2.2 Rates of Chemical Reactions
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2.2 Rates of Chemical Reactions

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2.2 Rates of Chemical Reactions 2.2 Rates of Chemical Reactions Presentation Transcript

  • Chapter 2Section 2 
  • Rates ofChemicalReaction s
  • How Fast?
  • Some reactions need some help to get started, others do not.
  • “What is thatextra help called?”
  • Activation Energy
  • The minimumamount of energy needed to start a reaction.
  • Let’s look at an example:2O2 + CH4 --> CO2 + 2H2O
  • Activation Energy 10
  • Activation Energy For a reaction to begin, the molecules must bump into each other or collide with enough force. 10
  • Activation Energy For a reaction to begin, the molecules must bump into each other or collide with enough force. The reactants must smash into each other with a certain amount of energy. If they do not, the reaction will not occur. 10
  • Activation Energy For a reaction to begin, the molecules must bump into each other or collide with enough force. The reactants must smash into each other with a certain amount of energy. If they do not, the reaction will not occur. This energy is called, activation energy. 10
  • Activation Energy For a reaction to begin, the molecules must bump into each other or collide with enough force. The reactants must smash into each other with a certain amount of energy. If they do not, the reaction will not occur. This energy is called, activation energy. This is also true for reactions that release energy when they react. An example is gasoline burning. 10
  • When gasoline is spilled it does not burst into flames.
  • A highly flammable material, which cannot be extinguishedby wind or rain needs to be lit in order to burn.
  • Rate of Reaction?
  • How fast a reaction occurs after it has started.
  • You can measure Reaction Rate by:- how quickly one of the reactants is consumed, or- how quickly one of the products is created
  • Rate of Reaction - Fast is Good
  • Rate of Reaction - Fast is Bad
  • What can we do to control reaction rate?
  • TemperatureChanges Rate
  • TemperatureChanges Rate
  • Temperature Changes Rate Slow the ripening of fruit by putting them in the refrigerator.
  • Temperature Changes Rate Slow the ripening of fruit by putting them in the refrigerator. Meat and fish decompose faster at higher temperatures, producing toxins that can make you sick. Keep them chilled helps slow the decomposition rate.
  • Temperature Changes Rate Slow the ripening of fruit by putting them in the refrigerator. Meat and fish decompose faster at higher temperatures, producing toxins that can make you sick. Keep them chilled helps slow the decomposition rate. Bacteria grow faster at higher temperature.
  • Temperature Affects Rate
  • Temperature Affects Rate
  • Temperature Affects Rate Most chemical reaction speed up when temperature increase.
  • Temperature Affects Rate Most chemical reaction speed up when temperature increase. The atoms and molecules are always moving, and they move faster at higher temperatures.
  • Temperature Affects Rate Most chemical reaction speed up when temperature increase. The atoms and molecules are always moving, and they move faster at higher temperatures. Faster molecules collide with each other more often and with greater force, which may be enough to break the old bond. This is activation energy.
  • Concentration Affects Rate
  • Concentration?
  • Amount of substancein a certain volume.
  • Surface Area Affects Rate 10 cm10 cm 10 cm
  • Surface Area Affects Rate Surface Area = 600 cm2 10 cm10 cm 10 cm
  • Surface Area Affects Rate Surface Area = 600 cm2 10 cm That is the amount of surface10 cm that would be 10 cm touching the other reactant.
  • Surface Area Affects RateWhat if we cut out little cubes? 1cm x 1cm 10 cm 10 cm 10 cm
  • Surface Area Affects RateWhat if we cut out little cubes? 1cm x 1cm 10 cm How many cubes 10 cm would we have? 10 cm
  • Surface Area Affects RateWhat if we cut out little cubes? 1cm x 1cm 10 cm How many cubes 10 cm would we have? 10 cm 1000 cubes
  • Surface Area Affects RateWhat if we cut out little cubes? 1cm x 1cm 10 cm How many cubes 10 cm would we have? 10 cm 1000 cubes What would be the SA of one of the cubes?
  • Surface Area Affects RateWhat if we cut out little cubes? 1cm x 1cm 10 cm How many cubes 10 cm would we have? 6cm 2 10 cm 1000 cubes What would be the SA of one of the cubes?
  • Surface Area Affects RateWhat is the total SA of all the cubes? 10 cm 10 cm 10 cm
  • Surface Area Affects RateWhat is the total SA of all the cubes? 10 cm 6cm 2 x 1000 = 10 cm 10 cm
  • Surface Area Affects RateWhat is the total SA of all the cubes? 10 cm 6cm 2 x 1000 = 10 cm 6000 cm2 10 cm
  • Surface Area Affects RateWhat is the total SA of all the cubes? 10 cm 6cm 2 x 1000 = 10 cm 6000 cm2 10 cm SA of Whole cube = 600 cm2 SA of cut up cube = 6000 cm2
  • Surface Area Affects Rate That’s a BIG difference! 10 cm10 cm 10 cm
  • Surface Area Affects Rate That’s a BIG difference! 10 cm10 cm 10 cm SA of Whole cube = 600 cm2 SA of cut up cube = 6000 cm2
  • Slowing DownReactions
  • Inhibitor?
  • A substance that slows down a chemical reaction. Aninhibitor makes the formation of a certain amount of product take longer.
  • InhibitorButylated hydroxytoluene (BHT)
  • Speed Up Reactions
  • Catalyst?
  • A substance that speeds up a chemical reaction. Catalyst’s do not appear in achemical equation because they are not changed permanently or used up.
  • Catalysts - provide a surface for the reaction to take place, or- reduce the activation energy needed to start the reaction
  • 38
  • Catalytic Converter
  • Catalytic Converter
  • Catalytic ConverterIn vehicles, the exhaust passes through thecatalyst.
  • Catalytic ConverterIn vehicles, the exhaust passes through thecatalyst.Catalysts will speed up the reactions thatchange incompletely burned substances thatare harmful, such as carbon monoxide, intoless harmful substances like CO2 and H2O.
  • Catalytic ConverterIn vehicles, the exhaust passes through thecatalyst.Catalysts will speed up the reactions thatchange incompletely burned substances thatare harmful, such as carbon monoxide, intoless harmful substances like CO2 and H2O.This results in cleaner air.
  • Catalytic Converter
  • Catalytic Converter
  • Enzymes are Specialists!
  • Enzyme?
  • Large protein molecules thatspeed up reactions needed for your cells to work properly. - convert food to fuel - build bone and muscle tissue - convert extra energy to fat - produce other enzymes
  • Other Uses of EnzymesOne example is Proteases - a class of enzymesthat work within cells to break down proteins.Meat tenderizer is one example of a protease. Contact lens cleaning solutions also containproteases that break down proteins formed byyour eyes that can collect on your lenses and cloud your view.
  • Finished the KNP! So, lets see acatalyst at work!