--- title: "Explosives: classification and requirements" subject: "Engineering Chemistry" chapter: 7 key: "semester_2/engineering_chemistry:explosive-classification" source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/explosive-classification site: BCT Engineering --- # Explosives: classification and requirements Engineering Chemistry · Chapter 7: Explosives - Asked in: 2071 Bhadra, 1+2+2 marks - Video: [Lec-39_Classification of explosives|Chemistry I|First Year Engineering](https://www.youtube.com/watch?v=kZRvxm_8c-c) — FIRST YEAR ENGINEERING_LJIET - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/explosive-classification - Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-7 ## Question What is an explosive? Classify explosives with examples. What is the requirement of good explosives? ## Short answer An explosive is a substance that undergoes rapid exothermic decomposition releasing hot gases, causing pressure rise. Explosives are classified as low (black powder, smokeless powder) that deflagrate, and high (primary: lead azide; secondary: TNT, RDX) that detonate; plastic explosives (C-4) are mouldable high explosives. Good explosives are stable, safe, easily initiated, have high brisance, produce large gas volume, and are cheap. ## Answer #### Explosive An **explosive** is a substance (or mixture) that, on heating, shock or friction, undergoes a very fast, highly exothermic decomposition that releases a large volume of hot gases, causing a sudden rise in pressure with heat, light and sound. #### Classification ```text Explosives ├── Low explosives (deflagrate) black powder, smokeless powder ├── High explosives (detonate) │ ├── Primary lead azide, mercury fulminate │ └── Secondary TNT, RDX, PETN, picric acid, dynamite └── Plastic explosives C-4, Semtex ``` - **Low explosives:** burn quickly, produce propelling effect; used as propellants. - **High explosives:** detonate with shattering effect; primary ones are initiators, secondary ones are the main charge. - **Plastic explosives:** moulded high explosives. #### Requirements of a good explosive 1. Stable during storage, without decomposing over time. 2. Safe to handle: not too sensitive to shock, friction or heat. 3. Easily exploded by a detonator or proper initiation. 4. High velocity of detonation and brisance (shattering power). 5. Large volume of gas released per unit mass, with high heat of explosion. 6. Gives little smoke and no poisonous fumes (for use in mines). 7. Cheap, easy to make from available raw materials, and non-hygroscopic. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is an explosive? A. A substance that undergoes very fast, highly exothermic decomposition releasing large volume of hot gas B. A substance that burns slowly C. A substance that absorbs heat D. An inert solid Answer: A. Sudden gas release and heat cause pressure rise, light and sound. (Key point: Definition) 2. Which grouping classifies explosives? A. Solid, liquid and gas only B. Acidic and basic C. Natural and artificial only D. Low, high (primary and secondary) and plastic Answer: D. Low (deflagrate), high (detonate; primary/secondary) and plastic explosives. (Key point: Classification) 3. Which pair is correctly matched? A. Black powder: high explosive; C-4: low B. Lead azide: primary high; TNT: secondary high C. Mercury fulminate: secondary; RDX: primary D. Semtex: low; TNT: primary Answer: B. Primary: lead azide, fulminate; secondary: TNT, RDX, PETN. (Key point: Examples) 4. Which is a desirable practical property of an explosive for mining? A. Little smoke and no poisonous fumes, cheap and non-hygroscopic B. Absorbs moisture readily C. Produces toxic fumes D. Expensive raw materials Answer: A. Mining explosives should give little smoke and no toxic fumes, and be cheap and non-hygroscopic. 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