Redox Reactions റിഡോക്സ് പ്രവർത്തനങ്ങൾ
The chapter opens in the school laboratory. A tiny piece of sodium is dropped into water with a little phenolphthalein: it darts about, fizzes and the water turns pink. Something new has formed. But has anything been lost? Two experiments on an electronic balance show that the total mass does not change in a chemical reaction: this is Lavoisier's law of conservation of mass. Next you will learn to balance chemical equations, so that the same atoms appear on both sides. Then comes the main idea of the chapter. When sodium meets chlorine, sodium loses an electron (oxidation) and chlorine gains it (reduction). The two always happen together, so the reaction is a redox reaction. You will meet oxidising and reducing agents, learn to work out the oxidation number of any atom in a compound, and use it to decide whether a reaction is redox. Rusting, burning, respiration and batteries are all redox reactions. This self-study guide starts from the basics, explains every idea step by step with animations and virtual labs, answers every textbook question, and ends with a revision sheet and a model test.
The chapter in one picture
Part 1 is the law of conservation of mass (മാസ് സംരക്ഷണനിയമം): the hydrogen gas is caught in the balloon, so nothing leaves and the reading stays the same. Part 2 is a redox reaction (റിഡോക്സ് പ്രവർത്തനം): sodium loses an electron (oxidation, ഓക്സീകരണം) and chlorine gains it (reduction, നിരോക്സീകരണം). The small red numbers above the symbols are oxidation numbers (page 7).
How to use this guide
🎬 Watch the animations
Zinc fizzes in acid on a balance, atoms come apart and join up again in new ways, and electrons jump from one atom to another, one step at a time. Press Next ▶ or ▶▶ Auto play. Animations pause by themselves when you scroll away; click a lab to start its clock again.
🧪 Use the virtual labs
An electronic balance, an atom-mass counter, an equation balancer with live atom counts, an electron-transfer sorter, an agent finder, an oxidation-number calculator and a “redox detective”. The dangerous experiments are shown as safe virtual demonstrations.
✍️ Try before you see
Every textbook table is a fill-in table with a check button, and every question hides its answer behind a button. Work it out in your notebook first. The “Check yourself” quizzes at the end of each page tell you at once whether you are right.
📖 Textbook words
Purple മലയാളം words are the exact terms used in your textbook (pages 69–86), so you can match this guide with your book and write answers in either language.
🔇 Quiet and offline
The pages make no sound and need no internet. Optional “Explore online” boxes link to checked websites (no videos); they open only if you click them. Every page is a single file, so the whole guide works on a computer or phone with no connection.
Learning path
Follow the pages in order. If you already read chemical equations easily and remember ions and valency from Chapter 3, you can skim pages 1–2. Still try their quizzes, because the chapter uses these ideas on every page.
Scientist in this chapter
The law that opens this chapter is named after a French chemist. Here he is as a name card (no photo).
Quick glossary (Malayalam ↔ English)
| Textbook term | English | Meaning |
|---|---|---|
| റിഡോക്സ് പ്രവർത്തനങ്ങൾ | Redox reactions | Reactions in which oxidation and reduction take place at the same time |
| രാസപ്രവർത്തനം · രാസമാറ്റം | Chemical reaction · chemical change | A change in which new substances are formed |
| രാസസമവാക്യം | Chemical equation | A reaction written with symbols and formulae: 2H₂ + O₂ → 2H₂O |
| അഭികാരകങ്ങൾ · ഉൽപന്നങ്ങൾ | Reactants · products | The substances that react (left of the arrow) · the substances formed (right of the arrow) |
| ആകെ മാസ് | Total mass | The mass of all the substances taken together |
| മാസ് സംരക്ഷണനിയമം | Law of conservation of mass | In a chemical reaction the total mass of the reactants equals the total mass of the products |
| ഫിനോൾഫ്‌താലീൻ | Phenolphthalein | An indicator: colourless in water and acids, pink in alkalis |
| ഇലക്ട്രോണിക് ബാലൻസ് | Electronic balance | A weighing machine with a digital display, used to find mass accurately |
| അവക്ഷിപ്തം | Precipitate | An insoluble solid that forms when two solutions react (white BaSO₄) |
| ഊർജമാറ്റം | Energy change | Heat, light or electricity given out or taken in during a reaction |
| പ്രതീകാത്മക ചിത്രീകരണം | Symbolic representation | A picture of a reaction with atoms drawn as balls |
| യൂണിഫൈഡ് അറ്റോമിക് മാസ് യൂണിറ്റ് (u) | Unified atomic mass unit | The unit for the masses of atoms: H = 1 u, C = 12 u, O = 16 u |
| രാസസമവാക്യ സമീകരണം | Balancing of chemical equations | Making the number of each kind of atom equal on both sides |
| സമീകൃത രാസസമവാക്യം | Balanced chemical equation | An equation with equal numbers of each kind of atom on both sides |
| ഘട്ടം | Step | One stage of a method (step 1, step 2 …) |
| ഭൗതികാവസ്ഥ · ഉൽപ്രേരകം | Physical state · catalyst | Solid (s), liquid (l), gas (g), solution in water (aq) · a substance that speeds up a reaction without being used up (written over the arrow) |
| ഓക്സീകരണം | Oxidation | Loss of electrons; an increase in oxidation number |
| നിരോക്സീകരണം | Reduction | Gain of electrons; a decrease in oxidation number |
| ഓക്സീകരിക്കപ്പെടുന്നു · നിരോക്സീകരിക്കപ്പെടുന്നു | Is oxidised · is reduced | Loses electrons · gains electrons |
| ഓക്സീകാരി | Oxidising agent | The substance that helps oxidation; it is itself reduced (Cl₂ in 2Na + Cl₂ → 2NaCl) |
| നിരോക്സീകാരി | Reducing agent | The substance that helps reduction; it is itself oxidised (Na in the same reaction) |
| സംയോജകത | Valency | The number of electrons an atom gives, takes or shares when it combines |
| ഓക്സിഡേഷൻ നമ്പർ · ഓക്സീകരണാവസ്ഥ | Oxidation number · oxidation state | The charge an atom would have if all the bonds in the compound were ionic: Na +1, O −2 |
| മൂലകാവസ്ഥ | Elemental state (free state) | An element not joined to any other element (Na, O₂, Cl₂); its oxidation number is 0 |
| ശ്വസനം · ജ്വലനം · വിഘടനം | Respiration · combustion · decomposition | Releasing energy from food in cells · burning · breaking down of dead matter |
| ഓക്സൈഡ് ആവരണം | Oxide layer | A coating of oxide formed on a metal surface, such as rust on iron |
| രാസവൈദ്യുത സെല്ലുകൾ | Electrochemical cells | Cells and batteries that produce electricity from redox reactions |
🌐 Explore online (optional)
Want to go further? The teaching pages end with a few checked websites and simulations (no videos), and page 11 has the full resources hub. They need the internet; the guide itself works offline. To begin, read about calcium carbide, the substance in extended activity 2 (page 10), which your teacher may show:
- 🧪 Balancing Chemical Equations (PhET simulation) PhET, University of Colorado Boulder
Change the coefficients until the atoms on both sides balance; includes a game. - 📄 Chemical equation Wikipedia
How chemical equations are written, with coefficients and states (s), (l), (g), (aq). - 📄 Calcium carbide Wikipedia
The compound in extended activity 2 that gives acetylene gas with water.
Made for self-learning. Works offline – every page is a single file; only the optional "Explore online" links need the internet. Study material prepared by Claude for Madhu's family study folder, October 2026.