--- title: Indicators: the red-cabbage rainbow — a lesson of Mova's school · trees and pragmatics description: «Indicators: the red-cabbage rainbow», a lesson of the chemistry course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Chop red cabbage, soak it in hot water, and you get a purple juice. --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/) [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/) / Indicators: the red-cabbage rainbow # Indicators: the red-cabbage rainbow Lesson 17 of the chemistry course of Mova's primary school: 21 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/17-indicators-the-red-cabbage-rainbow/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/0/) — Chop red cabbage, soak it in hot water, and you get a purple juice. - [1](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/1/) — Add a splash of vinegar and it turns pink; add a pinch of baking soda and it turns blue-green. - [2](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/2/) — The juice is an indicator: a colour that tells you whether something is an acid or an alkali. - [3](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/3/) — Inside the cabbage is a colour substance whose tiny particles change shape in acid or alkali, and a different shape means a different colour. - [4](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/4/) — Blueberries hold the same kind of colour, which is why blueberry pancakes with too much baking soda get green streaks. - [5](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/5/) — Scientists use indicators too: litmus paper, made from lichens, turns red in acid and blue in alkali. - [6](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/6/) — Universal indicator mixes several dyes, so each pH gets its own colour, a whole rainbow from red to purple. - [7](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/7/) — Indicators hide in everyday life: lemon makes tea paler, a curry stain turns red when washed with soap, and pool keepers check the water every day with drops and a colour card. - [8](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/8/) — An indicator is a substance whose colour shows whether something is acidic or alkaline. - [9](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/9/) — Red cabbage juice is purple in neutral water, pink-red with acid, blue-green with a mild alkali like baking soda, and yellow with a very strong alkali. - [10](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/10/) — The colour substance in red cabbage changes shape at different pH, and each shape has a different colour. - [11](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/11/) — Blueberries have the same kind of colour substance, so they turn greenish in batter with too much baking soda; a little lemon juice brings the purple back. - [12](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/12/) — Litmus paper turns red in acid and blue in alkali; its dye comes from lichens and has been used for hundreds of years. - [13](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/13/) — Tea's colour substances change in acid: lemon makes tea paler, and baking soda makes it darker. - [14](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/14/) — Beetroot juice stays red in vinegar and turns more purple-brown in alkali; not every plant colour changes the same way. - [15](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/15/) — Beetroot can make your wee pink, which is harmless. - [16](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/16/) — Universal indicator is a mix of several indicators; each changes at a different point, so together they give a different colour for each pH. - [17](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/17/) — Scientists also use electronic pH meters. - [18](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/18/) — Yellow turmeric turns reddish-brown with an alkali, so a curry stain can turn red when washed with soap. - [19](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/19/) — Pool test kits compare the colour of a water sample with drops added to a colour card; water that is too acidic stings the eyes. - [20](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/17-indicators-the-red-cabbage-rainbow/20/) — Lemon-juice writing is invisible until a grown-up warms the paper, when the juice turns brown before the paper does; spies once used invisible inks like this. - ← previous: [Alkalis and soda, and how they cancel acids](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/16-alkalis-and-soda/) - next →: [The fizz: vinegar, lemon and soda](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/18-the-fizz-vinegar-lemon-and-soda/) - ↑ back to [Chemistry](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/)