SCI REV P2

• Chemical Reaction


  A rearrangement of atoms in which some of the original bonds are broken and new bonds are formed to give different chemical structure
• Reactants


  One set of a new substance that is converted to a new set of substance called product
• Chemical Reaction


  • Atoms in the reactant are rearranged to form one or more different substances
  • The total number of atoms remains the same after the reaction
  • The original substances lose their identities and can no longer be recognized
  • The total mass of the reactants is equal to the total mass of the products
• Signs of Chemical Reactions


  • Change in color
  • Change in odor
  • Production of a new gases or vapor
  • Input or release of energy
  • Difficult to reverse
• Effective Collision


  Happens when chemical reaction occurs and forms a new product
• Ineffective Collision


  Does not cause any reaction and does not lead to the formation of products
• Activation Energy


  The minimum amount of energy that is required to activate atoms or molecules
• Reaction Mechanism


  1. Elementary Steps - series of simpler reactions that combine to form the overall reaction

  2. Intermediate - a substance produced in one elementary step if combined in another

  3. Catalyst - increases the rate but not consumed by reaction
• Unimolecular Reaction


  Only one reactant particle
• Bimolecular Reaction


  Involves two reactant particles
• Trimolecular Reaction


  Involves three reactant particles
• Exothermic Process


  A reaction that gives off energy, releases heat, and causes the temperature of the immediate surroundings to rise
• Endothermic Process


  A process that absorbs heat and cools the surroundings
• Spontaneous Reaction


  A chemical reaction that occurs naturally and continuously once it starts
• Non-Spontaneous Reaction


  Reactions that need continuous supply of energy for them to proceed
• Reaction Rate


  How quickly or slowly a reaction takes place
• Factors Affecting Rates of Chemical Reaction

  • Temperature
  • Concentration
  • Surface Area
  • Presence of a Catalyst
  • Nature of the Reactants
• Temperature


  The measure of the kinetic energy, or energy of motion, in the particles of a substance. As temperature increases, the particles move faster and come in contact more often.
• Surface Area


  For a reaction to occur, substances must come in contact with each other. Contact can only take place at the surfaces of the substances involved in the reaction. As the surface area increases, the rate of a reaction increases because more particles can come together.
• Concentration


  Tells us how much solute there is in a solution. As the concentration of the chemical increases, the chance of contact among particles also increases, causing an increase in the rate of reaction.
• Catalyst


  A substance that changes the rate of a chemical reaction by providing an alternate pathway, lowering the activation energy. Most of them speed up reaction but they are not changed or used up in a reaction.
• Application of Factors Affecting Rate of Reaction

  • Food and Pharmaceutical Products Preservation
  • Preservation or Decomposition of Specimens
  • Medication or Poison Affecting the Body
  • Dating, Restoration, Preservation of Artifacts
• Law of Conservation of Mass

  Also known as the Lomonosov-Lavoisier Law. States that the quality of mass of substance remains constant regardless of any change that takes place. The mass of the reactants must always be equal to the mass of the product.
• Law of Definite Composition


  Elements combined to form compounds always contain exactly the same proportion.
• Law of Multiple Proportion


  If two elements form more than one compound, the ratios of the masses of the second element combining with a fixed mass of the first elements will be in ratio of small whole numbers.

  
• Chemical Equation


  Used to illustrate a chemical reaction using symbols, formulas, and signs.
• Writing Chemical Equation


  1. Chemical formulas of element symbols are used instead of names

  2. Reactants are written on the left side and products on the right side

  3. In between the two reactants, the sign + is used as the word "and"

  4. To separate the products, add an arrow in the place between them

  5. There should be the same atoms on the reactant and the product side of the equation
• Combination or Synthesis Reaction

  Two or more substances react to form one product
• Analysis or Decomposition Reaction


  A reaction in which a single compound is broken down into two or more smaller compounds or elements
• Single Replacement (Substitution) Reaction

  An uncombined element displaces an element that is part of a compound

  
• Double Replacement (Metathesis) Reactions


  Atoms or ions from two different compounds replace each other