Each student encounters in physics lessons with such a thing as "specific heat". In most cases, people forget the school definition, and often do not understand the meaning of this term. In technical universities, most students will sooner or later encounter specific heat. Perhaps, within the framework of the study of physics, or maybe someone will have such a discipline as "heat engineering" or "technical thermodynamics." In this case, you have to remember the school curriculum. So, below we consider the definition, examples, values for some substances.
Definition
Specific heat is a physical quantity that characterizes how much heat needs to be brought to a unit of substance or removed from a unit of substance so that its temperature changes by one degree. It is important to cancel, which does not matter, degrees Celsius, Kelvin and Fahrenheit, the main thing is the change in temperature by one.
Specific heat has its own unit of measurement - in the international system of units (SI) - Joule, divided by the product of kilogram and Kelvin degree, J / (kg · K); an off-system unit is the ratio of calories to the product of kilogram and degree Celsius, cal / (kg · ° C). This value is most often indicated by the letter C or C, sometimes indexes are used. For example, if the pressure is constant, then the index p, and if the volume is constant, then v.
Variations of Definition
Several formulations of the definition of the discussed physical quantity are possible. In addition to the above, the definition that states that the specific heat is the ratio of the heat capacity of a substance to its mass is considered acceptable. In this case, it is necessary to clearly understand what "heat capacity" is. So, heat capacity is a physical quantity that shows how much heat needs to be brought to the body (substance) or removed in order to change its temperature by one. The specific heat capacity of a mass of a substance greater than a kilogram is determined in the same way as for a single value.
Some examples and meanings for various substances
It was experimentally found that for different substances this value is different. For example, the specific heat of water is 4.187 kJ / (kg · K). The largest value of this physical quantity in hydrogen is 14.300 kJ / (kg · K), the smallest - in gold, is 0.129 kJ / (kg · K). If you need a value for a specific substance, then you need to take a directory and find the appropriate tables, and in them - the values of interest. However, modern technologies make it possible to speed up the search process by several times - it is enough on any phone that has the option of accessing the world wide Internet, type the question in the search bar, start the search and search for the answer based on the results. In most cases, you must follow the first link. However, sometimes you don’t need to go anywhere else at all - the answer to the question is visible in a brief description of the information.
The most common substances for which specific heat is being sought, including specific heat, are:
- air (dry) - 1.005 kJ / (kg · K),
- aluminum - 0.930 kJ / (kg · K),
- copper - 0.385 kJ / (kg · K),
- ethanol - 2.460 kJ / (kg · K),
- iron - 0.444 kJ / (kg · K),
- mercury - 0.139 kJ / (kg · K),
- oxygen - 0.920 kJ / (kg · K),
- wood - 1,700 kJ / (kg · K),
- sand - 0.835 kJ / (kg · K).