Liquid heat-energy graph

The graph in Figure 11-37 shows that adding heat to boiling water does not cause the temperature of the water to increase. Instead, the added energy is used to overcome intermolecular attractions as molecules leave the liquid phase and enter the gas phase. Other two-phase systems, such as an ice-water mixture, show similar behavior. 

Temperature again increases during interval C on the graph. Energy is being absorbed by the liquid water molecules. Notice that the slope of the line during this interval is different than the slope of the line during interval A. This is due to differences in the heat capacity of ice and liquid water. 

In this method, the sonication cell acts as a calorimeter containing a volume V of liquid irradiated with ultrasound during a time At. The mechanical energy is reduced to heat, and the rise in temperature AT is measured and entered upon a graph as a function of At. In the linear part of the graph, the slope AT/At is deduced and put into Eq. 7 6... 

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