Thermochemistry

How can thermal energy be measured? One way is to measure a quantity called the specific heat. The specific heat of a substance is the amount of thermal energy required to heat one gram of that substance by one degree. Once again, the specific heat of a substance is an intensive property, meaning that it does not depend on the amount of substance present. The specific heat of a drop of water and a pan of water are the same. When we multiply the mass of an object by its specific heat, it is possible to calculate the heat capacity of that object. Heat capacity is an extensive property, meaning that it is dependent on the quantity of substance present. The heat capacity of a drop of water is much, much less than that of a lake. The specific heat of water is unusually high compared to many other substances. This fact has an important impact on us. Cities located near huge bodies of water tend to have more moderate climates. Such cities are cooler in the summer as large water bodies take a long time to absorb the heat of the summer sun, and these cities are warmer in the winter, as the water slowly releases the heat it had absorbed during the summer. Since our bodies are composed largely of water, we are able to maintain a fairly constant body temperature, in spite of outside temperature fluctuations. Even so, one important fact arises from all the information so far. We cannot measure an absolute value for energy. We can, however, measure energy differences.