CHEMICAL REACTION

• chemical reaction is a process that leads to a change in substances
• chemical reaction involves rearrangement of atoms or molecules into different structures
• in a chemical reaction, the change is caused by the breaking or forming of bonds between the outermost electrons of the atoms
• a chemical reaction can consume or release energy
• a chemical reaction is different from a physical change
• The symbolic representation of a chemical reaction is a CHEMICAL EQUATION
• Coefficients (whole numbers) are placed in front of substances to balance the equation and to indicate the number of units (atoms, molecules, moles, or ions) of each substance that are reacting.
• Chemical reactions always involve change.

  TRUE
• Atoms, molecules or ions rearrange to form different substances.
• The substances entering the reaction are called reactants.
• The substances formed in the reaction are called products.
• During reactions, chemical bonds are broken and new bonds are formed.
• A chemical equation is a shorthand expression for a chemical change or reaction.
• A chemical equation uses the chemical symbols and formulas of the reactants and products and other symbolic terms to represent a chemical reaction.
• Conditions required to carry out the reaction may be placed above or below the arrow.
• The physical state of a substance is indicated by symbols such as (l) for liquid.
• The law of conservation of mass states that in a chemical reaction mass is neither created nor destroyed.
• TYPES OF CHEMICAL REACTIONS

  • Combination
  • Decomposition
  • Single-Displacement
  • Double-Displacement
• meaning: plus

  location: placed between substances

  
• meaning: yields

  location: between reactants and products

  
• meaning: solid

  location: after formula

  
• meaning: liquid

  location: after formula

  
• meaning: gas

  location: after formula

  
• meaning: aqueous

  location: after formula

  
• meaning: heat

  location: written above or below yields

  
• meaning: light energy

  location: written above yields

  
• meaning: gas formation

  location: after formula

  
• COMBINATION - two reactants combine to form one product
• A + B → AB

  COMBINATION
• 2Ca(s) + O2(g) → 2CaO(s)

  COMBINATION
• N2(g) + O2(g) → 2NO(g)

  COMBINATION
• 2Al(s) + 3Cl2(g) → 2AlCl3(s)

  COMBINATION
• N2O5(g) + H2O(l) → 2HNO3(aq)

  COMBINATION
• Decomposition Reactions - a single substance breaks down togive two or more different substances.
• AB → A + B

  DECOMPOSITION
• 2Ag2O(s) → 4Ag(s) + O2(g)

  DECOMPOSITION
• 2NaHCO3(s) → Na2CO3(s) + H2O(g) + CO2(g)

  DECOMPOSITION
• 2H2O2(l) → 2H2O(l) + O2(g)

  DECOMPOSITION
• Single Displacement Reactions - one element reacts with a compound to replace one of the elements of that compound.
• A + BC → AC + B

  SINGLE DISPLACEMENT REACTION