Chemistry — SSC GD Study Notes

Overview

Chemistry questions in SSC GD exams test basic understanding of matter, the periodic table, and everyday chemical phenomena. You will encounter 3–5 questions covering elements, compounds, acids, bases, salts, and simple chemical reactions. The focus is on fundamental concepts rather than complex calculations—knowing definitions, properties, common examples, and practical applications is more important than numerical problem-solving.

This topic overlaps significantly with your daily life. Understanding acids and bases helps you grasp why lemon juice tastes sour, why soap feels slippery, or why antacids relieve acidity. Chemical reactions explain rusting, cooking, and combustion. The periodic table organizes all elements by their properties, making it easier to remember trends rather than isolated facts.

Master the classification of matter, memorize 25–30 key elements with their symbols and uses, understand the pH scale, and know 10–12 common acids, bases, and salts with their formulas and applications. Questions are typically direct—asking for chemical names, formulas, properties, or real-world uses.

Key Concepts

• **Matter exists in three states**: solid (fixed shape and volume), liquid (fixed volume, variable shape), and gas (variable shape and volume). Changes between states—melting, boiling, condensation, sublimation—are physical changes, not chemical.

• **Elements are pure substances** made of one type of atom, like oxygen (O), gold (Au), or carbon (C). Compounds are substances formed by chemical combination of two or more elements in fixed ratios, like water (H₂O) or salt (NaCl).

• **The periodic table arranges elements** by increasing atomic number. Elements in the same vertical group share similar properties. For example, Group 1 contains alkali metals (sodium, potassium) that are highly reactive, and Group 18 contains noble gases (helium, neon) that are inert.

• **Acids are substances that release hydrogen ions (H⁺)** in water, taste sour, turn blue litmus red, and react with metals to produce hydrogen gas. Common acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and acetic acid (CH₃COOH).

• **Bases are substances that release hydroxide ions (OH⁻)** in water, taste bitter, feel slippery, turn red litmus blue, and neutralize acids. Common bases include sodium hydroxide (NaOH), calcium hydroxide [Ca(OH)₂], and ammonium hydroxide (NH₄OH).

• **pH scale measures acidity or alkalinity** from 0 to 14. pH < 7 is acidic, pH = 7 is neutral (pure water), and pH > 7 is basic/alkaline. Strong acids have pH 1–2, strong bases have pH 13–14.