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Left: Heat crystals from grape jelly  in a high ampoule with a syringe full of water. Wait until the crystals have disappeared.
Middle: Add drops of water to each sample of  sugar (Zucker), salt (Salz) and citric acid (Zitronensäure).
             Stir carefully until all the crystals are dissolved.
Right: Sugar, salt and acid are no longer visible. (Some salt samples leave a cloudy liquid).
The disappearing of sugar and citric acid in a liquid is called dissolving.