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Chemical Reactions
CHEMICAL REACTIONS <ul><li>a chemical change is the  transformation  of one or more substances into new substances with ne...
<ul><li>A chemical reaction is the process by which a  chemical change  happens. </li></ul><ul><li>All chemical reactions ...
<ul><li>Some chemical reactions  absorb  energy, such as in the chemical reactions that cook food. </li></ul>CHEMICAL REAC...
CHEMICAL REACTIONS <ul><li>Other chemical reactions  release  energy in the form of  heat ,  light  and/or  sound , such a...
CHEMICAL REACTIONS <ul><li>Chemical reactions happen at different  rates .  Some chemical reactions are  fast , such as wh...
<ul><li>Other chemical reactions happen  slowly , such as the formation of rust on a corroding bicycle chain. </li></ul>
<ul><li>The chemical reactions in your own  body , which are keeping you alive, are among the  fastest  chemical reactions...
<ul><li>Chemical reactions are used in many ways in daily life.  </li></ul>CHEMICAL REACTIONS
<ul><li>Scientists are constantly working to find new kinds of  chemical reactions  in order to produce new substances wit...
<ul><li>All chemical reactions involve the conversion of starting materials, called  reactants , into new substances, call...
<ul><li>The products have different  properties  than the reactants.  These new reactions may produce substances with diff...
<ul><li>For example, when a piece of solid magnesium metal is placed into a solution of hydrochloric acid, bubbles of  hyd...
<ul><li>A chemical reaction is often described by writing a  chemical equation </li></ul>CHEMICAL EQUATIONS
<ul><li>A chemical equation uses either  words  or  symbols  and formulas to describe the changes that occur during a chem...
<ul><li>For example, the chemical reaction between solid magnesium metal and hydrochloric acid is: </li></ul>CHEMICAL EQUA...
<ul><li>Notice that  hydrogen  is expressed in the formula equation as  H 2 .  Recall that pure hydrogen exists as a  diat...
<ul><li>The chemical formulas in a formula equation will often include the following: </li></ul><ul><li>the state of matte...
<ul><li>The chemical formulas in a formula equation will often include one or more  coefficients </li></ul><ul><li>A coeff...
<ul><li>For example, in the formula equation above, a coefficient of  2  is in front of the formula  HCl .  </li></ul><ul>...
<ul><li>The total mass of  reactants  and the total mass of  products  in a reaction are always the  same . </li></ul><ul>...
<ul><li>In a chemical reaction, the mass of the products always equals the mass of the reactants. </li></ul>Law of Conserv...
<ul><li>No atoms are  destroyed  and no new atoms are  produced  during a chemical reaction. </li></ul><ul><li>Instead, th...
<ul><li>The rearrangement of atoms that occurs during a chemical reaction can be illustrated using models or diagrams. </l...
<ul><li>In this equation, there are  equal  numbers of hydrogen atoms ( 4 ) and equal numbers of oxygen atoms ( 2 ) on bot...
<ul><li>When the number of each kind of atom is the  same  in the reactants and products, the equation is said to be  bala...
REACTANTS & PRODUCTS
<ul><li>A chemical reaction that is complete except for  coefficients  is called an  unbalanced  equation or  skeleton  eq...
<ul><li>To balance a chemical equation, begin by  counting  the number of  atoms  of each  element  in the skeleton equati...
<ul><li>Balance by placing  coefficients   in front of  the chemical  formulas .  </li></ul><ul><li>Never  change a  subsc...
<ul><li>Balance atoms of elements in any  complicated  looking formulas first and balance atoms of  pure elements  last.  ...
<ul><li>Hydrogen  atoms and/or  oxygen  atoms will often appear in many or all of the formulas of the reactants and produc...
<ul><li>You may be able to treat  polyatomic  ions as a  unit .  </li></ul><ul><li>ex.) if NO 3-  appears in the reactants...
<ul><li>Example 1: </li></ul><ul><li>Balance the following chemical equation: </li></ul><ul><li>AlBr 3 (s) + Cl 2 (g)    ...
<ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) + Cl 2 (g)    AlCl 3 (s) +  3 Br 2 (g) </li></ul><ul><li>Balance the nu...
<ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) + Cl 2 (g)    AlCl 3 (s) +  3 Br 2 (g) </li></ul><ul><li>The number of ...
<ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) + Cl 2 (g)     2 AlCl 3 (s) +  3 Br 2 (g) </li></ul><ul><li>Balance the...
<ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) + Cl 2 (g)     2 AlCl 3 (s) +  3 Br 2 (g) </li></ul><ul><li>The number ...
<ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) +  3 Cl 2 (g)     2 AlCl 3 (s) +  3 Br 2 (g) </li></ul><ul><li>Balance ...
<ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) +  3 Cl 2 (g)     2 AlCl 3 (s) +  3 Br 2 (g) </li></ul><ul><li>The equa...
<ul><li>Try it! </li></ul><ul><li>Balance the following chemical equations: </li></ul><ul><li>Al + F 2     AlF 3 </li></u...
<ul><li>Try it! </li></ul><ul><li>Balance the following chemical equations: </li></ul><ul><li>2 Al +  3 F 2      2 AlF 3 ...
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Chemical Reactions

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  • your presentation is awesome, can you please send this to me.. thank you so much.. ievelano@yahoo.com
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Transcript of "Chemical Reactions"

  1. 1. Chemical Reactions
  2. 2. CHEMICAL REACTIONS <ul><li>a chemical change is the transformation of one or more substances into new substances with new properties </li></ul>
  3. 3. <ul><li>A chemical reaction is the process by which a chemical change happens. </li></ul><ul><li>All chemical reactions are also accompanied by changes in energy </li></ul>CHEMICAL REACTIONS
  4. 4. <ul><li>Some chemical reactions absorb energy, such as in the chemical reactions that cook food. </li></ul>CHEMICAL REACTIONS
  5. 5. CHEMICAL REACTIONS <ul><li>Other chemical reactions release energy in the form of heat , light and/or sound , such as the burning of wood in a campfire </li></ul>
  6. 6. CHEMICAL REACTIONS <ul><li>Chemical reactions happen at different rates . Some chemical reactions are fast , such as when rocket fuel burns. </li></ul>
  7. 7. <ul><li>Other chemical reactions happen slowly , such as the formation of rust on a corroding bicycle chain. </li></ul>
  8. 8. <ul><li>The chemical reactions in your own body , which are keeping you alive, are among the fastest chemical reactions known. </li></ul>CHEMICAL REACTIONS
  9. 9. <ul><li>Chemical reactions are used in many ways in daily life. </li></ul>CHEMICAL REACTIONS
  10. 10. <ul><li>Scientists are constantly working to find new kinds of chemical reactions in order to produce new substances with useful properties . </li></ul>
  11. 11. <ul><li>All chemical reactions involve the conversion of starting materials, called reactants , into new substances, called products . </li></ul>REACTANTS & PRODUCTS
  12. 12. <ul><li>The products have different properties than the reactants. These new reactions may produce substances with different colours or states (solid, liquid, gas) </li></ul>REACTANTS & PRODUCTS
  13. 13. <ul><li>For example, when a piece of solid magnesium metal is placed into a solution of hydrochloric acid, bubbles of hydrogen are formed as well as aqueous magnesium chloride </li></ul>REACTANTS & PRODUCTS
  14. 14. <ul><li>A chemical reaction is often described by writing a chemical equation </li></ul>CHEMICAL EQUATIONS
  15. 15. <ul><li>A chemical equation uses either words or symbols and formulas to describe the changes that occur during a chemical reaction . </li></ul>CHEMICAL EQUATIONS
  16. 16. <ul><li>For example, the chemical reaction between solid magnesium metal and hydrochloric acid is: </li></ul>CHEMICAL EQUATIONS word equation: magnesium + hydrochloric acid  magnesium chloride + hydrogen formula equation: Mg(s) + 2HCl(aq)  MgCl 2 (aq) + H 2 (g)
  17. 17. <ul><li>Notice that hydrogen is expressed in the formula equation as H 2 . Recall that pure hydrogen exists as a diatomic molecule . </li></ul><ul><li>(You will need to know which elements exist as molecules when writing formula equations) </li></ul>CHEMICAL EQUATIONS word equation: magnesium + hydrochloric acid  magnesium chloride + hydrogen formula equation: Mg(s) + 2HCl(aq)  MgCl 2 (aq) + H 2 (g)
  18. 18. <ul><li>The chemical formulas in a formula equation will often include the following: </li></ul><ul><li>the state of matter of each substance </li></ul><ul><ul><li>(s) = solid </li></ul></ul><ul><ul><li>(l) = liquid </li></ul></ul><ul><ul><li>(g) = gas </li></ul></ul><ul><ul><li>(aq) = aqueous </li></ul></ul>CHEMICAL EQUATIONS
  19. 19. <ul><li>The chemical formulas in a formula equation will often include one or more coefficients </li></ul><ul><li>A coefficient is an integer that is placed in front of the symbol of an element to show the ratios of the different substances that are present in the chemical reaction </li></ul>CHEMICAL EQUATIONS
  20. 20. <ul><li>For example, in the formula equation above, a coefficient of 2 is in front of the formula HCl . </li></ul><ul><li>This means that Mg and HCl combine in a ration of 1:2 </li></ul>CHEMICAL EQUATIONS formula equation: Mg(s) + 2HCl(aq)  MgCl 2 (aq) + H 2 (g)
  21. 21. <ul><li>The total mass of reactants and the total mass of products in a reaction are always the same . </li></ul><ul><li>In other words, the mass is conserved </li></ul>CONSERVATION OF MASS
  22. 22. <ul><li>In a chemical reaction, the mass of the products always equals the mass of the reactants. </li></ul>Law of Conservation of Mass:
  23. 23. <ul><li>No atoms are destroyed and no new atoms are produced during a chemical reaction. </li></ul><ul><li>Instead, the atoms in the reactants are simply rearranged to form the products </li></ul><ul><li>Chemical bonds between atoms are broken and new ones are formed , and the atom simply reconnect in new ways </li></ul>CONSERVATION OF MASS
  24. 24. <ul><li>The rearrangement of atoms that occurs during a chemical reaction can be illustrated using models or diagrams. </li></ul><ul><li>For example : </li></ul><ul><li>word equation : hydrogen + oxygen  water </li></ul><ul><li>formula equation : 2H 2 (g) + O 2 (g)  2H 2 O(l) </li></ul>REACTANTS & PRODUCTS
  25. 25. <ul><li>In this equation, there are equal numbers of hydrogen atoms ( 4 ) and equal numbers of oxygen atoms ( 2 ) on both the reactants side and the products side. </li></ul><ul><li>formula equation : 2H 2 (g) + O 2 (g)  2H 2 O(l) </li></ul>REACTANTS & PRODUCTS
  26. 26. <ul><li>When the number of each kind of atom is the same in the reactants and products, the equation is said to be balanced . </li></ul><ul><li>formula equation : 2H 2 (g) + O 2 (g)  2H 2 O(l) </li></ul>REACTANTS & PRODUCTS
  27. 27. REACTANTS & PRODUCTS
  28. 28. <ul><li>A chemical reaction that is complete except for coefficients is called an unbalanced equation or skeleton equation. </li></ul>BALANCING CHEMICAL REACTIONS
  29. 29. <ul><li>To balance a chemical equation, begin by counting the number of atoms of each element in the skeleton equation. </li></ul>BALANCING CHEMICAL REACTIONS
  30. 30. <ul><li>Balance by placing coefficients in front of the chemical formulas . </li></ul><ul><li>Never change a subscript in a formula to help make atoms balance! </li></ul>BALANCING CHEMICAL REACTIONS
  31. 31. <ul><li>Balance atoms of elements in any complicated looking formulas first and balance atoms of pure elements last. </li></ul>BALANCING CHEMICAL REACTIONS H 2
  32. 32. <ul><li>Hydrogen atoms and/or oxygen atoms will often appear in many or all of the formulas of the reactants and products. </li></ul><ul><li>When this is the case, balance other elements first, balance hydrogen second last and oxygen last . </li></ul>BALANCING CHEMICAL REACTIONS
  33. 33. <ul><li>You may be able to treat polyatomic ions as a unit . </li></ul><ul><li>ex.) if NO 3- appears in the reactants and products of a skeleton equation, count the number of NO 3- groups rather than the number of N and O atoms separately. </li></ul>BALANCING CHEMICAL REACTIONS
  34. 34. <ul><li>Example 1: </li></ul><ul><li>Balance the following chemical equation: </li></ul><ul><li>AlBr 3 (s) + Cl 2 (g)  AlCl 3 (s) + Br 2 (g) </li></ul><ul><li>1.) Count the number of atoms in the reactants and products: </li></ul>BALANCING CHEMICAL REACTIONS
  35. 35. <ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) + Cl 2 (g)  AlCl 3 (s) + 3 Br 2 (g) </li></ul><ul><li>Balance the number of bromine atoms by adding a coefficient of 2 in front of AlBr 3 and a coefficient of 3 in front of Br 2 . Count the atoms again: </li></ul>BALANCING CHEMICAL REACTIONS
  36. 36. <ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) + Cl 2 (g)  AlCl 3 (s) + 3 Br 2 (g) </li></ul><ul><li>The number of aluminum atoms is no longer equal. </li></ul>BALANCING CHEMICAL REACTIONS
  37. 37. <ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) + Cl 2 (g)  2 AlCl 3 (s) + 3 Br 2 (g) </li></ul><ul><li>Balance the number of aluminum atoms by adding a coefficient of 2 in front of AlCl 3 . Count the atoms again: </li></ul>BALANCING CHEMICAL REACTIONS
  38. 38. <ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) + Cl 2 (g)  2 AlCl 3 (s) + 3 Br 2 (g) </li></ul><ul><li>The number of chlorine atoms is no longer balanced. </li></ul>BALANCING CHEMICAL REACTIONS
  39. 39. <ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) + 3 Cl 2 (g)  2 AlCl 3 (s) + 3 Br 2 (g) </li></ul><ul><li>Balance the number of chlorine atoms by adding a coefficient of 3 in front of Cl 2 . Count the atoms again: </li></ul>BALANCING CHEMICAL REACTIONS
  40. 40. <ul><li>Example 1: </li></ul><ul><li>2 AlBr 3 (s) + 3 Cl 2 (g)  2 AlCl 3 (s) + 3 Br 2 (g) </li></ul><ul><li>The equation is balanced! </li></ul>BALANCING CHEMICAL REACTIONS
  41. 41. <ul><li>Try it! </li></ul><ul><li>Balance the following chemical equations: </li></ul><ul><li>Al + F 2  AlF 3 </li></ul><ul><li>Ca + H 2 O  Ca(OH) 2 + H 2 </li></ul><ul><li>CaCl 2 + Na 3 PO 4  Ca 3 (PO 4 ) 2 + NaCl </li></ul>BALANCING CHEMICAL REACTIONS
  42. 42. <ul><li>Try it! </li></ul><ul><li>Balance the following chemical equations: </li></ul><ul><li>2 Al + 3 F 2  2 AlF 3 </li></ul><ul><li>Ca + 2 H 2 O  Ca(OH) 2 + H 2 </li></ul><ul><li>3 CaCl 2 + 2 Na 3 PO 4  Ca 3 (PO 4 ) 2 + 6 NaCl </li></ul>BALANCING CHEMICAL REACTIONS

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