Every schoolchild comes across such a concept as "specific heat capacity" in physics lessons. In most cases, people forget the school definition, and often do not understand the meaning of this term at all. In technical universities, most students will sooner or later encounter specific heat. Perhaps, as part of the study of physics, or maybe someone will have such a discipline as "heat engineering" or "technical thermodynamics". In this case, you will have to remember the school curriculum. So, below is the definition, examples, meanings for some substances.
Definition
Specific heat capacity is a physical quantity that characterizes how much heat must be supplied to a unit of a substance or removed from a unit of a substance in order for its temperature to change by one degree. It is important to cancel that it doesn't matter if Celsius, Kelvin or Fahrenheit, the main thing is the change in temperature per unit.
Specific heat capacity has its own unit of measurement - in the international system of units (SI) - Joule divided by the productkilograms and degrees Kelvin, J / (kg K); the off-system unit is the ratio of a calorie to the product of a kilogram and a degree Celsius, cal/(kg °C). This value is most often denoted by the letter c or C, sometimes indices are used. For example, if the pressure is constant, then the index is p, and if the volume is constant, then v.
Definition variations
Several formulations of the definition of the discussed physical quantity are possible. In addition to the above, a definition is considered acceptable, which states that the specific heat is the ratio of the heat capacity of a substance to its mass. In this case, it is necessary to clearly understand what "heat capacity" is. So, heat capacity is called a physical quantity that shows how much heat must be brought to the body (substance) or removed in order to change the value of 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 has been experimentally found that this value is different for different substances. For example, the specific heat capacity of water is 4.187 kJ/(kg K). The largest value of this physical quantity for hydrogen is 14.300 kJ/(kg K), the smallest for gold is 0.129 kJ/(kg K). If you need a value for a particular substance, then you need to take a reference book and find the corresponding tables, and in them - the values \u200b\u200bof you are interested. However, moderntechnologies make it possible to speed up the search process at times - it is enough on any phone that has the option to enter the World Wide Web, type the question of interest in the search bar, start the search and look for the answer based on the results. In most cases, you need to click on 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 they are looking for heat capacity, 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).
