17 ENERGY FROM CHEMICAL REACTIONS The following group of reactions involve ions in aqueous solution When the water containing the reacting ions becomes hotter then we have gained this heat and we can make it do work for us During the reaction the ions have lost this heat which we have gained On the other hand when the water containing the ions becomes colder it is the ions which have gained the energy and the water has lost an equivalent amount a REACTIONS THAT GIVE OUT HEAT ENERGY Be careful The reaction is vigorous so do not do the experiment in a stoppered bottle i Put white anhydrous copper sulphate powder to a depth of about 1 cm in a testtube Hold a thermometer with the bulb in the powder Add water drop by drop Record the changes of the thermometer reading ii Put about 10 mL of strong aqueous copper sulphate solution into a wide testtube or small beaker Support a thermometer with the bulb in the solution Add magnesium powder or ribbon a little at a time until the blue colour disappears Note any changes in the thermometer reading iii To a little water in a wide testtube add concentrated sulphuric acid drop by drop down the side of the tube Stir gently with a thermometer after the addition of each drop Note any changes in the thermometer reading