1 / 27

Chapter 2

Chapter 2. Atoms, Molecules and Properties of Water. Matter Element 25 of the 92 elements are essential to life. Atoms. Atoms are electrically neutral An element’s properties depends on structure of its atoms Atomic number Mass number (Atomic mass).

craig
Download Presentation

Chapter 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter2 Atoms, Molecules and Properties of Water

  2. Matter • Element • 25 of the 92 elements are essential to life

  3. Atoms

  4. Atoms are electrically neutral • An element’s properties depends on structure of its atoms • Atomic number • Mass number (Atomic mass)

  5. Atoms of an element have same number of protons • Isotopes • Radioactive isotopes

  6. Energy • Potential energy • Electron shells

  7. Valence electrons • Determines chemical behavior Bohr models of atoms

  8. Most elements need 8 electrons to fill valence shell • Rule of octet • Full valence shell - inert or stable • Vacancies – reactive

  9. chemical bonds • Atoms share or transfer valence electrons • Molecules and Compounds • emergent properties

  10. Ionic Bonds • transfer of electrons • Ions • cation • anion • Salts

  11. Covalent bond • shared electrons • Single, double, triple

  12. Electronegativity • Polar vs non-polar bonds Unequal sharing of electrons causes partial charges

  13. Hydrogen Bonds • Polar covalent molecules • Positive hydrogen attracted to a negative oxygen or nitrogen • Weak and temporary

  14. Why is Water important to Life? • Life on earth probably originated in water • Water covers 75% of the earth • Living organisms are 60 - 90% water • Hydrogen bonds give water several unique properties that support life

  15. The polarity of water results in hydrogen bonds • polar molecule • Oxygen very electronegative • Attractions exist between partially charged poles Polar covalent bonds Hydrogen bonds

  16. Emergent properties of water contribute to life • Cohesive and Adhesive nature • Ability to moderate temperature • Solid form lighter than liquid form • Versatility as a solvent • Influence on pH

  17. Cohesion • Water molecules tend to stick to each other • Surface tension

  18. Adhesion • Water molecules stick to other polar molecules

  19. Moderation of Temperature • Heat is transferable energy • Objects exchange heat until they are achieve an equal temperature • Water has a high specific heat • Absorbs/releases great amounts of heat

  20. Water has a high heat of vaporization • Evaporative cooling

  21. Water Expands when it freezes • Ice floats in liquid water • Hydrogen bonds are more “ordered,” making ice less dense • Floating ice insulates bodies of water

  22. Water interacts with many other molecules • Many molecules dissolve easily in water • Solvent vs. Solute • Hydrophillic vs. Hydrophobic

  23. Water molecules can dissociate • Hydrogen ion (H+) and Hydroxide ion (OH-) • H2O H+ + OH- • The resulting ions are highly reactive! • Results in acidic and basic solutions • Measured as pH

  24. Acid • increases [H+]of a solution • Base • decreases[H+]or increases [OH-]of a solution • Salt • has no impact on [H+]of a solution

  25. [H+] is measured using a pH scale (0-14) • pH calculated by: • pH = -log [H+] • Each number represents a tenfold difference in [H+]

  26. Buffers • minimize changes in [H+] and [OH-] • Prevent large shifts in pH • pH of living cells maintained close to 7 (neutral)

  27. Blood always contains a combination of some carbonic acid and some bicarbonate ions. When [H+] in blood is too high: When [OH−] in blood is too high:

More Related