Tamar Class investigated a range of different solids to find out if they would dissolve. The powders were kept secret until the end of the investigation, but I can reveal there was: sugar, salt, powdered milk, cement, cornflour, sand, polyfilla and cellulose glue.
First they observed the powders closely, noticing their texture, grain size, colour smell and even sound! They predicted whether each solid might dissolve, then they mixed each solid with 100ml of water to find out if they would dissolve. They observed the effects of mixing with wate closely and noticed that some solids dissolved completely, some simply sand and departed while others changed without dissolving. Great science, Tamar.