1. Chemical Reactions: The Basics

2. Chemical Reactions Introduction What is a chemical reaction? What is a chemical reaction? Any process in which one set of substances is converted into a new set of substances Any process in which one set of substances is converted into a new set of substances Any process in which a chemical change occurs Any process in which a chemical change occurs Indicators of a chemical reaction are the exact same as those of a chemical change: Indicators of a chemical reaction are the exact same as those of a chemical change: 1. Color Change 2. Heat or light is given off 3. Gas is released 4. A solid precipitate is formed in a liquid 5. The change is difficult or impossible to reverse

3. Chemical Reactions: Components Each chemical reaction has two main components: reactants & products Each chemical reaction has two main components: reactants & products 1. Reactants: 1. Reactants: What you start with before the reaction What you start with before the reaction Can be one or more substances Can be one or more substances Initial substance (s) that change in the reaction Initial substance (s) that change in the reaction I.e. – Potassium chlorate and sugar (gummy bear) I.e. – Potassium chlorate and sugar (gummy bear)

4. Chemical Reactions: Components 2. Products: 2. Products: What you finish with after the reaction What you finish with after the reaction Can be one or more substances Can be one or more substances New substance (s) that remain after the reactants change New substance (s) that remain after the reactants change I.e. – Oxgyen gas & carbon ashes I.e. – Oxgyen gas & carbon ashes

5. What has to happen for a chemical reaction to occur? Chemical reactions typically do not occur at random Chemical reactions typically do not occur at random “Spontaneous” reactions are very rare: “Spontaneous” reactions are very rare: Rusting of automobiles Rusting of automobiles Most chemical reactions require some specific conditions in order to occur. These include: Most chemical reactions require some specific conditions in order to occur. These include: Adding heat Adding heat Adding water or another liquid solution Adding water or another liquid solution Breaking reactants into smaller pieces Breaking reactants into smaller pieces Mechanically stirring or mixing of reactants Mechanically stirring or mixing of reactants

6. Reaction Conditions

7. How are chemical reactions represented? Chemical reactions can be represented in various ways: Chemical reactions can be represented in various ways: Sentences: Sentences: Use complete sentences to represent the reaction; reactants and products are not specifically given Use complete sentences to represent the reaction; reactants and products are not specifically given i.e.: Magnesium ribbon combines with oxygen when burned to produce magnesium oxide i.e.: Magnesium ribbon combines with oxygen when burned to produce magnesium oxide Word equations: Word equations: Use words to illustrate the reactants and products Use words to illustrate the reactants and products i.e.: Magnesium + oxygen  magnesium oxide i.e.: Magnesium + oxygen  magnesium oxide

8. How are chemical reactions represented? Skeleton chemical equations: Skeleton chemical equations: Use chemical formulas to illustrate the reactants and products Use chemical formulas to illustrate the reactants and products The equation is not balanced The equation is not balanced i.e.: Mg + O 2  MgO i.e.: Mg + O 2  MgO Balanced chemical equations: Balanced chemical equations: Formulas are used to represent the reactants and products Formulas are used to represent the reactants and products Integers are placed in FRONT of the formulas to BALANCE the equation Integers are placed in FRONT of the formulas to BALANCE the equation i.e.: 2Mg + O 2  2MgO i.e.: 2Mg + O 2  2MgO

9. How to create word equations Read the sentence reaction Read the sentence reaction i.e.: When sodium hydroxide reacts with sulfuric acid, sodium sulfate and water are formed. i.e.: When sodium hydroxide reacts with sulfuric acid, sodium sulfate and water are formed. Determine what chemicals are used Determine what chemicals are used i.e.: sodium hydroxide, sulfuric acid, sodium sulfate, water i.e.: sodium hydroxide, sulfuric acid, sodium sulfate, water Determine which chemicals are the reactants and which chemicals are the products Determine which chemicals are the reactants and which chemicals are the products i.e.: reactants: sodium hydroxide, sulfuric acid; products: sodium sulfate, water i.e.: reactants: sodium hydroxide, sulfuric acid; products: sodium sulfate, water Write the each of the reactants on the left hand side of the equation. “Add” them together by placing a (+) in between them Write the each of the reactants on the left hand side of the equation. “Add” them together by placing a (+) in between them i.e.: sodium hydroxide + sulfuric acid i.e.: sodium hydroxide + sulfuric acid Draw an arrow pointing left towards the products (  ) Draw an arrow pointing left towards the products (  ) i.e.: sodium hydroxide + sulfuric acid  i.e.: sodium hydroxide + sulfuric acid  Write each of the products on the right hand side of the equation. “Add” them together by placing a (+) in between them Write each of the products on the right hand side of the equation. “Add” them together by placing a (+) in between them i.e.: sodium hydroxide + sulfuric acid  sodium sulfate + water i.e.: sodium hydroxide + sulfuric acid  sodium sulfate + water

10. How to create skeleton equations Determine the word equation first: Determine the word equation first: i.e.: sodium hydroxide + sulfuric acid  sodium sulfate + water i.e.: sodium hydroxide + sulfuric acid  sodium sulfate + water Determine the chemical formulas for each of the reactants and products involved: Determine the chemical formulas for each of the reactants and products involved: i.e.: Na(OH) + H 2 (SO 4 )  Na 2 (SO 4 ) + H 2 0 i.e.: Na(OH) + H 2 (SO 4 )  Na 2 (SO 4 ) + H 2 0

11. Diatomic Elements Prefix “di” = 2 Prefix “di” = 2 Elements that are ALWAYS found in pairs when they are not bonded to different atoms Elements that are ALWAYS found in pairs when they are not bonded to different atoms They are always bonded to each other covalently They are always bonded to each other covalently They become diatomic molecules They become diatomic molecules Easy to remember: SEVEN! Easy to remember: SEVEN! There are 7 diatomic elements There are 7 diatomic elements Hydrogen (H 2 ), Nitrogen (N 2 ), Oxygen (O 2 ), Fluorine (F 2 ), Chlorine (Cl 2 ), Bromine (Br 2 ) and Iodine (I 2 ) Hydrogen (H 2 ), Nitrogen (N 2 ), Oxygen (O 2 ), Fluorine (F 2 ), Chlorine (Cl 2 ), Bromine (Br 2 ) and Iodine (I 2 ) Start at atomic # 7 (nitrogen) and trace a 7 on the periodic table Start at atomic # 7 (nitrogen) and trace a 7 on the periodic table Make sure to include hydrogen Make sure to include hydrogen When found “alone”, Hydrogen is always found as H 2, Oxygen is always found as O 2, etc. When found “alone”, Hydrogen is always found as H 2, Oxygen is always found as O 2, etc. When you are writing down skeleton or balanced equations and a diatomic is involved, you must remember to include both of them! When you are writing down skeleton or balanced equations and a diatomic is involved, you must remember to include both of them!