Heat : Introduction And Classification

Heat is one of the essential forms of energy for the survival of life on earth. It plays a significant role in our lives. We use heat energy for cooking, ironing, transportation, recreation etc. This form of energy also plays a vital role in nature. The occurrence of the wind, rain, change of seasons etc. is all dependent on the gradient created due to uneven heating of different regions.

What is Heat?

With the increase in temperature of a body, the vibrations of molecules or atoms increase. These vibrations are then transferred from one part of the body to another. The measure of energy with which the molecules vibrate in a system is termed as heat stored in that object.

It flows from a body at a higher temperature to a body at a lower temperature. This is because the molecules vibrating faster transfer their energy to the molecules vibrating slower. The vibrational energy is also termed as its heat content. The heat content in the body makes it hot or cold. Greater the heat content, hotter will be the body.

Heat as a form of energy can be converted to other forms of energy. For example, in motorized vehicles, heat is converted to mechanical energy. In electric bulbs, it is converted to light energy. In thermal power plants, it is finally converted to electrical energy.

Heat - Cold

Let us take three beakers, first with cold water, the second with hot and the third with water at normal temperature. If we dip our finger in beaker 1 and then in beaker 3, we will observe that water in beaker 3 is hot as compared to that in beaker 1. Whereas, if we dip our fingers in beaker 2 and then in beaker 3, we will observe that the water in beaker 3 is colder as compared to that in beaker 2. This shows that we cannot rely on our sense of touch to judge the hotness or coldness of something and that’s why the degree of hotness or coldness of any object is measured in terms of temperature.

Classification of Heat 

Heat can be classified as follows:

  • Hot
  • Cold

Hot

Objects with high heat content are defined as hot (Hotness or coolness of an object is a relative term is always measured with respect to a reference object).

Examples of hot objects around us include the sun, fire, hot pans, air from a hairdryer, lava from volcanic eruptions, etc.

Cold

Objects with lower heat content are defined as cold objects. Hotness or coolness of an object is a relative term is always measured with respect to a reference object.

Examples of cold objects around us include ice, air from an air conditioner, cold drinks metal vessels kept in open in cold winter days etc.

Sources of Heat

There are many sources of heat but following are the main sources of heat:

  • Sun
  • Chemical
  • Electrical
  • Nuclear

Difference Between Heat and Temperature

Following is the table explaining heat vs temperature:

Parameter Heat  Temperature 
Definition  Heat is defined as the total energy of an object that has molecular motion inside it Temperature is defined as the measure of the thermal energy of an object
SI Unit Joule  Kelvin 
Symbol

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