Applications & Explore Online റിഡോക്സ് പ്രവർത്തനങ്ങൾ

Redox reactions are not only in the laboratory. The iron gate rusting in the salty sea breeze, the firewood in the kitchen hearth, your breathing after a football match, the banana leaves rotting in the compost pit, the torch battery, the bleaching powder in the village well, the iron in a bicycle and the silver in an old photograph: in every one of them some atoms lose electrons and others gain them. Every section has a small animation and a sample exam question. The page ends with a hub of links to explore online.

1. Rusting of iron gates and fishing boats, and how to stop it

Near the coast, iron gates, window grills, bicycle chains and the iron parts of fishing boats turn reddish-brown and flaky very quickly. This is rusting. Iron combines with oxygen from the air in the presence of moisture; salt in the sea breeze makes it faster. Each iron atom loses electrons (oxidation) and each oxygen atom gains them (reduction): rusting is a redox reaction that forms an oxide layer ഓക്സൈഡ് ആവരണം. The textbook equation is 4Fe + 3O₂ → 2Fe₂O₃. To stop it, we keep air and water away: paint on gates, oil or grease on chains and tools, and a coat of zinc on galvanised iron (GI) sheets for roofs. go further Real rust also contains water (hydrated iron oxide); zinc protects even where the coat is scratched, because zinc is oxidised in place of the iron.

2. Firewood in the hearth, biogas and LPG: combustion

When firewood burns in the kitchen hearth അടുപ്പ്, its carbon combines with oxygen of the air and gives out heat and light. Burning, or combustion ജ്വലനം, is a redox reaction. Take carbon (charcoal) as the fuel: C + O₂ → CO₂. Carbon goes from 0 to +4 (oxidised; it is the reducing agent); oxygen goes from 0 to −2 (reduced; it is the oxidising agent), exactly as in Table 4.9. Methane, the main gas in biogas plants, burns the same way: CH₄ + 2O₂ → CO₂ + 2H₂O. The LPG in the cooking cylinder (mainly butane and propane) also burns to carbon dioxide and water. go further The wood seems to lose mass only because the CO₂ and water vapour fly away (page 3).

3. Respiration: where the energy for a football match comes from

After a football match you breathe fast and deep. Your muscles need energy, and they get it from respiration ശ്വസനം: in the cells, glucose from food is broken down with the oxygen you breathe in, giving carbon dioxide, water and energy. Lavoisier showed that respiration takes in oxygen and gives out carbon dioxide, like a slow burning. It is a redox reaction: the carbon of glucose is oxidised and the oxygen is reduced. go further The overall equation is C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy. In glucose the average oxidation number of carbon is 0 (6x + 12 − 12 = 0); in CO₂ it is +4.

4. Banana leaves in the compost pit: decomposition in oxygen

Banana leaves, vegetable peels and dry leaves thrown into a compost pit slowly turn into dark, crumbly manure. Tiny living things, bacteria and fungi, decompose വിഘടനം the organic matter, using oxygen from the air. The carbon is oxidised to carbon dioxide, and heat is given out (a good compost heap feels warm inside). That is why farmers turn the heap now and then: it lets air in. Decomposition of organic matter in oxygen is one of the redox reactions named in the textbook. go further A cut apple or banana going brown is also an oxidation by the oxygen of air, helped by substances in the fruit; lemon juice slows it down.

5. Torch and mobile batteries: electricity from redox

A torch cell (dry cell) and a mobile phone battery are electrochemical cells രാസവൈദ്യുത സെല്ലുകൾ. Inside, a redox reaction is split into two halves at two different places. In a dry cell the zinc case is oxidised, Zn → Zn²⁺ + 2e⁻; the electrons cannot jump straight across, so they travel through the wire and the bulb to the carbon rod, where another substance (manganese dioxide) is reduced. That flow of electrons is the electric current. go further In a mobile phone's lithium-ion battery, lithium atoms give up electrons while the phone is used: Li → Li⁺ + e⁻; charging pushes the reaction back.

6. Bleaching powder in the well: oxidising agents that kill germs

After a flood, or before the monsoon, health workers add a measured amount of bleaching powder to wells. It releases chlorine, which acts as an oxidising agent ഓക്സീകാരി: it takes electrons from the substances in germs and in coloured stains, destroying them. While it oxidises them, the chlorine itself is reduced to chloride ions: Cl + 1e⁻ → Cl⁻ (oxidation number 0 → −1). Purple potassium permanganate (KMnO₄) is another strong oxidising agent used to disinfect; its manganese has oxidation number +7 (page 7) and is reduced when it reacts. Bleaching of cloth and paper also works by oxidation.

7. Getting iron from its ore: reduction with carbon go further

Iron is found in the earth as an ore, mainly iron oxide (Fe₂O₃), with iron at +3. To get the metal, the iron ions must gain electrons: the ore must be reduced. In a blast furnace the ore is heated strongly with coke (carbon). Carbon takes away the oxygen and is itself oxidised: 2Fe₂O₃ + 3C → 4Fe + 3CO₂. Here carbon is the reducing agent നിരോക്സീകാരി. (In the real furnace much of the work is done by carbon monoxide, CO, made from the coke.) Rusting and extraction are the same change run in opposite directions: rusting oxidises iron to its oxide, the furnace reduces the oxide back to iron.

8. Silver in old photographs go further

Before digital cameras, black-and-white photographs were made on film coated with a silver compound containing silver ions, Ag⁺. Where light fell on the film, and then in the developer solution, the silver ions gained electrons and became tiny grains of black silver metal: Ag⁺ + e⁻ → Ag. This is exactly the example in the textbook of a positive ion being reduced. The bright parts of the scene became dark on the film (a “negative”). Silver ornaments slowly going dull and dark is the opposite change: silver reacting with sulphur compounds in the air, an oxidation.

🌐 Explore online – resources hub

Everything in this guide works offline. The links below are extras: a simulation and articles from trusted sources (PhET, Wikipedia), grouped by topic. They need internet and open in a new tab, so you will not lose your place here. Ask a parent or teacher before you go online. The PhET simulations run directly in the browser, with nothing to install.

Conservation of mass and Lavoisier

Balancing chemical equations

Oxidation, reduction and redox

Oxidation number

Redox reactions in daily life

More to explore