Glass and pottery Lesson 30 of the chemistry course of Mova's primary school: 17 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 A window pane is made of sand. 1 Sand is melted with soda and crushed limestone in a furnace hotter than 1000 °C, and the glowing runny glass is cooled into sheets, bottles and jars. 2 When glass cools, its particles do not have time to line up in neat crystals; they freeze in a jumble, so glass is a hard solid that breaks with smooth, razor-sharp edges. 3 Hot glass is soft like toffee: a glassblower blows into a blob of it on a long pipe and it swells into a bubble that becomes a vase. 4 Nature makes glass too, when lightning strikes sand or lava cools very fast. 5 Pottery is different: soft clay is shaped and then baked in a very hot oven called a kiln until it turns hard as stone. 6 A shiny glaze, which is a thin coat of glass, makes a mug waterproof. 8 In glass the particles are frozen in a jumble instead of neat crystals; old windows that are thicker at the bottom were made that way, glass does not slowly flow down. 9 Glassblowers shape glass that is over 1000 °C, when it is soft and stretchy. 10 Oven glass expands very little when heated, so it does not crack in the oven; ordinary glass can crack when heated or cooled unevenly, for example a hot dish put into cold water. 11 Lightning striking sand can melt it into glass tubes called fulgurites; volcanoes make a natural black glass called obsidian. 13 Broken glass splits into thin, sharp edges, so it is swept up carefully with a brush and dustpan, never picked up with bare hands. 14 Car side and back windows are toughened to crumble into small blunt pieces; the windscreen has a layer of plastic inside, so it cracks but holds together. 15 Pottery is clay baked in a kiln at a very high heat, which makes it hard for good; a glaze is a thin glass coating that makes it waterproof; a clay pot must dry out fully before firing, or the water inside turns to steam and can crack it. 16 Glass can be melted and made into new bottles again and again without wearing out, and melting old glass needs less energy than making it from sand. 17 Phone screens are toughened glass, treated so the surface is harder; a drop on a corner can still crack them. 18 Optical fibres are thin strands of glass that carry light along bends, because the light keeps bouncing inside the fibre; most of the internet travels through such fibres, even under the oceans. ← previous Plastics: useful and stubbornnext → Metals and what they're good for↑ back to Chemistry This page in Markdown → https://md.mova.elamur.ai/free/en/corpora/school/chemistry/30-glass-and-pottery/