Presentation on theme: "1 – Nature of Chemical Reactions 4 – Reaction Rates and Equilibrium"— Presentation transcript:
11 – Nature of Chemical Reactions 4 – Reaction Rates and Equilibrium 2 – Chemical Equations3 - Reaction Types4 – Reaction Rates and Equilibrium
2State StandardsCLE – Apply the Laws of Conservation of Mass/Energy to balance chemical equationsCLE.3202.Inq.4 – Apply qualitative and quantitative measures to analyze data and draw conclusions that are free of biasCLE.3202.Inq.6 – Communicate and defend scientific findings
31 - Nature of Chemical Reactions Key Questions :When do chemical reactions take place?What is the role of energy in chemical reactions?
4Chemical Reactions Everyday occurrences are reactions ( rxns ) Growing, ripen, decay, burnChemical reactions stem from chemical changesHow do you tell that a chemical change happens?
5Chemical Reactions Atoms are rearranged ( to form new substance ) Reactant – substance participating in rxnProduct – substance being formed by rxn
6Demonstration Add vinegar ( acetic acid ) to baking soda CO2 is producedWhat evidence of a reaction is obsered?
7Energy & Chemical Reactions Energy factors into the state of matterEnergy also plays a role in changes of stateChemical changes use energy alsoSame for chemical rxns
8Chemical Reactions Involve changes in energy ALWAYS Energy is required to break bondsForming bonds releases energy
9Chemical Reactions Energy is conserved in rxns Exothermic – Rxns that release energyEndothermic – Rxns that absorb energy
121 - Nature of Chemical Reactions Key Questions :When do chemical reactions take place?What is the role of energy in chemical reactions?
132 - Chemical Equations Key Questions : What is a chemical equation? What can a balanced chemical equation tell you?
14Describing Reactions Can write a word equation A chemical equation uses symbols to represent a chemical reaction and shows the relationship between the reactants and products
15Conservation of Mass An equation must be balanced CH4 + O2 CO2 + H2O ( NOT BALANCED )CH4 + 2O2 CO2 + 2H2O ( BALANCED )Balance by adding coefficients so that there are EQUAL NUMBERS OF EACH ELEMENT on both sides of the “Yield” sign
16Balanced Equations & Mole Ratios A balanced equation indicates the molar ratioThis is the proportion of reactants and productsOr relative amounts of a reactant to productCH4 + 2O2 CO2 + 2H2OMolar Ratio of methane to carbon dioxide?Molar ratio of methane to oxygen?
17Molar Ratios can be shown as MASS How do we do this?
182 - Chemical Equations Key Questions : What is a chemical equation? What can a balanced chemical equation tell you?
193 – Reaction Types Key Questions : How does learning about reaction types help in understanding chemical reactions?In which kinds of chemical reactions do the numbers of electrons in atoms change?
20Classifying Reactions Can use patterns to identify kinds of chemical reactions and to predict the products of the chemical reactionsFor example : small molecules join to form a larger one by a certain type of reaction
21Synthesis ReactionsSynthesis reactions occur when multiple substances combine to form a new compoundGeneral form : A + B ABSingle compound formedExample : plastic ( polymers – remember GOOP? )
22Decomposition Reactions Decomposition occurs when substances are broken apart ( Opposite of Synthesis )Cracking – large molecules of C and H (hydrocarbons) are broken apartDigestion – similar to crackingGeneral form : AB A + B
23Combustion Reactions CH4 + 2O2 CO2 + 2H2O ( methane combustion ) When oxygen reacts with a substance ( burning )Usually an organic materialHydrocarbonPlant matter ( wood ) or clothing ( cotton/polymeric )Not always though – ammonia ( NH3 )NH O2 NO H2O
24Displacement Reactions Single displacement rxn occurs when one atom appears to take the place of anotherGeneral form : AX + B BX + ADouble displacement rxn occurs when two compounds appear to exchange ionsGeneral form : AX + BY BX + AY
25Electrons & Chemical Reactions Free radical reactions and redox reactions can be understood as changes in the numbers of electrons that atoms haveFree radical is an atom or a group of atoms that has one unpaired electronRedox reactions ( oxidation-reduction ) occur when one substance loses electrons and another substance gains electrons
263 – Reaction Types Key Questions : How does learning about reaction types help in understanding chemical reactions?In which kinds of chemical reactions do the numbers of electrons in atoms change?
274 – Reaction Rates & Equilibrium Key Questions :What speeds up a reaction?What does a catalyst do?What happens when a reaction goes both directions
28What is Reaction Rate? How fast a reaction proceeds Can explain by finding the amount of products produced in a certain time interval
29What Speeds up Reactions? Higher temperaturesMore surface areaHigher reactant concentration( amount / vol )Pressure / Size of compound or molecule
30What is a catalyst?Speeds up or slows down a reaction but is not altered by the reactionIt does not participate as a reactant or a productIn your body – ENZYMES are catalysts
31Equilibrium Like balance when you are walking Balance between products and reactants when a reaction goes forward and backwards
324 – Reaction Rates & Equilibrium Key Questions :What speeds up a reaction?What does a catalyst do?What happens when a reaction goes both directions