How to prove that there is unsaturated hydrocarbon, polyhydric alcohol, aldehyde, carboxylic acid in a test tube.

First you need to find an unsaturated hydrocarbon – it decolours bromine water (Br2). To identify the rest of the substances, one reagent is used – a freshly prepared precipitate of copper hydroxide – Cu (OH) 2:
– in a test tube with acid, it dissolves and a clear blue solution is formed;
– in two other test tubes, when it is dissolved, the solution will be blue;
– test tubes with blue solutions need to be heated – where the solution remains blue – polyhydric alcohol. and in the test tube, where it turns orange, there is an aldehyde.