SCI10 Q4 MOD3

Changes in Matter

  • Types of Changes

    • Matter undergoes two types of changes:

      1. Physical Change:

        • Involves changes in appearance without altering the composition.

        • Example: Ice melting, sugar dissolving in water.

      2. Chemical Change:

        • Alters both appearance and composition, forming new substances.

        • Example: Rusting of iron, baking a cake.

Activity 1: Classification of Changes

  • Examples Given:

    1. Healing of wounds – Chemical Change

    2. Rotting of banana – Chemical Change

    3. Opening a carbonated soft drink – Physical Change

    4. Dissolving sugar in water – Physical Change

    5. Painting a piece of wood – Physical Change

    6. Photosynthesis – Chemical Change

    7. Crushing chunks of ice – Physical Change

    8. Milk turning sour – Chemical Change

    9. Ice cream melts under the sun – Physical Change

    10. Cutting of stainless metal plate – Physical Change

Chemical Reactions

  • A chemical reaction is indicated by several signs:

    • Production of heat and light

    • Formation of a precipitate

    • Evolution of gas

    • Change in color

    • Change in temperature

  • Chemical Equation:

    • Symbolic representation of a chemical reaction.

    • Parts of a Chemical Equation:

      • Reactants: Substances present before the reaction (left side).

      • Products: Substances formed after the reaction (right side).

      • Arrow (→): Separates reactants from products and indicates a reaction has occurred.

Common Symbols in Chemical Equations

  • +: Substances are added or mixed.

  • →: Yields, makes, or produces.

  • ↓: Precipitate formed.

  • ↑: Indicates a gas has evolved.

  • (s): Solid form.

  • (l): Liquid form.

  • (g): Gas form.

  • (aq): Aqueous solution; substance is dissolved in water.

Types of Chemical Reactions

  1. Combination (Synthesis):

    • A + B → AB

    • Example: Sodium (Na) + Chlorine (Cl2) → Sodium Chloride (NaCl)

  2. Decomposition:

    • AB → A + B

    • Example: Sodium Chloride (NaCl) → Sodium (Na) + Chlorine (Cl2)

  3. Single Displacement (Replacement):

    • AB + C → AC + B

    • Example: Potassium bromide (KBr) + Chlorine (Cl2) → Potassium chloride (KCl) + Bromine (Br2)

  4. Double Displacement (Replacement):

    • AB + CD → AD + CB

    • Example: Silver nitrate (AgNO3) + Magnesium chloride (MgCl2) → Silver chloride (AgCl) + Magnesium nitrate (MgNO3)

  5. Combustion (Burning):

    • CnHn + O2 → CO2 + H2O

    • Example: Methane (CH4) + Oxygen (O2) → Carbon dioxide (CO2) + Water (H2O)

  6. Acid-Base (Neutralization):

    • Acid + Base → Salt + Water

    • Example: Hydrochloric acid (HCl) + Sodium hydroxide (NaOH) → Sodium chloride (NaCl) + Water (H2O)

Law of Conservation of Mass

  • Matter cannot be created nor destroyed, only transformed.

  • Total mass before and after a chemical reaction remains constant.

  • Activity: Analyze whether reactions conform to this principle by balancing chemical equations.

Steps to Balance a Chemical Equation

  1. Identify reactants and products.

  2. Count atoms of each element on both sides.

  3. Add coefficients to balance the number of atoms.

  4. Ensure the equation complies with the Law of Conservation of Mass.