Chemical Reactions

Chemical Reactions

  1. Definition:

    • A chemical reaction is a process in which substances interact to form different substances by breaking, forming, or rearranging chemical bonds.

    • Substances involved can be ionic or covalent compounds, or the atoms, ions, or molecules of elements.

  2. Example: Photosynthesis

    • Photosynthesis is a chemical reaction in which plants make food using the sun's energy.

    • Reactants: Carbon dioxide (CO₂) and water (H₂O).

    • Products: Glucose (C₆H₁₂O₆) and oxygen (O₂).

  3. Reactants and Products:

    • Reactants: The substances that undergo change (e.g., carbon dioxide and water in photosynthesis).

    • Products: The new substances formed (e.g., glucose and oxygen).

    • Reactants and products are made up of the same elements, but their arrangement changes.

  4. Chemical Equation:

    • A chemical equation represents a chemical reaction.

      • Reactants' formulas are written on the left, and products' formulas are written on the right.

    • Example:

      • CO₂ + H₂O → C₆H₁₂O₆ + O₂

    • The equation must show the same elements in both reactants and products.

    • Balanced Equation: The number of atoms for each element on the left side must equal the number on the right, according to the law of conservation of matter (matter cannot be created or destroyed, only rearranged).

  5. Balancing a Chemical Equation:

    • The equation must be balanced to comply with the law of conservation of matter.

      • In photosynthesis, six molecules of carbon dioxide react with six molecules of water to produce one molecule of glucose and six molecules of oxygen:

      • Balanced Equation:

        • 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

    • Coefficients: Numbers in front of chemical formulas that indicate the number of molecules (e.g., 6 for carbon dioxide and water).

  6. Key Concepts:

    • Chemical Bonds: In a chemical reaction, bonds in the reactants are broken, and new bonds are formed to create the products.

    • Reactants: The substances that undergo change in a chemical reaction.

    • Products: The new substances produced by the reaction.

    • Chemical Equation: A written expression showing the reactants and products with their chemical formulas.

    • Balanced Equation: Ensures that the number of atoms of each element is the same on both sides of the equation.