313_Chemistry_Eng_Lesson31.pdf). Content covers sections 31.1–31.6.Soaps and detergents clean by acting as surfactants (surface-active agents). Polymers — giant molecules from repeating monomers — shape modern life: packaging, textiles, tyres, medical devices. This lesson covers cleansing chemistry, polymer types, commercial plastics and rubbers, and biodegradable alternatives.
Both concentrate at the water surface/interface, lower surface tension, foam, emulsify grease and remove dirt. Molecules have two parts:
By charge of the head: anionic (most common), cationic or non-ionic.
Soaps: sodium or potassium salts of long-chain fatty acids from oils/fats (glycerides of palmitic, stearic acids, etc.).
Saponification: fat/oil + NaOH (or KOH) → soap (3 RCOONa) + glycerol. Classic industrial route from vegetable or animal fats.
Synthetic detergents: e.g. sodium salts of long-chain alkyl hydrogen sulphates (sodium lauryl sulphate C₁₂H₂₅OSO₃Na) or alkylbenzene sulphonates. Same head–tail design as soap, different polar group.
In water, soap/detergent ions associate into micelles above the critical micelle concentration (CMC) and above the Kraft temperature. Hydrophobic tails point inward; hydrophilic heads face water. Grease is taken into the non-polar core; mechanical action forms an emulsion that rinses away. Micelles are colloidal-scale aggregates of many small surfactant molecules.
Advantage: detergents work in hard water — Ca²⁺/Mg²⁺ salts of detergent anions stay soluble. Soap forms insoluble scum (calcium/magnesium carboxylates) and loses lather.
Disadvantage: branched alkylbenzene sulphonates are only partly biodegradable (~50–60%) → water/soil pollution. Linear alkylbenzene sulphonates (~90%) and lauryl sulphate (~100%) are better. Soap is fully biodegradable.
A polymer is a high-mass macromolecule from many monomers linked together. Example: ethene → polyethene –(CH₂–CH₂)ₙ–.
Homopolymer: one monomer type (polyethene). Copolymer: two or more (Buna-S from butadiene + styrene).
Addition (chain-growth) polymerisation: unsaturated monomers add without eliminating a small molecule; needs an initiator (e.g. free radical from benzoyl peroxide). Stages: initiation → propagation → termination. Examples: polyethene, PVC, polystyrene.
Condensation (step-growth) polymerisation: monomers with two functional groups combine with loss of H₂O, NH₃, etc. Molecular mass is not a simple multiple of monomers. Examples: terylene, nylon-66, bakelite.
By origin: natural (starch, cellulose, rubber, proteins) vs synthetic (nylon, PVC, bakelite, terylene).
By structure: linear (high density, strength — nylons, polyesters); branched (LDPE, starch — lower packing); cross-linked 3D network (bakelite, melamine — hard, rigid).
By polymerisation method: addition vs condensation polymers (as above).
By intermolecular forces:
Natural rubber: polymer of isoprene (2-methylbuta-1,3-diene) from latex. Soft, sticky, narrow useful T range, poor solvent resistance when raw.
Vulcanisation (Goodyear): heat with sulphur (or S₂Cl₂) → S cross-links between chains. Improves hardness, tensile strength, elasticity, wear resistance; wider T range (−40 to 100 °C); less sticky; insoluble in common solvents. Amount of S, temperature and time control hardness.
Synthetic rubbers:
Polyolefins & vinyls: polyethene (LDPE branched vs HDPE linear compact); polypropylene (Ziegler–Natta); Teflon (PTFE) from CF₂=CF₂ — non-stick, chemical resistant; PVC from vinyl chloride — pipes, raincoats, insulation (plasticized for flexibility); PMMA (Perspex/Lucite) — transparent glass substitute.
Polyesters: Terylene/Dacron — ethylene glycol + terephthalic acid; wash-and-wear fibres. Glyptal — glycol + phthalic acid; paints, lacquers (cross-linked resins).
Polyamides: Nylon-66 — hexamethylenediamine + adipic acid; fibres, ropes, carpets, bristles. Nylon-6 — from caprolactam.
Thermosets: bakelite (phenol–formaldehyde) — electrical fittings; urea/melamine–formaldehyde — crockery, laminates.
Biopolymers (natural): starch and cellulose (glucose polymers); proteins (amino acids); nucleic acids (nucleotides) — life processes (links L29).
Most commodity plastics resist light, water and microbes → disposal problem. Mitigate by reuse, recycling, remoulding, limited depolymerisation. Better: design biodegradable polymers with enzyme-cleavable links (often ester groups) so soil microbes can break them down.
PHBV — copolymer of 3-hydroxybutanoic and 3-hydroxypentanoic acids (ester links); stiffness/flexibility tuned by ratio; orthopaedic devices, controlled drug release.
PGA (polyglycolic acid), PLA (polylactic acid), PCL (poly-ε-caprolactone) — medical sutures, agricultural films, packaging, hygiene products. Cost still limits everyday replacement of PE/PVC, but use is growing.
High-yield: head–tail structure; saponification; micelle cleaning; soap vs detergent in hard water; linear vs branched ABS biodegradability; monomer/polymer definitions; addition vs condensation table; thermoplastic vs thermoset; vulcanisation benefits; monomers of PE, PVC, teflon, nylon-66, terylene, Buna-S, neoprene, natural rubber; PHBV uses.
Completes Module 8 everyday chemistry after organic Module 7 (L23–L29). Review monomer tables and comparison charts before exams — they appear almost every year.
Most exam-important points from this chapter:
Head–tail amphiphiles. Soap = RCOONa. Detergent works in hard water. Micelles clean. Prefer linear ABS.
Monomer → polymer. Homo vs co. Addition (chain) vs condensation (step). Natural vs synthetic.
Linear/branched/cross-linked. Elastomer · fibre · thermoplastic · thermoset. Plasticizers soften PVC.
Memorise monomers: PE, PVC, teflon, PMMA, nylon-66, terylene, Buna-S, neoprene, isoprene rubber.
Vulcanise with S. Biodegradable: PHBV, PLA, PGA — ester links, medical/packaging uses.
Extracted from NIOS Chemistry (313) board exam papers in your PDF. Chapter L31 — Soap, Detergents and Polymers only. Use Model Answer for marking points; Explanation for concept clarity.
12 question(s) · Sources: 313/MAY/205A, 313/MAY/205B, 313/MAY/205C, 313/TUS/105A
PYQ1. High-density polymers with high tensile strength and high melting points are — (A) linear polymers (B) natural polymers (C) branched chain polymers (D) cross-linked polymers Cƒ VZZ e{º
Model Answer
Model approach (select the best option):
Eliminate options that contradict definitions/equations from the chapter notes. NIOS awards full mark for the single correct choice.
Explanation
This MCQ belongs to L31. Recall the core definition or formula from notes, then match it to one option. Paper: 313/MAY/205A · Q15.
Tip: For numerical MCQs, write the formula first, substitute values, then pick the option.
PYQ2. The monomer unit of polyvinylchloride (PVC) is — (A) CH3CH2Cl (B) CH2=CH—Cl (C) CH3CHCl (D) ClCH=CHCl nm°br{dZmBb³bmoamBS> (PVC)
Model Answer
Model approach (select the best option):
Eliminate options that contradict definitions/equations from the chapter notes. NIOS awards full mark for the single correct choice.
Explanation
This MCQ belongs to L31. Recall the core definition or formula from notes, then match it to one option. Paper: 313/MAY/205A · Q16.
Tip: For numerical MCQs, write the formula first, substitute values, then pick the option.
PYQ3. Read the passage given below and answer the following questions : The molecules of soaps and detergents are smaller than the colloidal particles. These molecules associate and get the colloidal particle size range. These are called micelles. They also dissociate in ions on dissolving in water as they are electrolytic in nature. When soap is used for cleaning purposes, which part of it is directed towards the centre of the micelle? Why are micelles absorbed by grease in cloth?
Model Answer
Give the chemical reason linked to structure/bonding/equilibrium. Start with the principle, then apply to the species named in the question.
Explanation
Reasoning marks require principle + application. Cite electron effects, stability, or Le Chatelier as relevant.
How to write for NIOS: Use 30–50 words (VSA) or short objective. Open with definition/equation, then reason, end with conclusion. Paper 313/MAY/205A · Q28 · 2 mark(s) · L31.
PYQ4. High-density polymers with high tensile strength and high melting points are — (A) linear polymers (B) natural polymers (C) branched chain polymers (D) cross-linked polymers Cƒ VZZ e{º
Model Answer
Model approach (select the best option):
Eliminate options that contradict definitions/equations from the chapter notes. NIOS awards full mark for the single correct choice.
Explanation
This MCQ belongs to L31. Recall the core definition or formula from notes, then match it to one option. Paper: 313/MAY/205B · Q6.
Tip: For numerical MCQs, write the formula first, substitute values, then pick the option.
PYQ5. The monomer unit of polyvinylchloride (PVC) is — (A) CH3CH2Cl (B) CH2=CH—Cl (C) CH3CHCl (D) ClCH=CHCl nm°br{dZmBb³bmoamBS> (PVC)
Model Answer
Model approach (select the best option):
Eliminate options that contradict definitions/equations from the chapter notes. NIOS awards full mark for the single correct choice.
Explanation
This MCQ belongs to L31. Recall the core definition or formula from notes, then match it to one option. Paper: 313/MAY/205B · Q7.
Tip: For numerical MCQs, write the formula first, substitute values, then pick the option.
PYQ6. Read the passage given below and answer the following questions : The molecules of soaps and detergents are smaller than the colloidal particles. These molecules associate and get the colloidal particle size range. These are called micelles. They also dissociate in ions on dissolving in water as they are electrolytic in nature. When soap is used for cleaning purposes, which part of it is directed towards the centre of the micelle? Why are micelles absorbed by grease in cloth?
Model Answer
Give the chemical reason linked to structure/bonding/equilibrium. Start with the principle, then apply to the species named in the question.
Explanation
Reasoning marks require principle + application. Cite electron effects, stability, or Le Chatelier as relevant.
How to write for NIOS: Use 30–50 words (VSA) or short objective. Open with definition/equation, then reason, end with conclusion. Paper 313/MAY/205B · Q19 · 2 mark(s) · L31.
PYQ7. The monomer unit of polyvinylchloride (PVC) is — (A) CH3CH2Cl (B) CH2=CH—Cl (C) CH3CHCl (D) ClCH=CHCl nm°br{dZmBb³bmoamBS> (PVC)
Model Answer
Model approach (select the best option):
Eliminate options that contradict definitions/equations from the chapter notes. NIOS awards full mark for the single correct choice.
Explanation
This MCQ belongs to L31. Recall the core definition or formula from notes, then match it to one option. Paper: 313/MAY/205C · Q6.
Tip: For numerical MCQs, write the formula first, substitute values, then pick the option.
PYQ8. High-density polymers with high tensile strength and high melting points are — (A) linear polymers (B) natural polymers (C) branched chain polymers (D) cross-linked polymers Cƒ VZZ e{º
Model Answer
Model approach (select the best option):
Eliminate options that contradict definitions/equations from the chapter notes. NIOS awards full mark for the single correct choice.
Explanation
This MCQ belongs to L31. Recall the core definition or formula from notes, then match it to one option. Paper: 313/MAY/205C · Q16.
Tip: For numerical MCQs, write the formula first, substitute values, then pick the option.
PYQ9. Read the passage given below and answer the following questions : The molecules of soaps and detergents are smaller than the colloidal particles. These molecules associate and get the colloidal particle size range. These are called micelles. They also dissociate in ions on dissolving in water as they are electrolytic in nature. When soap is used for cleaning purposes, which part of it is directed towards the centre of the micelle? Why are micelles absorbed by grease in cloth?
Model Answer
Give the chemical reason linked to structure/bonding/equilibrium. Start with the principle, then apply to the species named in the question.
Explanation
Reasoning marks require principle + application. Cite electron effects, stability, or Le Chatelier as relevant.
How to write for NIOS: Use 30–50 words (VSA) or short objective. Open with definition/equation, then reason, end with conclusion. Paper 313/MAY/205C · Q18 · 2 mark(s) · L31.
PYQ10. The polymer which becomes soft on heating or becomes rigid on cooling is known as — (A) elastomer (B) fibre (C) thermosetting (D) thermoplastic Omo
Model Answer
Model approach (select the best option):
Eliminate options that contradict definitions/equations from the chapter notes. NIOS awards full mark for the single correct choice.
Explanation
This MCQ belongs to L31. Recall the core definition or formula from notes, then match it to one option. Paper: 313/TUS/105A · Q15.
Tip: For numerical MCQs, write the formula first, substitute values, then pick the option.
PYQ11. The washing material which is 100% biodegradable and contains carboxylate ion is — (A) soap (B) branched alkyl benzene sulphonate (C) linear alkyl benzene sulphonate (D) lauryl alcohol YmoZo
Model Answer
Model approach (select the best option):
Eliminate options that contradict definitions/equations from the chapter notes. NIOS awards full mark for the single correct choice.
Explanation
This MCQ belongs to L31. Recall the core definition or formula from notes, then match it to one option. Paper: 313/TUS/105A · Q16.
Tip: For numerical MCQs, write the formula first, substitute values, then pick the option.
PYQ12. Read the passage given below and answer the following questions (out of four attempt any two) : A polymer is a giant molecule formed by intermolecular linkage between same or different types of smaller molecules called monomers. The process by which the monomers get linked up is called polymerization. The polymers can be classified on the basis of origin, structure, method of polymerization and molecular forces. What are the monomers of Terylene? Among Buna-S and Neoprene, which one is a copolymer and why? In which process of polymerization are by-products obtained? In which categories are polymers classified based on their structure?
Model Answer
State the precise definition from the L31 notes in 1–2 sentences, include formula/example if marks ≥ 2, and avoid extra theory beyond the ask.
Explanation
Definition questions score for accuracy of wording + one supporting point/example. Do not write full chapter summaries.
How to write for NIOS: Use 30–50 words (VSA) or short objective. Open with definition/equation, then reason, end with conclusion. Paper 313/TUS/105A · Q28 · 2 mark(s) · L31.
Six problems spanning this chapter’s NIOS syllabus. Every question is built from the notes and formula sheet: solve with equations first, then read the formal textbook-style write-up, the easy explanation, and the topic in depth (formulas, meaning, exam tips). If the question says draw, a labelled pencil sketch is provided. Explanations open by default.
What is saponification?
Final answer: Fat + NaOH → soap + glycerol
Soaps are sodium/potassium salts of long-chain fatty acids.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Boil oil with NaOH—get soap and glycerine.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
Hard water precipitates Ca/Mg soaps.
Linked to chapter notes (L31). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.
Why do detergents work better in hard water than soaps?
Final answer: No insoluble Ca/Mg scum
Synthetic detergents are effective cleansing agents in hard water.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Detergent heads stay dissolved even with hard-water ions.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
Can be anionic, cationic, non-ionic.
Linked to chapter notes (L31). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.
Draw the polymerisation idea of ethene to polyethylene.
Final answer: Polyethylene from ethene
Addition polymers form by chain reaction of unsaturated monomers.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Double bonds open and link into a long chain.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
No small molecule eliminated.
Linked to chapter notes (L31). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.
Give one example of a condensation polymer and monomers.
Final answer: e.g. nylon-6,6
Condensation polymers eliminate small molecules (H₂O, HCl).
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Two different ends react and spit out water while chaining.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
Bakelite is a thermosetting condensation polymer.
Linked to chapter notes (L31). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.
What is the monomer of natural rubber?
Final answer: Isoprene
Natural rubber is cis-polyisoprene.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Plant latex polymer of isoprene units.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
Vulcanisation with S improves elasticity.
Linked to chapter notes (L31). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.
Why are biodegradable polymers desirable?
Final answer: Environmental degradation / less pollution
Designed to break down after use.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Plastics that nature can digest after disposal.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
Examples: PHBV, polyglycolic acid (as taught).
Linked to chapter notes (L31). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.