Thermodynamics

# What is Difference Between Heat and Temperature?

Heat and temperature are two different quantities. The basic difference between heat and temperature is that Heat is the form of energy that transfers from hot body to cold body. Its unit is joule. While the temperature is the degree of hotness and coldness of the body. Its SI unit is Kelvin.

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## heat and temperature difference

 Heat Temperature Heat is a form of energy that can transfer from hot body to cold body. Temperature is the degree of hotness and coldness of a body. Heat is the total kinetic energy and potential energy obtained by molecules in an object. Temperature is the average K.E of molecules in a substance. Heat flows from hot body to cold body. It rises when heated and falls down when an object is cooled down. It has a working ability. It does not have the working ability. Its SI unit is “Joule”. Its SI unit is “Kelvin”. It is measured by the calorimeter. It is measured by the thermometer. It is represented by “Q”. It is represented by “T”.

## What is the heat?

“Heat is a form of energy that flows between a system and its environment by virtue of a temperature difference between them.”Heat is, therefore, called as the energy in transient. Once the heat enters a body, it becomes its internal energy and no longer exists as heat energy.

It is a common observation that if you place a hot object (say a cup of tea) or a cold object (say a glass of ice water) in an environment at ordinary room temperature, the object will tend toward thermal equilibrium with its environment. That is, the hot cup of tea gets colder and the ice water gets warmer; the temperature of each approaches the temperature of the room.

It seems clear that such approaches to thermal equilibrium must involve some sort of exchange of energy between the system and its environment.

Heat is an important form of energy. It is necessary for our survival. We need it to cook our food and to maintain our body temperature. Heat is also needed in various industrial processes. How to protect ourselves from high as well as low temperature, needs knowledge of how heat travels.

Heat is similar to work in that both represent a means for the transfer of energy. Neither heat nor work is an intrinsic property of energy. Neither heat nor work is an intrinsic property of a system; that is, we cannot say that a system “contains” a certain amount of heat or work. Instead, we say that it can transfer a certain amount of energy as heat or work under certain specified conditions.

some of the confusion about the precise meaning of heat results from the popular usage of the term. Often heat is used when what is really meant is temperature or perhaps internal energy. When we hear about the heat in relation to weather, or when cooking instructions indicate”heat at 300 degrees,” it is the temperature that is being discussed. On the other hand, we we also hear references to the “heat generated ” by the brake linings of an automobile or by briskly rubbing the palms of your hands together. In this case, as we shall see, it is usually internal energy that is meant. A  clue to the proper usage comes from the definition of heat: When you rub your hands together, they do work on one another, thereby increasing their internal energy and raising their temperature. This excess energy can then be transferred to the environment as heat because the hands are at a higher temperature than the environment.

### Unit of heat:

Because heat is a form of energy, its units are those of energy, namely, the joule (J) in the SI system. Before it was recognized that heat is a form of energy, other units were assigned to it. In some cases, these units, specifically the calorie(cal) and the British thermal unit (Btu) , are still in use today. They are related to the joule according to:

1 cal =4.186 J

1 Btu=1055 J.

The “calorie” in common use as a measure of nutrition (Cal) is, in reality, a kilocalorie; that is,

1 Cal = 1000 cal = 4186 J.

The Btu is still commonly found as a measure of the ability of an air conditioner to transfer energy (as heat) from a room to the outside environment. A typical room air conditioner rated at 10,000 Btu/h can, therefore, remove about 10 7 J from a room every hour and transfer it to the outside environment.

The Mechanical Equivalent of Heat:

In the past, when the calorie was independently defined as a unit of heat, it was necessary to determine an empirical relationship between the calorie and the joule. This was first done by James Joule in 1950 in an experiment to determine the mechanical equivalent of heat. The result of Joule’s experiment, and others that followed provided for nearly 100 years a conversion between the Joule and the Calorie. Today, following the adoption in 1948 of the joule as the SI unit of heat and work, in J, and so this conversion factor has lost the importance it had in Joule’s time. Nevertheless .joule’s work is still noteworthy for the skill and ingenuity of his experiments,for its precision (joule’s results differ by only 1 % from the SI defined relationship between the joule and the calorie),and for the direction it provided in showing that heat, like work, could property be regarded as a means of transferring energy.

### What are the main sources of heat energy?

• The sun is the biggest source of heat. Sun’s heat reaches the Earth in the form of radiations. Solar radiations keep the Earth’s environment warm at a suitable temperature for the survival of life.
• We keep our body warm and alive by the heat produced from the food during its metabolism in the body cells.
• Heat is also produced by burning of Fossil fuels(wood, coal, oil, and gas, etc). We cook food and warm our rooms by the heat produced by the burning of wood and natural gas, etc. The heat produced by the burning coal and oil etc. is used to produce electricity in thermal power stations.
• Electricity is also used to produce heat.
• Heat is obtained from nuclear reactions like Fission and Fusion.
• Biomass gas is also a source of heat.

### Differentiate between thermal expansion and contraction?

All kinds of material objects are made up of tiny particles such as atoms and molecules. When an object is heated, the object expands. This expansion of material objects on heating is called thermal expansion. On the other hand, when an object is cooled, the object contracts. This contraction of material objects is called thermal contraction.

## What is temperature in physics?

“The temperature of a body is the degree of hotness or coldness of the body.” or “Average kinetic energy of atoms or molecules.”When we touch a body, we feel it hot or cold. The temperature of a body tells us how hot or cold a body is.

When two systems are in thermal equilibrium, we say that they have the same temperature. Conversely, the temperature is that property of a system that equals that of another system when the two systems are in thermal equilibrium. For example, suppose the systems are two gasses that initially have different temperatures, pressure, and volumes. After we place them into contact and wait a sufficiently long time for them to reach thermal equilibrium, their pressures will in general not be equal, nor will their volumes; their temperatures, however, will always be equal in thermal equilibrium. It is only through this argument based on thermal equilibrium that the notion of temperature can be introduced into thermodynamics.

A candle flame is hot and is said to be at high temperature. Ice, on the other hand, is cold and is said to be at low temperature. Our sense of touch is a simple way to know how much hot or cold a body is. However, this temperature sens is somewhat approximation and unreliable. Moreover, it is not, always safe to touch a hot body. What we need is a reliable and practicable method to determined the relative hotness coldness of bodies.

To understand the concept of temperature, it is useful to understand the terms, thermal contact, and thermal equilibrium. To store ice in summer, people wrap it with a cloth or keep it in a wooden box or in a thermos flask. In this way, they avoid the thermal contact of ice with its hot surrounding otherwise ice will soon melt away. Similarly, when you place a cup of hot tea or water in a room it cools down gradually. Does it continue cooling? It stops cooling as it reaches the room temperature. Thus, temperature determines the direction of flow of heat. Heat flows from a hot body to a cold body until thermal equilibrium is reached.

What happens when we touch a hot body? Take two bodies having different temperatures. Bring them in contact with each other. The temperature of the hot body falls. It losses energy. This energy enters the cold body at a lower temperature. The cold body gains energy and its temperature rises. The transfer of energy continues till both the bodies have the same temperature. The form of energy that is transferred from the hot body to a cold body is called heat. Thus “Heat is the energy that is transferred from one body to the other in thermal contact with each other as a result of of the difference of temperature between them.”

Heat is, therefore, called as the energy in transit. Once heat enters a body, it becomes its internal energy and no longer exists at heat energy.

### What is the internal energy of a body?

Internal energy is the sum of kinetic energy and potential energy associated with the atoms, molecules, and particles of a body.

The internal energy of a body depends on many factors such as the mass of the body, kinetic, potential energies of molecules etc. The kinetic energy of an atom or molecule is due to its motion which depends upon the temperature. The potential energy of atoms or molecules is the stored energy due to intermolecular forces.

The device that is used to measure the temperature of a body is called Thermometer.

Related topics :

What are the different temperature scales?

Difference between heat and temperature

Types of transducers

Heat transfer by conduction

Heat transfer by convection examples

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1. Antaransanyal says:

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