Chemistry
About 7 min · Mathematics and Science (Paper II) · English
Time worked out from the lesson's 485 words at 150 words a minute, plus a minute for each question.
Chemistry is part of the Science section in AP TET Paper II, covering fundamental concepts taught in classes 6-8. This topic tests your understanding of matter, its composition, properties, and the changes it undergoes. Questions can assess both conceptual clarity and the ability to explain everyday chemical phenomena to upper primary students.
Key ideas
- Matter is made of tiny particles — All substances consist of atoms and molecules in constant motion, with spaces between them. This explains diffusion, dissolution, and state changes.
- Three states of matter have distinct properties — Solids have fixed shape and volume (particles tightly packed), liquids have fixed volume but take container's shape (particles less tightly packed), gases have neither fixed shape nor volume (particles far apart and move freely).
- Physical vs chemical change — Physical changes are reversible and don't form new substances (ice melting). Chemical changes form new substances with different properties (burning paper).
- Elements are purest forms — Elements cannot be broken into simpler substances by chemical means. 118 elements exist, organised in the Periodic Table by atomic number.
- Compounds vs mixtures — Compounds have fixed composition and chemical bonding (water H₂O). Mixtures have variable composition with no chemical bonding (salt water).
Watch out for
- Confusing dissolution with melting → Dissolution involves solute dispersing in solvent (sugar in water); melting involves solid changing to liquid state due to heat (ice to water). Both look like "disappearing" but mechanisms differ completely.
- Thinking all chemical changes are irreversible → While most are irreversible (burning), some chemical changes can be reversed under special conditions. The defining feature is formation of new substances, not irreversibility alone.
- Assuming strong smell indicates acid → Ammonia has a strong smell but is a base. Vinegar (acid) also smells. Use indicators, not smell, to identify acids and bases.
Quick reference
- Matter particle arrangement: Solid (tightly packed) → Liquid (loosely packed) → Gas (far apart)
- Three separation methods: Filtration for insoluble solids, evaporation for dissolved solids, distillation for liquid mixtures
- Acid-base indicators: Litmus (red/blue), turmeric (yellow→red in base), phenolphthalein (colourless→pink in base)
- Chemical change signs: Colour change, gas evolution, precipitate formation, temperature change, irreversibility
- Rusting prevention: Painting, oiling, galvanising (zinc coating), alloying (stainless steel)
Check yourself: 3 questions
1. A student dissolves 20 grams of common salt in 100 grams of water to make a salt solution. What is the mass of the solution formed?
2. Which of the following methods would be most suitable to separate a mixture of sugar and water?
3. When blue litmus paper is dipped in lemon juice, it turns red. When red litmus paper is dipped in baking soda solution, it turns blue. What can we conclude about the nature of these substances?
This lesson is cut from the topic's note, not rewritten. Fact-checked on 18 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.
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