Chemical Reactions

Why Do We Need To Study Chemical Reactions?

• Happens in everyday life

Chemical Reactions

• Process where substances (reactants) change into new substances (products) with different properties

• Due to breaking and forming of chemical bonds

  • Leads to new molecular arrangements

• Types of Chemical Reactions

  • Physical

    • No new substance is formed

    • Only the appearance changes

  • Chemical

    • A new substance with new properties is created

    • Irreversible usually

• Signs of Chemical Reactions

  • Color changes

  • Production of gas

  • Change in temperature

  • Formation of precipitate

    • Insoluble solid that occurs when 2 substances combine

  • Odor change

  • Light emission

Parts of a Chemical Equations

2A_(s) + B_(I) -> 2AB_(g)

• Left side = reactants

• Right side = product

• + = reacts with

• -> = yields of produces

• Number = coefficient

  • Tells you the number of molecules

• Subscript = phase of the chemical substance

  • S = solid

  • L = liquid

  • G = gas

  • Aq = aqueous solution

  • Number = number of atoms

Major Types of Chemical Reactions

• Combination Reaction (Synthesis)

  • 2 or more reactance combine to form one product

  • A + B -> AB

  • Gets together

• Decomposition Reactions

  • Single reactant breaks apart into 2 or more products

  • AB -> A + B

  • Breaks up

• Single replacement reactions

  • 1 element replaces another in a compound

  • A + BC -> AC + B

  • Couple + 3rd party

  • More reactive molecules will attract the other electron

• Double replacement reaction

  • 2 compounds swap to form 2 new compound

  • AB + CD -> AD + CB

  • Couple swap

  • Always follows opposites attract

• Combustion Reaction

  • A fuel (hydrocarbon) reacts with oxygen to produce carbon dioxide, water, and energy

  • CxHy reacting with O₂

  • Products will be heat & light + water + CO₂ or water + CO₂ + carbon

  • Blue flame = complete combustion

    • Enough oxygen interacting with hydrocarbon

  • Yellow flame = incomplete combustion

    • Not enough oxygen to react with hydrocarbon

Balancing Chemical Reactions

• Based on Law of Conservation of Mass

  • Matter cannot be created nor destroyed, only arranged

  • Mass of reactant = mass of the product

  • Atoms are just rearranged, not lost or gained

• Steps

  • List down the elements on both sides of the equation

  • Count the atoms of each element on both sides

  • Adjust the coefficients to balance

• Key Reminders

  • Only change the coefficient

  • Never change subscript