Rust: iron's slow fire Lesson 13 of the chemistry course of Mova's primary school: 19 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: the lesson at school .
0 Leave a bike out in the rain all winter and its chain and bolts turn orange-brown and flaky. 1 That orange stuff is rust, a brand-new substance, not dirt that has landed on the metal. 3 Take away either one, the water or the oxygen, and the iron hardly rusts at all. 4 Rusting is a very slow cousin of burning: iron and oxygen join and give out a little heat. 5 In a hand-warmer pack the iron is a fine powder, so it rusts fast enough for you to feel the warmth. 6 Rust is flaky and falls away, so fresh iron underneath is uncovered and rusts next. 7 That is why paint, a coat of zinc or a pinch of chromium mixed into the steel are used to keep air and water off. 8 Other metals change too: copper slowly grows a green coat, like the Statue of Liberty, and that coat stays put and protects the copper underneath. 9 Rust forms when iron or steel joins with oxygen and water; it is a new substance, so rusting is a chemical change. 10 Iron in dry air, or in water with no air in it, hardly rusts; it needs both oxygen and water. 11 In the classic three-nails test, the water is boiled to drive out air and oil is poured on top to stop air getting back in; only the nail in ordinary water with air rusts well. 12 Salt from sea spray or from gritted winter roads makes iron rust faster, so cars and railings by the sea rust quickly. 13 Rust is flaky and falls off, so it does not protect the iron underneath and rusting can go right through. 14 Paint stops rust by keeping air and water away; once the paint is scratched, rust starts at the scratch and creeps under it. 15 Galvanised steel is coated with zinc; the zinc reacts first and "sacrifices" itself, so the iron stays safe even at small scratches, and ships carry zinc blocks for the same reason. 18 The Statue of Liberty is made of copper sheets; it was shiny brown in 1886 and turned green as a protective coat called patina formed. 19 Tetanus is caused by a germ in soil and dirt, not by rust; a deep cut from any dirty object can let it in, and vaccination protects you. 20 Iron is found in rocks mostly joined with oxygen, as iron ore; people heat it with carbon in a furnace to pull the oxygen away and get iron. 21 Mars looks red because its dust contains iron oxide, the same kind of substance as rust. ← previous Fire: what it needs and how to put it outnext → Tarnish and how metals change↑ back to Chemistry This page in Markdown → https://md.mova.elamur.ai/free/en/corpora/school/chemistry/13-rust-irons-slow-fire/