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chemical reaction

  1. 1. Unit 9, Chapter 29 CPO Science Foundations of Physics
  2. 2. Unit 9: The Atom <ul><li>29.1 Chemistry </li></ul><ul><li>29.2 Chemical Bonds </li></ul><ul><li>29.3 Chemical Reactions </li></ul>Chapter 29 Chemical Reactions
  3. 3. Chapter 29 Objectives <ul><li>Classify matter as substances, homogeneous or heterogeneous mixtures, or solutions. </li></ul><ul><li>Tell the difference between chemical change and physical change. </li></ul><ul><li>Describe the types of chemical bonds and the role of electrons in forming bonds between atoms. </li></ul><ul><li>Write and balance the chemical equation for a simple reaction. </li></ul><ul><li>Explain how the terms acid , base , organic , and solution relate to living systems. </li></ul><ul><li>Describe the role of photosynthesis in maintaining life on Earth. </li></ul>
  4. 4. Chapter 29 Vocabulary Terms <ul><li>substance </li></ul><ul><li>mixture </li></ul><ul><li>physical change </li></ul><ul><li>compound </li></ul><ul><li>heterogeneous mixture </li></ul><ul><li>solute </li></ul><ul><li>double bond </li></ul><ul><li>solubility </li></ul><ul><li>solvent </li></ul><ul><li>homogeneous mixture </li></ul><ul><li>dissolve </li></ul><ul><li>Solution </li></ul><ul><li>polar molecule </li></ul><ul><li>chemical bond </li></ul><ul><li>alkali metal </li></ul><ul><li>noble gas </li></ul><ul><li>element </li></ul><ul><li>valence electrons </li></ul><ul><li>transition metal </li></ul><ul><li>balanced equation </li></ul><ul><li>pH </li></ul><ul><li>covalent bond </li></ul><ul><li>amino acid </li></ul><ul><li>acid </li></ul><ul><li>organic chemistry </li></ul><ul><li>ion </li></ul><ul><li>ionic bond </li></ul><ul><li>hydrocarbon </li></ul><ul><li>protein </li></ul><ul><li>activation energy </li></ul><ul><li>products </li></ul><ul><li>reactants </li></ul><ul><li>carbohydrate </li></ul><ul><li>reaction </li></ul><ul><li>exothermic reaction </li></ul><ul><li>refine </li></ul><ul><li>octane </li></ul><ul><li>halogen </li></ul><ul><li>photosynthesis </li></ul><ul><li>endothermic reaction </li></ul><ul><li>base </li></ul><ul><li>chemical change </li></ul><ul><li>cracking </li></ul><ul><li>petroleum </li></ul><ul><li>Lewis dot diagram </li></ul><ul><li>fat </li></ul>
  5. 5. 29.1 Chemistry <ul><li>Key Question: </li></ul><ul><li>What techniques are used to separate heterogeneous mixtures? </li></ul>*Students read Section 29.1 AFTER Investigation 29.1
  6. 6. 29.1 Relationship between sciences <ul><li>Chemistry is the science of how atoms and elements create the world we experience. </li></ul><ul><li>Our world contains millions of chemicals made from the basic elements and even more interactions between chemicals. </li></ul>
  7. 7. Homogeneous mixtures MIXTURES MATTER SUBSTANCES Heterogeneous mixtures Elements Compounds
  8. 8. 29.1 Physical Changes <ul><li>The concept of temperature and changes of phase between solid, liquid, and gas are traditionally considered part of chemistry, as are the gas laws. </li></ul><ul><li>These kinds of changes in matter are called physical changes , because matter changes physical form but one substance does not change into a completely different substance. </li></ul>
  9. 9. 29.1 Chemical Changes <ul><li>Evidence of chemical change: </li></ul><ul><ul><li>bubbling (formation of gas) </li></ul></ul><ul><ul><li>turning cloudy (formation of a new solid) </li></ul></ul><ul><ul><li>temperature change (heat or light released) </li></ul></ul><ul><ul><li>color change (formation of a new solid) </li></ul></ul>
  10. 10. 29.1 Solutions <ul><li>A solution is a mixture of two or more substances that is homogeneous at the molecular level. </li></ul><ul><li>The particles in a solution exist as individual atoms, ions, or molecules. </li></ul><ul><li>A solution is a mixture of solute dissolved in a solvent . </li></ul><ul><li>Solubility describes the amount of solute that will dissolve in a given amount of solvent. </li></ul>
  11. 12. 29.1 Solutions <ul><li>Several factors affect solubility: </li></ul><ul><ul><li>chemical nature of the solvent </li></ul></ul><ul><ul><li>the volume of solute </li></ul></ul><ul><ul><li>temperature </li></ul></ul><ul><ul><li>solute particle size </li></ul></ul><ul><li>The solubility of solids in liquids usually rises with temperature. </li></ul><ul><li>Powders dissolve quickly because they have a tremendous amount of surface area exposed to the solvent. </li></ul>
  12. 13. 29.2 Chemical Bonds <ul><li>Key Question: </li></ul><ul><li>Why do atoms form chemical bonds? </li></ul>*Students read Section 29.2 AFTER Investigation 29.2
  13. 14. 29.2 Chemical Bonds <ul><li>A chemical bond forms when atoms exchange or share electrons. </li></ul><ul><li>Most of the properties of substances come from how they form chemical bonds with other substances. </li></ul>
  14. 15. 29.2 Chemical Bonds <ul><li>Electrons that make bonds are called valence electrons. </li></ul><ul><li>Not all electrons in an atom participate in making chemical bonds. </li></ul><ul><li>Only the electrons in the highest unfilled energy level make bonds. </li></ul>
  15. 16. 29.2 Chemical Bonds <ul><li>Molecules of the chemical benzene have six carbon atoms and six hydrogen atoms shaped in a ring. </li></ul><ul><li>An atom can make one chemical bond for each valence electron. </li></ul><ul><li>Bonds can also involve two or more valence electrons. </li></ul>
  16. 17. 29.2 Chemical Bonds <ul><li>Elements with the same number of valence electrons are chemically similar. </li></ul><ul><li>The same number of chemical bonds are made with the same elements. </li></ul>
  17. 18. 29.2 Chemical Bonds <ul><li>Atoms are most stable when they have either 2 or 8 valence electrons. </li></ul><ul><li>The Lewis dot diagram shows the element symbol surrounded by one to eight dots representing the valence electrons. </li></ul>
  18. 19. 29.2 Periodic Table and Valence <ul><li>The periodic table arranges elements from left to right by the number of valence electrons. </li></ul>
  19. 20. 29.2 Chemical Bonds <ul><li>Most chemical bonds fall into two categories, depending on whether the valence electrons are transferred or shared. </li></ul><ul><li>Electrons in an ionic bond are effectively transferred from one atom to another. </li></ul><ul><li>In a covalent bond the electrons are shared between atoms. </li></ul>
  20. 21. 29.2 Ionic bonds <ul><li>The ionic bonds in a salt crystal (NaCl) come from electrical attraction between: </li></ul><ul><ul><li>negative chloride ions (Cl - ) </li></ul></ul><ul><ul><li>positive sodium ions (Na + ) </li></ul></ul>
  21. 22. 29.2 Covalent bonds <ul><li>A diamond crystal is made of pure carbon connected by a strong network of covalent bonds. </li></ul><ul><li>The hardness of diamonds is due to the fact that four covalent bonds must be broken to move each carbon atom. </li></ul>
  22. 23. 29.2 pH <ul><li>When substances are dissolved in water they divide into two categories called acids and bases. </li></ul><ul><li>An acid creates a sour taste and can dissolve reactive metals like zinc. Vinegar and lemon juice are examples of acids. </li></ul><ul><li>A base creates a bitter taste and tends to feel slippery. Ammonia is an example of a base. </li></ul><ul><li>The pH is scale that measures how acidic or basic a solution is. </li></ul>
  23. 25. 29.2 Acids <ul><li>Acid molecules include ionic bonds. </li></ul><ul><li>When an acid dissolves in water, the ionic bond breaks to create two ions- one is a hydronium ion. </li></ul><ul><li>The strong chemical reactivity of the hydronium ion ( H 3 O + )is what results in the properties of acids. </li></ul>
  24. 26. 29.2 Bases <ul><li>Bases have a strong attraction for hydrogen ions (H + ). </li></ul><ul><li>When a base such as ammonia (NH 3 ) dissolves in water, the molecules of ammonia take a hydrogen ion (proton) from water molecules and become ammonium ions (NH 4 + ). </li></ul><ul><li>The pH is a measure of the concentration of H 3 O + (acid) ions in a solution. </li></ul><ul><li>The higher the pH, the stronger the base. </li></ul>
  25. 27. 29.2 Organic Chemistry <ul><li>Organic chemistry is the chemistry of carbon and its compounds. </li></ul><ul><li>The mass of your body is mostly oxygen, carbon, and hydrogen. </li></ul><ul><li>Proteins, amino acids, fats and carbohydrates are types of carbon molecules found in the body. </li></ul>
  26. 28. 29.3 Chemical Reactions <ul><li>Key Question: </li></ul><ul><li>How can you predict the yield of a chemical reaction? </li></ul>*Students read Section 29.3 AFTER Investigation 29.3
  27. 29. 29.3 Chemical Reactions <ul><li>In chemical reactions you start with reactants that are combined into products . </li></ul><ul><li>The reactants and products may include atoms , molecules , and energy. </li></ul>
  28. 30. 29.3 Chemical Reactions <ul><li>The formation of rust from oxygen and iron is an example of a common chemical reaction. </li></ul>
  29. 31. 29.3 Chemical Reactions <ul><li>Chemical reactions proceed in two stages. </li></ul><ul><li>First, the chemical bonds must be broken between the atoms in the reactants. </li></ul><ul><li>In the second stage, new bonds form between atoms to make the products of the reaction. </li></ul>
  30. 32. 29.3 Activation energy <ul><li>The energy needed to break chemical bonds in the reactants is called the activation energy of the reaction. </li></ul><ul><li>A spark supplies the activation energy to start the reaction between hydrogen and oxygen. </li></ul>
  31. 33. 29.3 Activation energy <ul><li>A chemical equation is balanced when the number of each type of atom is the same in reactants and products. </li></ul>
  32. 36. 29.3 Mass in chemical reactions <ul><li>A balanced chemical equation is like a recipe. </li></ul><ul><li>The mass of the products must equal the mass of the reactants. </li></ul><ul><li>Counting molecules is not practical so we usually need the mass of reactants and products of a chemical reaction. </li></ul>
  33. 37. 29.3 Calculating mass <ul><li>Calculate the mass of each molecule or atom. </li></ul>
  34. 38. 29.3 Calculating mass <ul><li>Use a balanced equation to calculate mass of reactants or products. </li></ul>
  35. 39. 29.3 Photosynthesis <ul><li>The energy that supports life on Earth starts with a reaction that takes energy from sunlight and stores it as chemical bonds in molecules of glucose. </li></ul><ul><li>This reaction is called photosynthesis . </li></ul>
  36. 40. 29.3 Photosynthesis <ul><li>Nearly all energy in living things can be traced to this important reaction. </li></ul><ul><li>Energy and oxygen are two useful products of photosynthesis. </li></ul>
  37. 41. 29.3 Photosynthesis <ul><li>A third crucial function of photosynthesis is to remove carbon dioxide from the atmosphere. </li></ul><ul><li>If too much carbon dioxide is present, the Earth cannot cool itself by radiating energy into space. </li></ul>
  38. 42. Application: Energy from Gasoline