1. Chemical Reactions

2. Questions 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?

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

4. Chemical Reactions 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?

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

6. Questions 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.

7. Reactions Chemical Equation – Way of representing a chemical reaction. – Ex: _____________________ – substances being brought together to react (before reaction) _____________________ – substances formed (after reaction) ReactantsProducts Reactants yield (produce) the products. – Ex: The reaction of Hydrogen and Oxygen yields Dihydrogen Monoxide (water)

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

9. Questions 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?

10. Diatomic Elements 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:

11. How to Remember 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

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

13. Chemical Equations: In Words Write down the following chemical reaction in words: 2 NO + O 2  2NO 2 ____________________________________________ ____________________________________________ ____________________________________________

14. Chemical Equations: Balancing Law of Conservation of Mass – The mass of the reactants _______________________________________________. 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!

15. 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) (you can use an inventory list to help you)

16. Balancing Equations 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.

17. Questions 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?

18. Chemical Equation from Words 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.

19. Types of Reactions You need to be able to identify the type of reaction and predict the product(s) 1._____________________ 2._____________________ 3._____________________ 4._____________________ 5._____________________

20. Steps to Writing Reactions 1.Identify the type of reaction 2.Predict the product(s) using the type of reaction as a model 3._____________________!!

21. Synthesis Reactions Synthesis reactions occur when two substances (generally elements) combine and form a compound. Reactant + Reactant  1 Product or Examples:

22. Practice Predict the products. Write and balance the following synthesis reaction equations. Sodium metal reacts with chlorine gas Solid Magnesium reacts with fluorine gas Aluminum metal reacts with fluorine gas

23. Decomposition Reactions Decomposition reactions occur when a compound breaks up into the elements or to a few simpler compounds 1 Reactant  Product + Product or Examples:

24. 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: Chlorates (ClO 3 - ) decompose to oxygen gas and a metal chloride Example:

25. 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)  2

26. 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 (if A is a metal) (if A is a nonmetal) *Remember the cation (+) always goes first in a compound*

27. Single Displacement Reactions Write and balance the following single displacement reaction equation: Zinc metal reacts with aqueous hydrochloric acid Note: Zinc replaces the hydrogen ion in the reaction

28. Single Displacement Reactions Sodium chloride solid reacts with fluorine gas *Note that fluorine replaces chlorine in the compound* Aluminum metal reacts with aqueous copper (II) nitrate

29. 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 Examples:

30. 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) 

31. Combustion Reactions Combustion reactions occur when a hydrocarbon reacts with oxygen gas. Also called burning! You need three things to burn something:

32. Combustion Reactions In general: 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 )

33. Combustion Reactions Example: Write the products and balance the following combustion reaction: C 10 H 22 + O 2 

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

35. Endothermic vs. Exothermic 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

36. Exothermic Reactions 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 + 483.6 kJ ∆H = - 483.6 kJ/mol ∆H is negative in exothermic reactions because energy is given off or lost.

37. Exothermic Reactions Some examples are:

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

39. Endothermic Reactions Some examples: – Melting – Baking – Cooking – Ice Packs