Chemistry Basics – Punjab TET (General Awareness & Current Affairs)
Purpose: Quick, clear, and exam‑friendly notes covering the fundamentals of chemistry that are frequently tested in the Punjab TET G.A & CA paper.
1. Simple Explanation
Chemistry is the science that studies matter, its properties, how it changes, and how it interacts with other matter.
In the TET syllabus, the focus is on the basic concepts that form the foundation for higher chemistry, such as:
- Atomic structure
- Periodic table & trends
- Chemical bonding (ionic, covalent, metallic)
- States of matter & phase changes
- Solutions & concentration
- Acids, bases, salts & pH
- Simple lab safety & common chemical reactions
2. Key Points
| Concept | What It Means | Why It Matters for TET |
|---|---|---|
| Atoms | Smallest unit of an element; made of protons, neutrons, electrons | Basis for all chemical formulas |
| Molecule | Two or more atoms bonded together | Explains compounds students encounter |
| Periodic Table | Organized by increasing atomic number and electron configuration | Helps recall element properties |
| Period Trends | Atomic radius ↑ left → right; Ionisation energy ↑ right → left | Predicts reactivity patterns |
| Chemical Bonds | Ionic (electron transfer), Covalent (electron sharing), Metallic (electron sea) | Explains physical properties (melting point, conductivity) |
| States of Matter | Solid, Liquid, Gas; phase changes (melting, boiling, sublimation) | Useful for everyday phenomena |
| Solutions | Homogeneous mixtures; solute + solvent | Basis for concentration calculations |
| Molarity | moles of solute per litre of solution | Common in lab procedures |
| Acid–Base Concept | Arrhenius (H⁺ / OH⁻), Brønsted–Lowry (proton donor/acceptor) | pH scale, neutralisation reactions |
| pH Scale | 0–14; <7 acidic, >7 basic, 7 neutral | Quick assessment of solutions |
| Lab Safety | PPE, handling chemicals, emergency procedures | Avoids accidents; mandatory for teachers |
| Common Reactions | Combustion, oxidation–reduction, precipitation | Illustrative of reaction types |
3. Worked Example
Problem
A 0.250 M solution of sodium chloride (NaCl) is prepared. How many grams of NaCl are required to make 200 mL of this solution?
Step‑by‑Step
| Step | Calculation | Result |
|---|---|---|
| 1. Find moles of NaCl needed | Molarity (M) = moles / litres → moles = M × litres | moles = 0.250 M × 0.200 L = 0.050 mol |
| 2. Calculate molar mass of NaCl | Na = 22.99 g mol⁻¹, Cl = 35.45 g mol⁻¹ → NaCl = 22.99 + 35.45 = 58.44 g mol⁻¹ | |
| 3. Convert moles to grams | grams = moles × molar mass | grams = 0.050 mol × 58.44 g mol⁻¹ = 2.92 g |
Answer: 2.92 g of NaCl must be dissolved in 200 mL of water to obtain a 0.250 M solution.
4. Quick Revision Summary
- Atoms → protons, neutrons, electrons.
- Molecules → bonded atoms.
- Periodic Table → order by atomic number; key trends: radius, ionisation energy.
- Chemical Bonds → ionic (charge), covalent (shared), metallic (delocalised).
- States & Phase Changes → solid → liquid → gas.
- Solutions → solute + solvent. Molarity = moles/ litre.
- Acids & Bases → Arrhenius, Brønsted–Lowry; pH scale.
- Lab Safety → PPE, label chemicals, know emergency steps.
- Common Reactions → combustion, reduction‑oxidation, precipitation.
Tip for TET: Focus on definitions, simple calculations, and quick recall of periodic trends. Use flashcards or mind‑maps for the periodic table.