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UNIT 2: Basic Chemistry

UNIT 2: Basic Chemistry. BIG IDEA: Examining substances at the molecular level helps us understand basic processes of life . Types of bonds that form Compounds. Covalent- each atom shares electrons with the other Molecules are formed by this type of bond. Types of bonds that form Compounds.

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UNIT 2: Basic Chemistry

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  1. UNIT 2: Basic Chemistry BIG IDEA: Examining substances at the molecular level helps us understand basic processes of life

  2. Types of bonds that form Compounds • Covalent- each atom shares electrons with the other • Molecules are formed by this type of bond

  3. Types of bonds that form Compounds • Ionic Bond- One atom gives an electron to the other

  4. IONIC: • Creates opposite charge that holds atoms together • Form crystals

  5. Chemical Formulas • Al2O3 • 2Al2O3 Subscript shows how many atoms of the elementit is written after This number shows how many of the entire molecule their are

  6. Chemical Reactions • Reactants: The “stuff” you start with • Products: The “stuff” you end up with A + B  C Reactants Products

  7. Chemical Reactions • Change in the arrangement of atoms that creates a different substanceNumber of atoms before and after the reaction are equal. A + B  C synthesis reaction A  B + C decomposition A + B  C + D Displacement

  8. Chemical Reactions C6H12 O6+ 6O26CO2+ 6H2O C6H12 O6 + C6H12 O6 C12H22O11 + 6H2O H20  H+ + OH-

  9. Chemical Reactions- Bonds • Compounds • Atoms are chemically bound together • Definite proportions required • Properties of a compound are different from the properties of the elements that make up that compound • Made up of many particles of the same type held together by a bond using the valence electrons

  10. Mixtures • Mixtures have “ingredients” that do not bind chemically with each other • Each ingredient keeps its own properties • Definite proportions not required • Types: solution, suspension, colloid

  11. Mixtures • Solution: homogeneous; even throughout; solute (substance) completely dissolves in solvent (liquid) examples: air, • Suspension: Heterogeneous; looks even if shaken; but particles settle to bottom examples-water column in oceans and lakes

  12. Mixtures • Colloid: heterogeneous BUT does not settle; sort of in between the other two. Examples-milk and fog

  13. Mixtures vs. Compounds Look at your notes: What are three big differences between Mixtures and Compounds?

  14. Properties of Water Water is held together with special covalent bond called polar covalent bond - Means water has poles, or ends. - O is the negative end - H’s are the positive end

  15. Water is the Universal Solvent • Important solvent in many solutions • Anything with a charge will attract water molecules and dissolve • Ionic and polar molecules have charge • Nonpolar molecules (like fat) do not have charge and will not dissolve

  16. Properties of Water

  17. Properties of Water Cohesion: Water molecules stick together because of charges

  18. Cohesion Creates Surface tension - allows stickbugs to walk on water!

  19. Adhesion Water molecules stick to other charged substances like glass Glass stirring rod

  20. Concept of pH • pH = power of Hydrogen • A way of measuring how many Hydrogen ions, H+, there are in a solution • Determines whether a solution is an acid or a base

  21. Acids and Bases • Acids: a chemical that when dissolved in water releases a hydrogen ion (H+) HX (in water)  H+ + X-

  22. Properties of Acids • Taste sour – think of lemon • Turn litmus paper from blue to red • Corrodes Metal • Examples: Sulfuric Acid, Lemon Juice, Battery Acid

  23. Acids and Bases • Base: a chemical that when dissolved in water releases a hydroxide ion (OH-) XOH (in water)  OH- + X+

  24. Properties of Bases • Taste bitter – cough meds. • Turn litmus paper back to blue after acid turns it red • Can cause serious burns • Examples: Bleach, KOH, NaOH

  25. Acids and Bases - Examples • NaOH + H2O  Na+ + OH- + H2O • HCl + H2O  H+ + Cl- + H2O

  26. Acids and Bases will “cancel” each other out • When an Acid and a Base are mixed together they will “Neutralize” each other and create Water and a Salt • This is a Neutralization Reaction

  27. Neutralization Reaction • HCl + NaOH NaCl + H2O A Salt Water • HNO3 + KOH  KNO3 +H2O A salt Water

  28. pH Scale – a measure of the concentration of Hydrogen Ions Acid Neutral (water) Base 0 1 2 3 4 7 8 9 10 11 12 13 14 5 6 High H+ Low OH- High OH- Low H+ H+ = OH-

  29. Concept of pH • Where is the “safe” pH? • pH must stay between 6.5 - 7.5 in the human body • Another factor that must maintain homeostasis

  30. Concept of pH • Are there exceptions? • Stomach is acidic • Intestines are basic • Buffers are necessary • weak acids or bases that react with strong acids or bases to prevent sudden changes in pH

  31. What is the pH of Rain water?? Usually between 5.6- 5.8 - Water reacts with CO2 in air to form Carbonic Acid (H2CO3)

  32. What is the pH of Rain water?? Acid Rain: - Rain water reacts with pollutants such as Sulphur dioxide and Nitrogen oxides in air - Forms Sulphuric Acid, Nitric Acid, Ammonium Sulphate - Decreases pH even further

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