Masses and Exothermic Reactions

Problem Pupils may have the opinion that there is such a thing as heat matter , or that different samples of energy exhibit different masses. In an exothermic reaction, the involved substances should have to lose a portion of their mass - the law on conservation of mass in chemical reactions would not apply in this case. In order to remind students of this law, an exothermic reaction should be quantitatively introduced. 

Material Test tubes, balloon, balances matches. 

Procedure Place several match heads in a test tube, close it with a balloon and weigh it. Heat the test tube with the hottest flame of the burner until match heads are lit. After cooling down weigh the test tube and content once more. 

Observation The masses are identical the energy portion that is released as thermal energy and light energy has no mass. 

Problem Apart from misconceptions on heat matter , it is the origin of energy or consumption of energy which pupils encounter in everyday 

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