Science balancing chemical

• The learners demonstrate the chemical reactions associated with biological and industrial processes affecting life and the environment
• Chemical reactions are happening all the time around us and we just do not realize it
• Chemical reactions happen when molecules from one substance break apart and combine, to some degree, with another to form a new substance
• Some reactions give off heat, some take in heat, some give off brilliant colors, some give off light, and some show a change in color and odor
• Many chemical reactions can be classified as one of six basic types: combination, decomposition, single replacement, double displacement, combustion, and acid-base reaction
• Combination reactions involve 2 or more substances combining to form a single new substance
• Decomposition reactions involve a compound breaking down into two or more simpler substances
• Single replacement reactions involve one element replacing another element in a compound
• Double displacement (metathesis) reactions involve the positive and negative ions of two compounds exchanging places to form two new compounds
• Combustion reactions involve a hydrocarbon reacting with oxygen to form water and carbon dioxide
• Acid-base reactions are a type of double displacement reaction where an acid and base react to form a salt and water
• The Law of Conservation of Mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations, it is merely rearranged
• According to the Law of Conservation of Mass, there must be the same number and kind of atoms after a chemical reaction as were present before the reaction
• Both the initial and final substances in a chemical reaction are composed of atoms because all matter is composed of atoms
• According to the Law of Conservation of Mass, there must be the same number and kind of atoms after the chemical reaction as were present before the chemical reaction
• The Law of Conservation of Mass is the guiding principle behind balancing chemical equations
• Activity to investigate how the number of atoms in each element is conserved in a chemical reaction

  1. Sort paper clips by color to represent elements

  2. Make model representations of molecules O2, H2, H2O

  3. Balance the chemical equation H2 + O2 → H2O
• Coefficients

  Indicate the number of each substance involved in the reaction, may be changed to balance the equation
• Subscripts


  Part of the formula, cannot be changed as it would change the chemical identity of the species
• Steps in balancing equations through inspection

  1. Identify reactants and products

  2. Take note of elements present

  3. Count number of atoms of each element

  4. Change coefficients until atoms are balanced

  5. Check that atoms are balanced
• Chemical equations to balance

  • SeCl6 + O2 → SeO2 + Cl2
  • AgNO3 + Cu → Cu(NO3)2 + Ag
  • etc.
• The Law of Conservation of Mass states that mass is conserved in a chemical reaction. The total mass of the reactants is equal to the total mass of the products
• For a chemical equation to conform to the Law of Conservation of Mass, it has to be balanced
• Chemical equations are balanced by placing the appropriate coefficients before the symbols or formulas of reactants and products