b Substances that lose mass when heated i Weigh a testtube containing 1 cm potassium permanganate crystals and a 1 cm plug of cotton wool at the mouth to prevent loss of any solid during heating Heat the testtube and cotton wool and weigh it again Note any change in the potassium permanganate crystals Note any loss in mass due to the loss of water of crystallization ii Weigh a testtube containing 1 cm copper carbonate and a 1 cm plug of cotton wool at the mouth to prevent loss of any solid during heating Heat the testtube and cotton wool and weigh it again Note any change in the copper carbonate Note any loss in mass