Chemistry in Action

Key Terms  Synthesis  Decomposition  Polymerisation  Collision Theory  Kinetic Energy  Catalyst  Enzyme  Substrate  Active Site  Surface Area

Types of Chemical Reaction

 Synthesis  Using two products to create something new.  For example:  2H 2 + O 2  2H 2 O

Types of Chemical Reaction

 Decomposition  A substance is broken down to simpler products.  For example: CaCO 3  CaO + CO 2 OR 2H 2 O  2H 2 + O 2

Types of Chemical Reaction

Polymerisation  A large number of monomers (single parts) are joined together to form a long chain called a polymer (many parts).  High density polymers have little branching.  Low density polymers have a lot of branching.

Reaction Rates

Controlling Reaction Rates  There are a number of things we can do to control the rate of a reaction.  When designing a process chemists need to consider:  Should the reaction go quickly or slowly?  What would be the costs involved in controlling the reaction rate?  Are there any safety or environmental concerns?

 More particles colliding leads to more reactions. Collision Theory

 The particles must have the correct orientation. Collision Theory

 The particles must have enough energy to bring about a reaction. Collision Theory

Increasing Reaction Rate

 Increased temperature  Leads to increased frequency of collisions  Particles have greater kinetic energy Increasing Reaction Rates

 Increasing concentration of reactants.  Leads to increased frequency of collisions  NOTE: Increasing the pressure of a gas is equivalent to increasing concentration of reactants. Increasing Reaction Rates

 Use of catalysts.  Lowers the activation energy.  NOTE: Catalysts do not change during the reaction. They only facilitate it. Increasing Reaction Rates Haaaaave you met Ted?

Increasing Reaction Rates

Increasing Reaction Rate  Enzymes  A special category of biological catalysts.  They are proteins so they only work in certain pH and temperature ranges.  Enzymes are very specific and only work on a small range of substances.

Increasing Reaction Rates

 The lock and key model.  Substrate attaches to the active site on the enzyme.  Enzyme causes a reaction to occur.

Increasing Reaction Rates

 Increasing surface area  Allows for more collisions between particles.  Stirring is a way of increasing the surface area. Increasing Reaction Rates

Image Credits  ‘States of Matter’ by Wendy Adams et al available at courtesy of PhET Interactive Simulations at the University of Colorado.  ‘Induced Fit Diagram’ By Created by TimVickers, vectorized by Fvasconcellos (Provided by TimVickers) available at _fit_diagram.svg, via Wikimedia Commons _fit_diagram.svg