--- title: Tarnish and how metals change — a lesson of Mova's school · trees and pragmatics description: «Tarnish and how metals change», a lesson of the chemistry course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Grandma's best silver spoons come out of the drawer dull and almost black, even though nobody has used them. --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [Chemistry](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/) / Tarnish and how metals change # Tarnish and how metals change Lesson 14 of the chemistry course of Mova's primary school: 18 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](https://md.mova.elamur.ai/free/en/school-run/chemistry/14-tarnish-and-how-metals-change/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/0/) — Grandma's best silver spoons come out of the drawer dull and almost black, even though nobody has used them. - [1](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/1/) — The silver has tarnished: its surface joined with tiny amounts of sulphur gases in the air and made a thin dark layer. - [2](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/2/) — Tarnish is a chemical change on the very surface of a metal. - [3](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/3/) — Silver darkens, copper goes dull brown and then green, and bronze statues in the park grow green streaks. - [4](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/4/) — Not every metal changes. - [5](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/5/) — Gold almost never reacts with air, so gold leaf on an old picture frame still shines after hundreds of years, while some metals, like sodium, react with air within seconds and have to be kept under oil. - [6](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/6/) — Where hands rub a brass door knob or a statue's nose every day, the thin dull layer is rubbed off, and the metal stays bright. - [7](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/7/) — And a clever trick with foil, baking soda and hot water can even turn the black tarnish on silver back into silver. - [8](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/8/) — Silver tarnishes because it reacts with sulphur gases in the air and makes a thin black layer. - [9](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/9/) — Eggs, onions and some rubber give off sulphur gases, so silver egg spoons tarnish very quickly. - [10](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/10/) — In hot water with baking soda, aluminium foil takes the sulphur back from the tarnish and turns it back into silver; the water is hot, so it is a grown-up's job. - [12](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/12/) — Copper slowly reacts with air and goes dull brown; vinegar with a pinch of salt makes a dull coin shiny again. - [13](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/13/) — A cheap ring with copper in it can leave a harmless green mark on skin, because sweat with its salt and acid reacts with the copper; the mark simply washes off. - [15](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/15/) — Oxygen is a very reactive gas; a cut apple and a cut piece of some metals both change colour in air, in very different ways. - [16](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/16/) — Sodium metal reacts with air within seconds, so laboratories keep it under oil. - [18](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/18/) — Gold almost never reacts with oxygen or sulphur, so it does not tarnish and is used on domes and picture frames. - [19](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/19/) — Cola has a weak acid that slowly loosens rust on a nail; the story that cola dissolves a tooth overnight is a myth, though sugary acid drinks do harm teeth over time. - [20](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/14-tarnish-and-how-metals-change/20/) — Carbon steel knives (not stainless) get dark spots when left wet with acid such as vinegar, so chefs dry them at once. - ← previous: [Rust: iron's slow fire](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/13-rust-irons-slow-fire/) - next →: [Acids in the kitchen](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/15-acids-in-the-kitchen/) - ↑ back to [Chemistry](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/)