experiment

  • Introduction

    • Reminder for next week’s experiments:
    • Bring printed worksheet.
    • Latecomers (10 mins) will not be allowed into the lab.
    • Importance of having your worksheet ready to avoid writing in notebooks last minute.

  • Lab Safety and Guidelines

    • Lab coat and safety glasses: Mandatory upon entry for safety.
    • Mobile phones: Must be off to avoid contamination.
    • PLAQ: Worth 1% of total score for each practical, and worksheet marks will clarify feedback with grades being adjusted to five instead of six.

  • Overview of Topics

    • Focus on chemical reactions in Topics 3 and 4.
    • Objective: Differentiate between chemical and physical changes, write chemical equations, and calculate quantities of products formed.

  • Chemical Reactions

    • Chemical vs. Physical Change:
    • Chemical Change: Involves breaking/forming bonds and results in new substances (e.g., iron rusting, digestion).
    • Physical Change: Change in state (solid to liquid) without altering the substance's chemical composition (e.g., melting ice).

  • Key Terminology

    • Reactant: Initial substances in a reaction.
    • Product: Substances formed after the reaction.

  • Writing Chemical Equations

    • Include states in equations:
    • (s): solid
    • (l): liquid
    • (g): gas
    • (aq): aqueous solution.
    • Example of combustion reaction:
    • Hydrocarbon + O2 → CO2 + H2O (water in gas form).
    • Stoichiometric coefficients: Whole numbers indicating the ratio of reactants and products.
    • Conservation of mass: Number of atoms in reactants equals number of atoms in products.

  • Balancing Chemical Equations

    • Steps to Balance:
    1. Identify and write unbalanced equation.
    2. Balance less occurring elements (typically avoid H and O until last).
    3. Adjust coefficients to achieve equal number of atoms for each element on both sides.
    • Example of balancing using Al and HCl:
    • Start with Al and HCl to generate AlCl3 and H2.
    • Count atoms per side and adjust coefficients respectively until sides equal.

  • ### Practical Considerations in Experiments

    • Practice balancing exercises repeatedly.
    • Use tools like flashcards or Menti for further practice and quizzes.

  • Final Notes:

    • Check understanding regularly and be proactive in asking questions.
    • Homework assigned: Practice different equations at home, balancing them for comprehension.
    • Importance of communicating issues (like screen sharing) promptly for better learning efficacy.