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The Chemistry of Life: Atoms, Compounds, and Water

Explore the nature of matter, the structure of atoms, and the formation of compounds. Discover the unique properties of water and its role in chemical reactions.

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The Chemistry of Life: Atoms, Compounds, and Water

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  1. Chapter 2 The Chemistry of Life

  2. Section 2-1: The Nature of Matter Atom – Greek “atomos” – indivisible. Named by Democritus The basic unit of all matter Made up of subatomic particles:

  3. Periodic Table of Elements Table that lists all the names & important information of elements • Element – A pure substance consisting of only 1 kind of atom • Know the elements given to you and their symbol Atomic Number = the # of Protons (= the # of electrons) Atomic Mass = the # of Protons + the # of Neutrons 6 C 12 Atomic number Atomic Mass

  4. *All atoms are electrically neutral so the # of Protons must = the # of Electrons

  5. Figure out the following elements 16O81H114N723Na1135Cl17 # Protons # Electrons # Neutrons

  6. Bohr Model of the Atom Has electrons orbiting the nucleus in a set pattern • Protons and Neutrons are in the nucleus • Electrons orbit the nucleus in orbitals or energy levels • 1st orbital gets a max of 2 electrons • 2nd and 3rd orbitals gets 8 electrons Nitrogen

  7. Make Bohr models for the 6 elements below C H O N Na Cl

  8. 24Mg 1239K19 32S1628Si14

  9. Isotopes Elements with the same atomic number but different atomic masses (# of neutrons). 12C614C616 O818O8

  10. Radioactive Isotopes Are used to follow chemical pathways as markers or for medicinal purposes in the treatment of cancer. Also used as radioactive tracers

  11. How do elements come together? Compounds - “Compere” to come together - a substance made up of 2 or more elements in definite proportions Ie. H2O, CH4, C6H12O6, NaCl *The compound will have different chemical and physical properties from the elements that it is composed of ie. NaCl +

  12. Chemical Bonding Na11 Cl17 • Ionic bonds – transfer electrons between elements

  13. Since Na has 1 “spare” electron in its outer energy level and Cl needs 1 more electron to fill its outer energy level, Na will transfer 1 electron to Cl’s outer energy level. This is Ionic bonding What results is Na+Cl-. • Na lost 1 electron so it has 1 extra positive charge – forms a + ion. • Cl gained an electron so it has 1 extra negative charge – forms a – ion • Ions – are charged particles that result from ionic bonding

  14. Na+Cl-

  15. Try Magnesium and Sulfur Mg12 S16

  16. Covalent Bonding H1 O8 Results when atoms share a pair of electrons. The outer energy level will therefore be filled for both atoms involved These are the strongest of bonds needing high energy to break them or enzymes (to be discussed later) In the case of water, both H’s shared electrons with the oxygen

  17. Do CH4 (Methane) & HCl (Hydrogen Chloride)

  18. Chemical Formulas CH4 NH3 H2O Bohr Models Structural/Molecular Diagrams

  19. Lewis Electron Dot Configuration C6 N7 Ne10 F9 B5 H1

  20. Using the model kits, make the following: O– Blue – 2 C – Black – 4 N– Red – 3 H – White – 1 Cl – White – 1 Si – Black – 4 Tubes – Covalent Bonds • H2O • O2 • CH4 • HCl • O3 • CO2 • H2 • SiO2 • C2H6 • C2H4 • C2H2 • C3H8 • NH3 Ethane Ethylene Acetylene Propane Ammonia Draw Structural Diagrams of Each

  21. Molecule Smallest unit of a compound. • H2O (1 molecule of water) • 2H2O (2 molecules) • C6H12O6 (1 molecule of glucose) • 3C6H12O6 (3 molecules of glucose)

  22. Section 2-2: Water! 65% of you is made up of water! + Hydrogen Hydrogen Oxygen - Water is a polar molecule – the Oxygen side of it has a more negative pull than … - the Positive pull of Hydrogen

  23. Because of this polarity, when something (like Na+Cl-) that is bonded ionically is placed in solution with water, it Dissociates (the ions separate). • The positive ions will be attracted to the negative side of water (the oxygen side) and the negative ion will be attracted to the positive side of water (the hydrogen side). • This makes water the Universal solvent. • Therefore, ionic bonds are weak bonds

  24. Dissociation of Salt in Water

  25. Hydrogen Bonding • Since water is polar, the Hydrogen side(+) of the molecule will be attracted to the negative side of water (oxygen side). • This special type of attraction is called H-bonding • and is a very weak bond.

  26. Other attractive forces • Cohesion – like molecules being attracted to each other. As with water droplets

  27. Adhesion – unlike molecules being attracted to each other. As in water being attracted to the glass of a graduated cylinder forming the meniscus

  28. Capillarity – a combination of the two results in a liquid being moved through a very thin tube. Upward force. Greater in smaller tubes than in larger tubes. Like using a small straw to pull up a liquid versus a fat straw.

  29. Mixtures and Solutions • Mixtures – composed of 2 or more compounds or elements that are physically mixed together. Your blood cells in plasma. Salt and pepper together in a shaker Iron fillings and salt

  30. Solution demonstration • Solutions • A mixture made by ionically bonded compounds dissociating in water • Solute – compound that is dissolved in a solution with water. • Na+ Cl- • Solvent- The substance in which the solute is dissolved in. • Water

  31. Water may react to form ions (even though it is bonded covalently) due to its polarity. H2O H+ + OH- • H+ = Hydrogen ion • OH- = Hydroxide ion

  32. If the number of H+ ions in a solution is = to the # of OH- ions, the solution is neutral If the H+ ions are > the OH- ions, then the solution is an acid If the OH- ions are > the H+ ions, then the solution is a base or alkaline.

  33. The pH scale • is a measurement of the concentration of H+ ions to OH- ions. • Each step on the scale represents a 10 fold change. Acidic NeutralAlkaline 01 2 3 4 5 678 9 10 11 12 1314 Do pH lab

  34. pH • Scale from 0 – 14 to show how acidic or alkaline a solution is • Logarithmic scale • (10 fold >/< for each step)

  35. Activity • Using universal pH paper, determine the pH of the following solutions • Dip the tip of the pH paper into the solution, wait a minute and compare it to the colored scale on the vial • List the pH’s of the following solutions: • ammonia • vinegar • milk • black coffee • baking soda solution • cola • Milk of Magnesia • lemon juice • Water • Draino • On a blank pH scale, place the solutions in the proper spot

  36. pH lab data table Ie. For a pH of 8, it has 10 x OH-

  37. Buffers – pH of most cells’ fluid is 6.5 – 7. Needs to maintain homeostasis To do this, buffers are weak acids (carbonic acid in blood) or bases that will act to prevent sharp changes in pH. Neutralization – occurs when opposites on the pH scale are added together to create water and a salt. Antacids H+Cl- + Na+OH-Na+Cl- + H2O ReactantsProducts Neutralization lab

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