(SCI) Chemical Reactions

• S (symbol): the reactant or product is in the solid phase
• l (symbol): the reactant or product is in the liquid phase
• g (symbol): the reactant or product is in the gaseous phase
• aq (symbol): the reactant or product is in an aqueous solution (dissolved in water)
• right arrow (symbol): "yields"; indicates the results of the reaction
• left and right arrow (symbol): reversible
• down arrow (symbol): alternative to solid(s) but used only to indicate a precipitate
• ADDITION-COMBINATION-SYNTHESIS Reaction: A + B -> AB
• DECOMPOSITION: AB -> A + B
• SINGLE REPLACEMENT: A + BC -> AC + B
• DOUBLE REPLACEMENT REACTION: AB + CD -> AD + CB
• COMBUSTION: Chemical reaction in which a fuel undergoes oxidation by reacting with an oxidizing agent, resulting in the release of energy (usually in the form of heat).

  i.e. METHANOL (2CH3OH)
• ACIDS: starts with H

  BASES: ends with OH
• NEUTRALIZATION: An acid and base quantitatively react together to form a salt and water as products
• RATE OF REACTION: speed of reaction
• Reactions take place when particles COLLIDE with a certain amount of energy.
• ACTIVATION ENERGY - The minimum amount of energy needed for the particles to react.
• COLLISION THEORY - not all collisions between molecules result in a formation of products
• EFFECTIVE COLLISIONS OCCUR WHEN...

  • Colliding molecules possess a MINIMUM KE to start a chemical reaction
  • The reactant molecules should be in correct ORIENTATION when they collide
• (FACTORS): TEMPERATURE

  • The higher the temperature = faster rate of reaction
• (FACTORS): SURFACE AREA

  • Smaller the pieces = Larger surface area
  • Large surface area = More collisions = more chance of reactions
• (FACTORS): CONCENTRATION

  • Higher concentration = More particles
  • More particles = More likely to collide = More likely to react
• (FACTORS): Presence of a CATALYST

  • Substances that change the rate of a reaction without being used up in the reaction
  • Produces the SAME amount more quickly
  • (NEVER MORE)
• Presence of a CATALYST:

  i.e. NICKEL

  • Production of margarine (hydrogenation of vegetable oil)
  • Vegetable oils -> Fully saturated fats (solid fats) at room temp.
• IMPORTANCE OF CATALYSTS:

  • Products can be made more easily
  • Reduces the need for higher temperatures
• (EXAMPLES) - SURFACE AREA

  • Raw potatoes are sliced into thin slices for cooking
• (EXAMPLES) - CATALYST

  • Protein is broken down in the stomach by enzymes
• (EXAMPLES) - TEMPERATURE

  • Placing raw meat in the freezer to prevent from spoiling
• (EXAMPLES) - SURFACE AREA

  • Powdered sugar dissolves faster than the sugar cubes
• (EXAMPLES) - TEMPERATURE

  • A person fans the coal when grilling barbecue to sustain the heat
• (EXAMPLES) - CONCENTRATION

  • More bubbles seem to appear when a concentrated acid is added to a magnesium strip than when a diluted solution of the same acid is added
• INCREASING the concentration of reactants would be considered one way to make the product form FASTER.
• Increasing the temperature of the reactants INCREASES the rate of of chemical reactions, because it provides MORE ENERGY for the particles to move FASTER.
• (EXAMPLE) - How changing the concentration can change the rate of a chemical reaction

  The dough rises quickly in a warm place.

  (Increasing concentration of yeast = Increased rate of fermentation = Quicker rising time)
• (EXAMPLE) A beneficial way of slowing down a chemical reaction

  • Using batteries to provide energy
  • Burning of fuels in car engines
• A chemical reaction is a process in which

  • all reactants change state
  • the law of conservation of mass applies
• A chemical equation is balanced by ADDING coefficients.
• Zn + CuSO4 ----> ZnSO4 + Cu

  What are the products in the equation?

  ZnSO4 and Cu
• Quicklime (CaO) is used as a drying agent. When water is added to this, slaked lime CA(OH)2 is formed. What type of reaction is this?

  Combination
• Reactions eventually stop, because generally one or more of the reactants has been used up.