Ice helps insulate

  23. water • “Stick together” • Adhesion—water sticks to itself • Cohesion—water sticks to other polar molecules • Due to polarity & hydrogen bonds

  24. acidity • pH scale • 0-14 • Based on H+ & OH- molecules • Greater H+, lower the pH • Each unit is 10-fold change • going from pH 6 to 5 increases H+ by 10 times

  25. Acidity • Acids • Donates H+ • pH less than 7 • Bases • Accepts H+ • Releases OH- • pH greater than 7 • Neutrals • Release equal numbers of H+ and OH- • pH 7.0

  26. Acidity • Buffers • Biological substances that help regulate pH • Release or absorb H+ to keep pH unchanged • Ex.—Carbonic Acid, Bicarbonate regulate blood H2CO3 + OH- HCO3- + H20 HCO3- + H+ H2CO3