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PSC 4012

PSC 4012. Ionic Phenomena: A study of an environmental problem. PSC 4012. Changes in matter can be: (Fig 3.1, page 3.4) Physical (appearance) Chemical (electrons in last shell) Nuclear (nucleus). PSC 4012. Physical changes: Superficial change Needs little amount of energy

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PSC 4012

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  1. PSC 4012 Ionic Phenomena: A study of an environmental problem

  2. PSC 4012 Changes in matter can be: (Fig 3.1, page 3.4) • Physical (appearance) • Chemical (electrons in last shell) • Nuclear (nucleus)

  3. PSC 4012 Physical changes: • Superficial change • Needs little amount of energy • DOES NOT change nature of element or compound • DOES NOT affect the properties of element or compound • Changes state of matter

  4. PSC 4012 Physical changes:

  5. PSC 4012 Nuclear changes: • Most profound change • Needs much more energy • Involves particles in nucleus! • An element is changed into another • ALL involve emission of radiation (which can be harmless, dangerous, or lethal)

  6. PSC 4012 Chemical changes (chemical reactions): • More profound change • Needs more energy • Involves electrons in last shell • NEW SUBSTANCES are formed • Evidences of chemical change: _change of color _gas release _formation of precipitate _change of temperature

  7. PSC 4012 Chemical changes: Ionization: when an atom gains or loses one or more electrons, it turns into an ion. • Thus ions become negatively charged when atoms gain electrons (A-, anion) • Or positively charged when atoms lose electrons (M+cation)

  8. PSC 4012 Classification of matter (Fig. 5.1, p 5.5): Mixtures Separation Methods: _Filtration _Decantation _Evaporation _Distillation

  9. PSC 4012 Molecules: Specific combination of atoms (same or different elements) that are united by chemical bonds Example: _H2O (Water) 1 molecule of water contains 2 elements (hydrogen and oxygen) Each element has H: 2 atoms, O: 1 atom

  10. PSC 4010: Chapter 4 Molecules: Practice Exercise Page 3.8, Ex. 3.4

  11. PSC 4012 Compounds: Pure chemical substance whose molecules are made of one or more elements (e.g. Gold, Water, Sulfuric Acid) Element: A substance made of only one type of atom. For example: Gold (Au) Binary compound: Compound made of two elements. For example: Water (H2O) Complex compound: Compound made of more than two elements. For example: Sulfuric Acid (H2SO4)

  12. PSC 4010: Chapter 4 Compounds: Practice Exercise Page 3.8, Ex. 3.5

  13. PSC 4012 Chemical bonds: The force that keeps atoms united in chemical compounds. There are three type of chemical bonds: _Ionic _Covalent _Polar covalent

  14. PSC 4012 Ionic bonds: Is the transfer of one or more electrons from one atom to another (usually from a metal to a nonmetal) • Metals (low electronegativity, tendency to lose electrons, form Cations, positively-charged ion) • Non-metal (high electronegativity, tendency to gain electrons, form Anions, negatively-charged ion)

  15. Ionic Bond Be + O Be 2+ O2- (BeO) 8P 8N 4P 5N 8P 8N 4P 5N

  16. PSC 4012 Electronegativity: Measurement of the force of attraction exerted by an atoms on the electrons it shares with another atom. Fig 3.15, page 3.45

  17. PSC 4012 Covalent bonds: Is the sharing of one or more pair of electrons between two identicalatoms (non metals). F + F F2 9P 10N 9P 10N 9P 10N 9P 10N

  18. PSC 4012 Polar covalent bond: Is the sharing of one or more pair of electrons between two different atoms (non metals). • The more electronegative atoms tend to have a stronger attraction for the electron pair (or pairs). • This difference of electronegativity causes a certain degree of polarity, and as a result, the more electronegative atom ends up carrying a slightly negative charge whereas the less electronegative atom ends up with a slightly positive charge. • Slightly charged means a fraction of the actual charge. Do not confuse with ionic bond where the transfer of electrons is complete and so is the charge of the ions or elements involved.

  19. PSC 4012 Polar covalent bond (H2O) 8P 8N 1P 0N 1P 0N H (δ+) H (δ+) O(δ-)

  20. PSC 4012

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