text: The pH scale measures the acidity of a substance.\n\npH 7 is neutral. De-ionised water has a pH of 7.\n\na pH less than 7 (i.e 0 to 6.9) indicates an acidic substance. (Such as vinegar)\n\na pH greater than 7 (i.e 7.1 to 14 (the scale ends at 14)) indicates an alkali substance (think of alkali as opposite to acid). Alkaline is also know as basic.\n\nHope this helps