1. Chapter 4.1 Chemical Reactions

2. Chemical Change – the transformation of one or more substances into different substances with different properties

3. Demonstrations Lycopodium + oxygen in the presence of heat Iron (III) chloride (0.2M)+ Sodium hydroxide (1M) Lead (II) nitrate + potassium iodide Magnesium metal + hydrochloric acid (1M) also try hydrogen gas test Urea + water

4. Clues to a chemical change Change in colour Energy is released or absorbed Gas is produced A precipitate (solid) forms from two liquids Difficult to reverse NOTE: a change in state or dissolving a substance is NOT a chemical change

5. How can we speed up a reaction? http://www.youtube.com/watch ?v=OttRV5ykP7A&sns=em In order for a reaction to occur, reactants must collide in the correct orientation and with the correct amount of energy

6. Methods of increasing speed 1. Decrease the volume of the reaction vessel 2. Increasing concentration 3. Increase temperature 4. Increase surface area 5. Add a catalyst (this decreases the amount of energy needed for a reaction to occur but doesn’t get consumed in the reaction) increases the number of collisions

7. Chemical Equations Represent chemical reactions by using words or symbols and formulas Starting materials are called “reactants” New substances are called “products” An arrrow (  ) is read as “produces” States of matter appear in brackets (s)=solid (l)=liquid (g)=gas (aq) dissolved in water

8. Word Equations Use words to represent reactions Use all of your naming rules to do this! Ex. Magnesium + Hydrochloric acid  Magnesium chloride + Hydrogen gas Copper (II) sulfate + Ammonium chloride  Copper (II) chloride + Ammonium sulfate Sodium metal + oxygen gas  sodium oxide

9. Skeleton Equation An unbalanced equation that shows all reactants and products in a chemical reaction written as formulas Rules: -write the symbol of a metal element that is NOT in a compound ex. “Iron Nail” is Fe

10. Skeleton Equations -If the non-metal is part of Hockey stick and puck, write it as a diatomic molecule H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 Ex. Oxygen gas reacts with fluorine gas O 2 + F 2 - Write the formula of any other compound using the rules you have learned

11. Law of Conservation of Mass States that in a chemical reaction, the mass of the products ALWAYS EQUALS the mass of the reactants since elements cannot be created or destroyed in a chemical reaction, they can only be rearranged!

12. Formula Equations Notice states of matter are always included Coefficients are used to show the ratios of the different substances present in the reaction (follows the law of conservation of mass) Ex. Mg (s) + 2HCl (aq)  MgCl 2 (aq) + H 2 (g)

13. Balancing Balance polyatomic ions first if the same ion appears on both sides of the equation Balance all other elements except H and O Balance H Balance O

14. Examples Balance the following chemical equations. 1. Fe + H 2 S0 4  Fe 2 (SO 4 ) 3 + H 2 2. C 2 H 6 + O 2  H 2 O + CO 2 3. KOH + H 3 PO 4  K 3 PO 4 + H 2 O 4. SnO 2 + H 2  Sn + H 2 O

15. Homework p. 155 #3,5 worksheet