Rates of Reactions Types of Reactions Balancing Equations

Rates of Reactions Types of Reactions Balancing Equations Chemical Reactions Covalent Bonds Ionic Bonding Review NOTES

Chemical Bonding � A chemical bond is when two or more atoms or ions are strongly attached to each other. � Ionic Bond – electrostatic force holding oppositely charged ions together � Covalent Bond – the sharing of electrons between two atoms to hold them together � Metallic Bond – a bond found amongst metals where there is a ‘sea’ of metal ions amid freely floating electrons.

Chemical Bonding � Ionic Bond – generally between metals and nonmetals � Covalent Bond – generally between nonmetals and nonmetals � Metallic Bond – formed between metals and metals

Ionic Bonding Review � Ion – a charged particle �Atoms can become charged when they gain or lose electrons. ○ Gain electrons = more negatively charged ○ Lose electrons = more positively charged � Oppositely charged particles are attracted to each other

Periodic Table Shortcuts P. Table 1 Group # 2 3 4 5 6 7 8 Valence 1 Electrons 2 3 4 5 6 7 8 Ion +1 +2 Formed +4 +3 -3 -2 -1 NA -4

Gainers and Losers � You can think about different atoms based on how many electrons they will gain or lose. � Gainers – Elements who need to gain electrons to become happy/stable. �Elements in Groups: � Losers – Elements who lose electrons to become stable. �Elements in Groups:

Compounds – opposites attract! � Positive Ions will attract Negative Ions. � A +1 ion will equally bond with a -1 ion. � A +2 ion will equally bond with a -2 ion. � What happens when a +2 ion encounters a -1 ion? � Gainers and Losers Bond together to form ionic compounds

Formation of Ionic Bond

Covalent Bonds

Covalent Bonding? � Timmy and Suzy are at their grandma’s house and they both have an 8 pack of colored pencils. Timmy is missing his red pencil and Suzy is missing her green pencil. How can they finish their pictures without a full set of their own colored pencils?

Formation of Covalent Bond � Covalent bonding �The mutual attraction and repulsion forces between the protons (+) and electrons (-) hold two atoms together. - +

Reading Covalent Bonds � For each atom, there needs to be an EDD � Each line always represents TWO SHARED electrons �This means that BOTH atoms can count them when determining if they are stable/happy. � Each dot that represents a valence electron

Reading Covalent Bonds _ Br Br 1. 2. 3. 4. 5. 6. 7. The chemical formula is _____. The type of bond is (IONIC or COVALENT). Each bond contains _____electrons. How many electrons are being SHARED total? ____ How many electrons are NOT being shared? ______ How many bonds are between Br and Br? ______ Yes or No: Are each of the atoms happy? (Circle the electrons/bonds if it helps you).

Steps for making Covalent Bonds Figure out how many atoms of each element you need. [Normally given by the formula] Draw the electron dot diagram for each of the atoms separately. 2. Decide how many electrons each atom wants to GAIN to have a full outer energy level! 3. Line up the electrons to get ready to share. 4. For each two electrons that will be shared, replace the dots with a bond (a line). Continue until each is atom “happy” when you count shared any remaining valence electrons. 1.

O N O O

O O

Chemical Reactions

Vocabulary Review � Physical Change – A change in size, shape, or state of an object, yet does not change the actual object. � Chemical Change – A change from one substance into another with different properties. Evidence includes: changes in color, odor, size, or energy either received or given off.

Vocabulary Chemical Reaction – A process of chemical change occurring when compounds change bonds and creating new, different substances. � Chemical Equation – the explanation of a chemical reaction using symbols and numbers to show the atoms involved. � Reactants – Substances that exist before a reaction. � Products – Substances that are formed from a reaction. �

Understanding Chemical Equations The point of a formula is to sum up and quickly explain a reaction that would otherwise be too long winded. The reactants of one molecule of methane and two oxygen molecules produces the products of one carbon dioxide molecule and two molecules of dihydrogen monoxide. produces CH 4 + O 2 CO 2 + H 2 O Reactants Products

Understanding Chemical Equations CH 4 + O 2 CO 2 + H 2 O Reactants Products is the same equation as 1 CH 4 + 2 O 2 1 CO 2 + 2 H 2 O is the same equation as CH 4 + 2 O 2 CO 2 + 2 H 2 O

Counting Atoms in Reactions CH 4 + 2 O 2 CO 2 + 2 H 20 Reactant Side 1 4 4 Atom Product Side Carbon 1 Hydrogen 4 Oxygen 2 + 2 = 4

6) Are atoms created or destroyed in a chemical reaction? How do you know? Atoms are not created or destroyed. There is exactly the same number of each type of atom in the products as there are in the reactants. What does the picture on the right represent? The products “balance” the reactants. There are exactly the same number of reactant atoms as there are product atoms. Furthermore, the mass on the left equals the mass on the right.

7) In a physical change, like changing state from a solid to a liquid, the substance itself doesn’t really change. Explain how is a chemical change different from a physical change? In a chemical change a new substance with different properties is formed, but in a physical change it only changes size, shape, or state.

More Counting Atoms C 3 H 8 + 5 O 2 3 CO 2 + 4 H 2 O Reactant Side 3 8 10 Atom Carbon Hydrogen Oxygen Product Side 3 8 6+4= 10

1 C 4 H 10 + 13 O 2 8 CO 2 + 10 H 2 O Reactant Side 4 10 26 Atom Carbon Hydrogen Oxygen Product Side 8 20 16 + 10 = 26 When Balancing… YOU CAN NEVER CHANGE THE NUMBER IN THE SUBSCRIPTS. ONLY COEFFICIENTS

Conservation of Mass � When a chemical reaction happens, no atoms are created or destroyed. � The number of atoms in the reactants ALWAYS EQUALS the number of atoms in the products. � For a chemical equation to be correct, the equation must be balanced.

Visualizing Equations!

Visualizing Equations CH 4 + O 2 CO 2 + H 2 O H H C H O O Not a Real Reaction H CH 4 + O 2 ? CO 2 + H 2 O

Visualizing Equations CH 4 +2 O 2 CO 2 + 2 H 2 O H H C H O O Combustion H CH 4 + 2 O 2 CO 2 + 2 H 2 O

Visualizing Equations H 2 + O 2 H 2 O H O H 2 + O 2 H 2 O? Not a Real Reaction

Visualizing Equations 2 H 2 + O 2 2 H 2 O H H O 2 H 2 + 1 O 2 2 H 2 O Synthesis 2 H 2 + O 2 2 H 2 O

Visualizing Equations Not a real reaction NH 3 N 2 + H 2 H N H H NH 3 ? N 2 + ? H 2

Visualizing Equations 2 NH 3 N 2 + 3 H 2 H H H N N H 2 NH 3 H Decomposition H N 2 + 3 H 2

Visualizing Equations H H O O Single Replacement Zn + H 2 SO 4 + Zn. SO 4 + H 2 S Zn O Zn + H 2 SO 4 O Zn. SO 4 + H 2

Visualizing Equations K S K H B r K 2 S + HBr Not a real Reaction K 2 S + HBr KBr + H 2 S ? KBr + ? H 2 S

Visualizing Equations K S K H H B r K 2 S + 2 HBr Double Replacement K 2 S + 2 HBr 2 KBr + H 2 S

Visualizing Equations HCl + Na. OH Na. Cl + H 2 O H Cl Acid Base Na HCl + Na. OH O H Na. Cl + H 2 O

Balancing Equations ○ More worked examples are found on the teacher website.

Worked Examples N 2 + H 2 NH 3 N H KCl. O 3 KCl + O 2 K Cl O

Worked Examples Na. Cl + F 2 Na. F + Cl 2 Na Cl F H 2 + O 2 H 2 O H O

What is a chemical change? A chemical change is when a new substance with different properties is formed from the reaction of the REACTANTS.

Types of Reactions 1. Synthesis: (Building something) A+B AB Example 2 H 2 + O 2 2 H 2 O 2. End with 1 Product Decomposition: (Destroying something) AB A +B Example 2 NH 3 N 2 + 3 H 2 Begin with 1 Reactant

Types of Reactions 3. Single Replacement: AX + B A + BX Example 2 K + Mg. Br 2 2 KBr + Mg Switch one partner 4. Double Replacement: AX + BY AY + BX Example 2 Al. Br 3+ 3 K 2 SO 4 6 KBr + Al 2(SO 4)3 Switch both Partners

Types of Reactions 5. Acid Base: Make a Salt and Water AOH + HB AB + H 2 O Example – Na. OH + HCl Na. Cl + H 2 O 6. Combustion: Make CO 2 and Water Cx. Hy + O 2 CO 2 + H 2 O Example – CH 4 + 2 O 2 CO 2 + 2 H 2 O

Visualizing Equations H H O 2 H 2 + 1 O 2 2 H 2 O

Visualizing Equations H H O 4 H 2 + 2 O 2 4 H 2 O

Visualizing Equations H H O H H O 6 H 2 + 3 O 2 6 H 2 O

Limiting Reactants H H O H H 6 H 2 + 2 O 2 4 H 2 O + 2 H 2

Limiting Reactants H H O H H H H 6 H 2 + 1 O 2 2 H 2 O + 4 H 2

H O H C C H O H H Na O C O O 1 Na. C 2 H 3 O 2 + 1 CO 2 + 1 H 2 O 1 C 2 H 2 O 2 + 1 Na. HCO 3

Heat Reactions � Exothermic – in these types of chemical reactions, heat is given off in the process. �Example: Burning – Substance combines with Oxygen to form heat, Light, CO 2 or Water. (Combustion) �Temperature of products rises. � Endothermic – in these types of chemical reactions, heat is absorbed in the process. �Example: A cold pack that dissolves a solution in water takes in heat from surrounding environment. �Temperature of products lowers.

� Exothermic – Reaction in which heat energy is released. �“Exo” means outside. Energy is released to the “outside. ” �Example: Burning – Substance combines with Oxygen to form heat, Light, CO 2 or Water. (Combustion) �The Energy of products is lower than reactants, but the temperature of products is higher than reactants (with the excess heat generated)

Exothermic Reaction -Releases energy -Energy of products is lower than reactants. Reaction Progress

� Endothermic – Reaction in which heat energy is absorbed. �“Endo” means “in. ” Energy goes IN to the reaction. �Example: A cold pack that dissolves a solution in water takes in heat from surrounding environment. �The Energy of products is higher than reactants, but the temperature of the reactants is lower due to the absorbed energy.

Endothermic Reaction -Absorbs energy -Energy of products is higher than reactants. Reaction Progress

Energy Exo or endo? Reaction Progress

Putting it all together! Remember Types of Reactions? � S = Synthesis: � D = Decomposition: � SR = Single Replacement: BX � DR = Double replacement: AY + BX � C= Combustion CO 2 + H 2 O A + B AB AB A + B AX + B A + AX + BY Cx. Hy + O 2

Exo or Endo? 3 CO 2 + 4 H 2 OWhat “type” of reaction is this? Energy combustion C 3 H 8 + 5 O 2 Reaction Progress

Exo or Endo? 2 H 2 O What “type” of reaction is this? Energy synthesis 2 H 2 + O 2 Reaction Progress

Exo or Endo? 2 Al. Br 3+3 K 2 SO 4 What “type” of reaction is this? 6 KBr + Al 2(SO 4 Double )3 replacement Reaction Progress

Exo or Endo? 2 Na. Cl + F 2 What “type” of reaction is this? 2 Na. F + Cl 2 Reaction Progress Single replacement

Exo or Endo? 2 KCl + 3 O 2 What “type” of reaction is this? Energy decomposition 2 KCl. O 3 Reaction Progress

Rates of Reactions � Temperature – When temperature is increases, molecular speed is increased, making reactions happen faster. If you slow down the speed (decrease temperature) then the reaction slows down as well. � Temperature Up = Reaction Rate Up � Concentration – The amount of substance in a given amount of volume. The higher the concentration, the faster the reaction because the molecules are closer together. � Concentration Up = Reaction Rate Up � Surface Area – the amount of the substance that is exposed increases the reaction rate because only outer molecules can actually react. � Surface Area Up = Reaction Rate Up

� Activation Energy – The minimum amount of energy needed to start a reaction. � Inhibitor – Slows down reactions. �Chemicals on cereal boxes slowing down the spoiling of foods. � Catalyst – speeds up reactions without being used up in the process. � Enzymes – Proteins that speed up reaction in your body

� Activation Energy – The amount of energy needed to start a reaction. The “hill” in the diagrams. You have to climb the hill before the reaction can start. � Catalyst – Speeds up reactions without being used up or changed in the process. Lowers the activation energy of a reaction. It lowers the hill! (Analogy: Like a matchmaker setting up a couple. )

A catalyst lowers the Activation Energy (the hill!) �c Would you rather be a catalyzed or uncatalyzed reaction? Which do you think occurs more easily? Is this exo or endothermic?

Catalysts you have heard about! � Enzymes = Your body’s catalysts! �Ex. Enzymes in your saliva help food be broken down FAST!

� Can a person act like a catalyst? A “catalyst” is a person who gets something started or speeds something up (MLK’s speech, starting a club, a starting a winning streak on a sports team, etc).