Secondary School Lesson Note for Chemistry

Chemistry is a fundamental subject for secondary school students in Nigeria, especially for those preparing for the WAEC exams. Understanding essential chemistry equations and reactions is crucial for passing your exams with flying colors. In this detailed overview, we'll cover some of the fundamental concepts and equations that every WAEC exam candidate needs to master.

Atomic Structure and Chemical Reactions

One of the first topics you'll come across in your lesson notes is atomic structure. Understanding atomic number, mass number, and isotopes is essential. The atomic number (Z) is the number of protons in an atom's nucleus, while the mass number (A) is the total number of protons and neutrons.

Basic chemical reactions involve the rearrangement of electrons to form new substances. Some common reaction types include:

• Combination Reactions: A + B → AB
• Decomposition Reactions: AB → A + B
• Single Displacement Reactions: A + BC → AC + B
• Double Displacement Reactions: AB + CD → AD + CB

Moles and Stoichiometry

The mole is a fundamental unit in chemistry. It's used to express the amount of a substance. One mole of any substance contains Avogadro's number of particles (6.02 × 10²³).

Stoichiometry involves the calculation of reactants and products in chemical reactions. Key equations to remember include:

• Molar Mass: The mass of one mole of a substance, usually expressed in grams per mole (g/mol).
• Calculating Moles: Moles = Mass (g) / Molar Mass (g/mol)
• Balancing Chemical Equations: Ensure the number of atoms of each element is the same on both sides of the equation.

Acids, Bases, and Salts

Understanding acids, bases, and salts is another critical aspect of secondary school chemistry. Acids are proton donors, while bases are proton acceptors. The pH scale measures the acidity or basicity of a solution:

• pH Scale: Ranges from 0 (very acidic) to 14 (very basic), with 7 being neutral.
• Neutralization Reactions: Acid + Base → Salt + Water

Common examples include the reaction of hydrochloric acid (HCl) with sodium hydroxide (NaOH) to produce sodium chloride (NaCl) and water (H₂O).

Organic Chemistry

Organic chemistry focuses on compounds primarily made of carbon and hydrogen. Key classes of organic compounds include:

• Alkanes: Saturated hydrocarbons with single bonds (e.g., methane CH₄, ethane C₂H₆).
• Alkenes: Unsaturated hydrocarbons with one or more double bonds (e.g., ethene C₂H₄).
• Alkynes: Unsaturated hydrocarbons with one or more triple bonds (e.g., ethyne C₂H₂).

Don't forget to refer to your class notes and engage with interactive resources like Green Bridge CBT learning resources to strengthen your understanding.