 1.What is the difference between a chemical and physical change? 2.Give an example of a chemical change and a physical change. 3.How can you tell a chemical reaction has occurred? Questions

  Physical change - deals with energy and states of matter.  Ex: Crushing a can, melting an ice cube.  Chemical change - takes place on a molecular level and a new substance is produced.  Ex: Burning, cooking an egg. Chemical vs. Physical

  Chemical Reaction – When two or more substances come together to form a new substance.  Chemical Reactions are all around us!  What are some examples of chemical reactions in your life? Chemical Reactions

  New substance  Light  Heat  Color Change  Gas  Odour  Sound How To Tell A Chemical Reaction Has Occurred

 4. What is a chemical equation? On what side of the equation are the products and reactants located? 5. Describe one chemical reaction that occurs in everyday life. Questions

  Chemical Equation – Way of representing a chemical reaction.  Ex: 2H 2 + O 2 2H 2 O  Reactants – substances being brought together to react (before reaction)  Products – substances formed (after reaction) ReactantsProducts  Reactants yield the products.  Ex: The reaction of Hydrogen and Oxygen yields Dihydrogen Monoxide (water) Reactions

  (l) = Liquid  (g) = Gas  (s) = Solid  (aq) = Aqueous Solution (solvent is water)  = Points in direction of reaction Reaction Symbols

 6. What is a diatomic element? Give an example. What is one way of remembering which elements they are? 7. What is the Law of Conservation of Mass? Questions

  Diatomic Elements are those that occur naturally as two. (Di = 2)  Ex: Hydrogen occurs as H 2 not as H.  There are 7 diatomic elements:  H 2, N 2, O 2, F 2, Cl 2, Br 2, and I 2. Diatomic Elements

  Use the acronym I Bring Clay For Our New Home:  I = Iodine  Bring = Bromine  Clay = Chlorine  For = Fluorine  Our = Oxygen  New = Nitrogen  Home = Hydrogen How to Remember Diatomic Elements

 Diatomic Elements form a 7 on the periodic table plus Hydrogen in the corner!

  Write down the following chemical reaction in words: 2 NO + O 2  2NO 2  Nitrogen Monoxide and Oxygen yield Nitrogen Dioxide Chemical Equations: In Words

  Law of Conservation of Mass – The mass of the reactants equals the mass of the products.  In other words, what goes in to the reaction, must come out! Nothing just disappears! Ex: Formation of Water H 2 (g) + O 2 (g)  H 2 O (l)  There are two hydrogens on both sides, but only two oxygens on the left and one on the right. So the equation needs to be balanced! Chemical Equations: Balancing

  In order to balance an equation (have equal number of atoms on each side), you must place coefficients (numbers) in front of the atoms or molecules. ____ H 2 (g) + ____ O 2 (g)  _____ H 2 O (l) Chemical Equations: Balancing 2 2 So now you have four hydrogens on each side and two oxygens on each side. Balanced!

  Rules:  Can’t add extra molecules or atoms into the equation!  Never change molecular formulas!  Tips:  If an element occurs as a free element, balance this element last.  Can use fractions to help in balancing, but need to clear the fractions by multiplying by a common multiplier. Balancing Equations

 8. What does it mean to be an aqueous solution? 9. What are the five different types of reactions? 10. What is a synthesis reaction? 11. What is a decomposition reaction? 12. What is a single displacement reaction? 13. What is a double displacement reaction? 14. What is a combustion reaction? Questions

  When writing down an equation, make sure to write down the states of each element and compound. Ex: Aluminum reacts with Copper (II) Chloride to form Copper metal and Aluminum Chloride. Write the balanced equation for this reaction. 2Al + 3CuCl 2  3Cu + 2AlCl 3 Chemical Equation from Words

 Types of Reactions You need to be able to identify the type of reaction and predict the product(s) 1.Synthesis 2.Decomposition 3.Single Replacement 4.Double Replacement 5.Combustion

 Steps to Writing Reactions 1.Identify the type of reaction 2.Predict the product(s) using the type of reaction as a model 3.Balance it

 Synthesis Reactions Synthesis reactions occur when two substances (generally elements) combine and form a compound. Reactant + Reactant  1 Product or A + B  AB Examples:2H 2 + O 2  2H 2 O C + O 2  CO 2

 Practice Predict the products. Write and balance the following synthesis reaction equations. Sodium metal reacts with chlorine gas 2Na (s) + Cl 2(g)  2 NaCl (s) Solid Magnesium reacts with fluorine gas Mg (s) + F 2(g)  MgF 2(s) Aluminum metal reacts with fluorine gas 2 Al (s) + 3F 2(g)  2 AlF3

 Decomposition Reactions Decomposition reactions occur when a compound breaks up into the elements or to a few simpler compounds 1 Reactant  Product + Product or In general: AB  A + B Examples: 2 H 2 O  2H 2 + O 2 2 HgO  2Hg + O 2

 Decomposition Exceptions Carbonates and chlorates are special case decomposition reactions that do not decompose into their elements. Carbonates (CO 3 2- ) decompose to carbon dioxide and a metal oxide Example: CaCO 3  CO 2 + CaO Chlorates (ClO 3 - ) decompose to oxygen gas and a metal chloride Example: 2 Al(ClO 3 ) 3  2 AlCl O 2

 Practice Predict the products. Then, write and balance the following decomposition reaction equations: Solid Lead (IV) oxide decomposes PbO 2 (s)  Aluminum nitride decomposes AlN (s)  Pb(s) + O 2 (g) 2 Al (s) + N 2 (g) 2

 Single Displacement Reactions Single Displacement Reactions occur when one element replaces another in a compound. A metal can replace a metal (+) or a nonmetal can replace a nonmetal (-). element + compound  element + compound A + BC  AC + B (if A is a metal) A + BC  BA + C (if A is a nonmetal) *Remember the cation (+) always goes first in a compound*

 Single Displacement Reactions Write and balance the following single displacement reaction equation: Zinc metal reacts with aqueous hydrochloric acid Zn (s) + 2 HCl (aq)  ZnCl 2 + H 2(g) Note: Zinc replaces the hydrogen ion in the reaction

 Single Displacement Reactions Sodium chloride solid reacts with fluorine gas 2 NaCl (s) + F 2(g)  2 NaF (s) + Cl 2(g) *Note that fluorine replaces chlorine in the compound* Aluminum metal reacts with aqueous copper (II) nitrate 2Al (s) + 3 Cu(NO 3 ) 2(aq)  3Cu + 2Al(NO 3 ) 3

 Double Displacement Reactions Double displacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound Compound + compound  compound+ compound or AB + CD  AD + CB Examples: AgNO 3(aq) + NaCl (s)  AgCl (s) + NaNO 3(aq) K 2 SO 4(aq) + Ba(NO 3 ) 2(aq)  2KNO 3(aq) + BaSO 4(s)

 Double Displacement Practice Predict the products and balance the equations. 1.HCl (aq) + AgNO 3(aq)  2.CaCl 2(aq) + Na 3 PO 4(aq)  3.Pb(NO 3 ) 2(aq) + BaCl 2(aq)  4.FeCl 3(aq) + NaOH (aq)  5.H 2 SO 4(aq) + NaOH (aq)  6.KOH (aq) + CuSO 4(aq)  HNO 3 + AgCl Ca 3 (PO 4 ) 2 + 6NaCl PbCl 2 + Ba(NO 3 ) 2 Fe(OH) 3 + 3NaCl 2H 2 O + Na 2 (SO 4 ) K 2 SO 4 + Cu(OH)

 Combustion Reactions Combustion reactions occur when a hydrocarbon reacts with oxygen gas. Also called burning! You need three things to burn something. A Fuel (hydrocarbon) Oxygen to burn it with Something to ignite the reaction (spark)

  In general: C x H y + O 2  CO 2 + H 2 O  Products in combustion are always carbon dioxide (CO 2 ) and water (H 2 O).  Incomplete burning causes byproducts such as carbon monoxide.  Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C 8 H 18 ) Combustion Reactions

 Example: C 5 H O 2  5 CO H 2 O Write the products and balance the following combustion reaction: C 10 H 22 + O 2  20 CO H 2 O 231

 15. What is an exothermic reaction? Give an example. 16. What is an endothermic reaction? Give an example. Questions

  Reactions can be classified as either Endothermic or Exothermic depending on whether it gives off energy or takes energy in.  Energy can be in the form of light or heat.  Energy Change is denoted by ∆H.  ∆H = kJ/mol Endothermic vs. Exothermic

  Exothermic Reactions are those that give off energy (light or heat).  Reactants  Products + Energy  Ex: In the formation of water 2H 2 + O 2  2H 2 O kJ  ∆H = kJ/mol  ∆H is negative in exothermic reactions because energy is given off or lost. Exothermic Reactions

  Some examples are: Exothermic Reactions

  Endothermic Reactions are those that absorb energy (heat and light).  Reactants + Energy  Products  Ex: In the melting of ice 6.00 kJ + H 2 O (s)  H 2 O (l) ∆H = kJ/mol  ∆H is positive in endothermic reactions because it is energy needed for the reaction to occur. Endothermic Reactions

  Some examples:  Melting  Baking  Cooking  Ice Packs Endothermic Reactions