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Chemistry Intro

Chemistry Intro. a ncient thinkers said there must be a smallest part that stuff is made up of, this was called the atom s cientists discovered that atoms are actually made up of smaller particles Proton: Neutron: Electron:. Linked.

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Chemistry Intro

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  1. Chemistry Intro • ancient thinkers said there must be a smallest part that stuff is made up of, this was called the atom • scientists discovered that atoms are actually made up of smaller particles • Proton: • Neutron: • Electron: Linked

  2. atoms have equal number of electrons and protons so there are overall charge is zero • electrons stay around nucleus because of positive/negative attraction with protons • most of the atom is empty space where electrons move LinKed

  3. e- are found in energy levels (specific distance from nucleus) & sublevels (orbital or movement shape/pattern) • e- move in complicated patterns determined by attractive force of nucleus • to be stable (“happy”) ALL atoms want 8 e- in their outer most (valence) energy level

  4. Element - pure substance that cannot be broken down into simpler substances

  5. Practice:

  6. Periodic Table of Element • Horizontal rows gives # of energy level of electrons • Blocks give sublevel (electron orbital shapes) Linked

  7. valence – outer most energy level

  8. Isotopes • Most elements are uniform mixtures of 2 or more unique substances called isotopes. • Isotopes of an element have very similar chemical properties but their atoms have slightly different masses What about the different atoms, of the same element, could make their masses different??? _________________ __________________________________________________ __________________________________________________ Linked BrainPOP

  9. Compound is a pure substance that • is made from 2 or more different elements chemically combined • are always formed from a specific combination of elements in a fixed ratio • cannot be broken down into simpler compounds or elements by physical means.

  10. Molecules & Chemical Formulas • Atoms are identified by their elemental symbol within a formula • Subscripts tell how many atoms of that element are present in the compound/molecule i.e.) “urea” - CO(NH2)2 [from Wikipedia ”Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals”] C: 1 O: 1 N: 2 H: 4

  11. Practice How many atoms of each element are there in each formula? KHCO3 H2SO4 (NH4)2SO4 (CH3)3COH

  12. What keeps atom together to make compounds?

  13. All atoms want a full valence shell (8)

  14. Atoms with less than 4 valence will give electrons away to make 8 • Atoms with more than 4 valence will take electrons from others to make 8 • ion – atom got charged so it could get 8 valence • cation – positive charge • anion – negative charge

  15. Ionic Bonding • Oppositely charged ions attract (the attraction “glues” the ions together) and is called “ionic bond”

  16. Examples Mg N O Al

  17. shared e- “belongs” to both atoms • both valences are full • valence energy levels of overlap • the sharing/overlap binds the atoms together and is called a covalent bond What happens when neither atoms wants to give valence electrons? How can each get 8??? _______________________________________________ Linked

  18. Examples C H CH4 C2H2

  19. What about water? Formula for water ______ Water is called the universal solvent (“can dissolve a lot of stuff”)

  20. Why can water dissolve so much stuff??? dipole-dipole attraction cause water molecules to surround and isolate sugar molecules ion–dipole attraction separates NaCl formula units into isolated ions

  21. When sharing, why would one interacting thing get more than another??? ____________________________________________________________________________________________________

  22. Molecular (“Pull”) Polarity • Stronger atom PULLS electrons toward its-self • Creates area with more electrons (negative charge) • Thus, the molecule becomes partially charged • Has an area that is a little negative and another area that is a little positive water is polar (“puller”)

  23. Polarity results in ….Intermolecular (Van der Waals) Forces Dipole-Dipole - of one molecule attracts to the of another

  24. Hydrogen bonding dipole-dipole attraction of H in a polar bond to an F, O, or N in another molecule H bonding is stronger than regular dipole-dipole due to an unshared electron pair Linked

  25. Van der Waals forces of water(linked) cohesion (molecules sticking together) causes water to form drops that are nearly spherical, and adhesion ( molecules sticking to another substance) keeps the drops in place Capillary action – ability of water to flow up a thin tube without assistance against gravity

  26. Mixture -combination of two or more substances (called components) each retaining its individual identity and properties M&M’s “look” different (linked) • Heterogeneous– mixture that looks different & is different • Homogeneous – mixture that looks the same BUT is different • solution – evenly distributed homogeneous mixture • Solute – part that “does the dissolving” • Solvent – part that gets “dissolved” sugar - water - Coffee with cream & sugar looks the same

  27. Changes in Matter • Physical change – alters a substance without changing its composition • may result in drastically different appearance BUT composition of substance remains unchanged • Examples: H2O H2OH2O

  28. Acids & Bases • Acid – substance that releases H+ in water • Base – substance that releases OH- in water H+ + O H- • strength of acid/base measured by pH = -log [H+] • the more H+ the more acidic BUT the lower the pH linked

  29. Changes in Matter • What is a chemical change? • matter is neither created nor destroyed • new substance(s) are made from rearrangement of atoms • How do you know new substances have been made? • will have new physical properties

  30. Changes in Matter • Chemical change (“reaction”)– a process that involves one or more substance changing into new substances • substances formed after change have different compositions & properties from those present before • Examples: Linked

  31. Writing Chemical equations • We use formulas and symbols to describe a chemical rxn • If substance A is mixed with substance B and the two undergo a chemical change that produces substances C and D we write: A + B  C + D A and B are called the reactants (left side of arrow) C and D are called the products (right side of arrow)

  32. Balanced Chemical Equations What about the law of conservation of matter??? • Glucose and oxygen react to produce carbon dioxide and water C6H12O6 + O2  CO2 + H2O coefficient – BIG number written in front of reactant/product • tells you # of molecules tells you # of atoms

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