Chapter 6.2
description
Transcript of Chapter 6.2
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Chapter 6.2
Chemical Reaction
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Chemical Reactions
• Process by which atoms or groups of atoms in substances reorganize into different substances
• Chemical bonds are broken or formed
• For example – 4 Fe + 3 O2 2 Fe2O3
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Reactants and ProductsChemical Equation:
C6H12O6 + O2 CO2 + H20(Glucose and oxygen react to form carbon dioxide and water)
Reactants (starting substances):C6H12O6 + O2
Products (substances formed):CO2 + H20
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Balanced Equation• According to the principle of conservation of
mass, matter cannot be created or destroyed• The number of atoms of each element on the
reactant side must equal the number of atoms of the same element on the product side
For example:
2 H2O2 2 H20 + O2
C6H12O6 + 6 O2 6 CO2+ 6 H20
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Energy of Reactions
• Activation Energy – minimum amount of energy needed to start a chemical reaction; energy needed for reactants to form products
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Energy of ReactionsEnergy-Absorbing Reaction Energy-Releasing Reaction
Products
Products
Activation energy
Activation energy
Reactants
Reactants
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Enzymes
• Most chemical reactions proceed slowly since the activation energy is high
• A catalyst is a substance that lowers the activation energy needed to start a chemical reaction
• Enzymes are biological catalysts; enzymes are proteins
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Enzymes
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How Enzymes Work
1. Reactants, called substrates, bind to specific enzymes; the site where enzymes bind is called the active site
2. Once the substrate binds to the active site, it changes shape and forms the enzyme-substrate complex
3. The substrates react to form new products; the enzyme-substrate complex helps to break and form bonds
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Example of Enzyme Reaction
http://blog.poolcenter.com/print.asp?articleid=6072
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Another View of Enzymes
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EnzymesMany factors can affect enzyme activity such as:
– pH– Temperature– Concentration of substrates
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Chapter 6.3
Water and Solution
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Water’s Polarity• Water molecules are formed by
covalent bonds between 2 hydrogens and 1 oxygen atom
• Since the electrons are more strongly attracted to the oxygen, the electrons spend more time near the oxygen nucleus
• The unequal distribution of electrons gives oxygen a slight negative charge
• Molecules with an unequal distribution of charges are polar molecules – they have oppositely charged regions
Slight Negative Charge
Slight Positive Charge
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Water’s Polarity and Hydrogen Bonds• The two water molecules are
brought together, their polar ends attract each other
• This attraction between water molecules is called hydrogen bonding
• It is a weak bond between the hydrogen of one atom and the oxygen of another
• A water molecule can hydrogen bond with three other water molecules
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Hydrogen Bonding in Water
http://commons.wikimedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.jpg
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Properties of WaterWater is the UNIVERSAL SOLVENT
• Because water is polar, it can dissolve many substances
• For example, NaCl
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Properties of WaterWater Expands When It Freezes
• Because of hydrogen bonding, water molecules separate when freezing and water becomes less dense
• Extremely important for marine organisms
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http://expertvoices.nsdl.org/polar/2009/02/03/teaching-about-snowflakes-a-flurry-of-ideas-for-science-and-math-integration/http://cc.oulu.fi/~nmrwww/comp_res4.html
Liquid WaterSolid Water (Ice)
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Properties of WaterWater is COHESIVE and ADHESIVE
Because of hydrogen bonding, – Water is attracted to other water molecules – this
is called COHESION– Water is attracted to other surfaces – this is called
ADHESION
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Cohesion
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Cohesion Causes Surface Tension
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Adhesion
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Adhesion (Capillary Action)
http://discovermagazine.com/2003/mar/featscienceofhttp://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_p033.shtml
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Mixtures
• two or more substances which are combined so that each substance keeps its own chemical identity.– Water combines to form many types of mixtures
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Mixtures• Mixtures can be classified as
– Homogeneous – a combination of substances that is uniform throughout
or – Heterogeneous – a combination of substances that are
physically distinct from one another
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Homogenous Mixtures
• Same uniform appearance
• Same composition throughout
• Examples– Sugar water– Salt water– Water and vinegar– Air in the atmosphere
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Homogeneous Mixture• Solutions are a
homogeneous mixture• There are two components
of solution:– Solvent – a substance in
which another substance is dissolved
– Solute – the substance that is dissolved
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Heterogeneous Mixture
• Visibly different substances
• Components remain distinct
• Examples – – Vinegar and oil– Salad (lettuce,
vegetables, croutons, etc.)
– Sand and water
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Acids and Bases
WATERH2O
ACIDS BASES
Substances that release H+ ions when dissolved
in water
Substances that release OH- ions when dissolved
in water
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pH ScaleH2O H+ + OH-
•pH scale – measurement system used to indicate the concentration of H+ ions in a solution•pH scale ranges from 0-14
• pH 7 is neutral and the concentration of H+ ions and OH- ions is equal• Acids – any compound that forms H+ ions in solution; contain pH values less
than 7 (the lower the pH values, the higher the acidity)• Bases – a compound that produces hydroxide ions (OH-) in solution; contain
lower concentrations of H+ ions than water and have pH value greater than 7
•Buffers • weak acids or bases that can react with strong acid or bases to prevent sudden
changes in pH• For example, to buffer a strong acid, you would add a weak base
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Chapter 6.4
The Building Blocks of Life
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Organic Chemistry
• Organic compounds are those containing CARBON
• Life forms are carbon-based and therefore considered organic
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Macromolecules
• Macromolecules – large molecules that form from joining smaller molecules together– The smaller molecules are called monomer– The larger molecules are called polymers
• Four biologically important macromolecules:– Carbohydrates– Lipids– Proteins– Nucleic acids
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Macromolecules
Monomer – smaller molecule
Polymer – larger molecule formed by joining together smaller molecules
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Biological MacromoleculesGroup Function
Carbohydrates - Store Energy
Lipids - Store energy- Provide cellular barriers
Proteins - Transport substances- Speed up reactions-Provide structural support-Make hormones
Nucleic Acids Store and communicate genetic information
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CarbohydratesChemical Composition•Made of Carbon, Hydrogen , and Oxygen
•Ratio of 1:2:1 (# of C atoms: # of H atoms: # of O atoms)Or (CH2O)2
Functions in Living Things
•ENERGY!• Structural support (cellulose in plant cell walls or chitin in animal shells)
Structure• Monomers may be small carbohydrates like glucose or sucrose. These monomers are called monosaccharide
• The monomers join to form large polymer called polysaccharides
Examples
Sucrose – table sugar
Cellulose – support of plant cell walls
Chitin – rigid support for animal shells (ex. lobster)
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LipidsChemical Composition
• Made of Carbon, Hydrogen, and Oxygen
• Higher ratio of Hydrogen to Carbon
Functions in Living Things
ENERGY storage
Provide barriers for cell (cell membranes)
Protective layersStructure
Composed of several fatty acids attached to glycerol
Examples
Fats
Waxes – protective coating on leaves
Oils
Biological steriods
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ProteinsChemical Composition
Composed of Carbon, Hydrogen, Oxygen, Nitrogen, and sometimes Sulfur
Functions in Living Things
Transport substances
Speed up chemical reactions
Hormones
Structural supportStructure
•Monomers of proteins are amino acids
• The monomers, amino acids, join to form long chains of proteins
Examples
Enzymes – speed up chemical reactions
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Nucleic AcidsChemical Composition
Composed of Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus
Functions in Living Things
Store genetic information
Structure
• Smaller monomers, called nucleotides, join together to form long polymers, DNA and RNA
Examples
DNA – stores genetic information
RNA – copies and transmit genetic information; help to make proteins