What is the difference between heat and internal energy? What s the connection?

I also have a headache for thermal science, so I will analyze it for you according to my understanding of learning, I hope it will be useful to you!

Heat and internal energy are two concepts that are distinctly different: heat refers to the amount of heat energy exchanged between the thermal system and the outside world through the interface, and it is the amount of process related to the thermal process, and the heat exchanged with the outside world through different processes is different. Internal energy refers to the sum of the energy of a large number of microscopic particles in the thermodynamic system, which is the state quantity that is not related to the thermodynamic process but only to the thermal state in which the thermodynamic system is located.

In short, heat is the amount of heat energy transported, and internal energy is the storage of heat energy. The connection between the two can be expressed by the first law of thermodynamics, which can be concluded from the first law of thermodynamics (conservation of energy): the transport of heat may cause changes in internal energy in addition to work or work expended.

Difference Between Temperature, Internal Energy and Heat:

1. The concept is different.

Temperature: Temperature is a physical quantity that indicates how hot or cold an object is, and microscopically it is the intensity of the thermal motion of the molecules of an object.

Heat: Heat refers to the thermal interaction between the system and the outside world when the change of the state of the system is due to the destruction of the thermal equilibrium conditions, that is, when there is a temperature difference between the system and the outside world.

Internal energy: Generally refers to all the energy in an object.

2. The scope of coverage is different.

Temperature: From the point of view of molecular kinematics, temperature is a sign of the average kinetic energy of the molecular motion of an object.

Internal energy: including the energy of molecular thermal motion, the potential energy of interaction between molecules, the energy of internal motion of molecules and atoms, and the energy of electric and magnetic fields.

Thermal energy: Essence is the sum of the kinetic energy of the irregular movement of all the molecules inside the object.

3. The unit of representation is different.

Temperature: Fahrenheit (°F), Celsius (°C) and international utility temperature scales.

Calories: The unit of heat is "kcal".

Internal energy: The unit is "joules".

The connection between temperature, internal energy and heat:

1. Temperature and internal energy.

The higher the temperature, the faster the molecules in the object move irregularly, and the greater the average kinetic energy of the molecules, so the more internal energy of the object.

2. Temperature and heat.

Temperature reflects how violently the molecules move irregularly. The more intense the molecular motion, the higher the temperature of the object. Heat is the amount of internal energy transferred during heat transfer. An object with a high temperature emits heat and the internal energy decreases, while an object with a low temperature absorbs heat and the internal energy increases.

3. Quantity and internal energy.

Heat reflects the amount of internal energy transferred during heat transfer. The amount of heat emitted by the object decreases the amount of internal energy; The amount of heat absorbed by the object increases the amount of internal energy.

Extended information: 1. Work can change the internal energy of an object. (e.g. drilling wood for fire).

When an external force does positive work on an object, the internal energy of the object increases, and vice versa.

2. Heat transfer can change the internal energy of an object. (e.g., placing ice cubes to cool down objects).

There are three forms of heat transfer: heat conduction, heat convection (generally found in gases and liquids), and heat radiation, which is conditional on a temperature difference between objects.

Work done and heat transfer are equivalent in the effect of changing the internal energy. Work is done to convert other forms of energy, such as mechanical energy, into internal energy; Heat transfer causes the internal energy to be transferred between objects.

The difference between internal energy and thermal energy is as follows:

1. The influencing factors are different. The magnitude of heat energy changes monotonically with temperature; In general, there is no definite genus relationship between internal energy and temperature concentration.

2. The concepts of the two are different. Since internal energy refers to all the energy in the object, its extension is obviously wider than that of thermal energy, from the perspective of the relationship between concepts, internal energy and thermal energy are also a subordinate relationship, in which internal energy is a genus concept, and thermal energy is a kind of concept.

3. The scope of coverage is different. Internal energy includes the thermal motion of molecules.

Energy, potential energy of interaction between molecules, molecules and atoms.

the energy of internal motion, as well as electric and magnetic field energy, etc.; The essence of thermal energy is the sum of the kinetic energy of all the molecules moving irregularly inside the object.

Heat energy is the energy of life. All activities such as daily work activities, sports, classes and studies, as well as the maintenance of normal body temperature.

and various physiological activities, all of which consume energy. It's like a steam engine.

Just as coal is burned, internal combustion engines need gasoline, and electric motors need electricity.

Microscopically, internal energy is the statistical average of the sum of energies moving randomly by molecules.

The energy of the random motion of a molecule includes the kinetic energy of the molecule, the potential energy of the interaction between the molecules, and the energy of the internal motion of the molecule. The internal energy of an object does not include the kinetic energy of the entire motion of the object and its presence in the gravitational field.

potential energy.

Internal energy: refers to the total energy contained in the interior of the object, which includes not only the kinetic energy of the irregular thermal motion of molecules, the potential energy of the interaction between molecules, but also the energy in the molecule atom, the energy in the nucleus, etc. In thermals, the latter two items do not change due to the fact that in thermal motion.

Therefore, the internal energy generally refers to the first two items. Since the kinetic energy of a molecule is related to temperature, and the potential energy of the interaction between molecules is related to the distance between molecules, the internal energy of an object is related to temperature, the interaction between molecules, and the number of molecules.

Temperature: A physical quantity that indicates how hot or cold an object is. From the point of view of molecular kinetic theory, temperature is a sign of the average kinetic energy of a molecule. The higher the temperature, the greater the kinetic energy of the molecule.

Heat: Refers to the amount of change in internal energy during heat transfer. It is a process quantity, which is a measure of the change in internal energy in heat transfer.

1.The relationship between temperature and internal energy.

The temperature microscopically reflects the intensity of the irregular movement of a large number of molecules inside the object, and it is related to the kinetic energy of the molecules of the object, and the more intense the thermal motion of the molecules of the object, the higher its temperature. For the same object, the temperature increases, the irregular motion of the molecules accelerates, and its internal energy increases; Conversely, when the temperature decreases, the internal energy decreases. But there are two things to note here:

One is that when the temperature of the object is unchanged, the internal energy may not change, but it may also decrease or increase, for example, the water of 0 solidifies into 0 ice (or the ice of 0 melts into 0 water), although the temperature does not change, but the intensity of molecular movement changes, so the internal energy also changes. Second, the internal energy of an object is not only related to its temperature, but also related to the number of molecules, the type of substance and the distance between molecules, so it should be noted that the internal energy of an object with high temperature is not necessarily more.

2.The relationship between heat and internal energy.

The essence of heat is the process of transfer of internal energy. For example, heat transfer occurs between two objects, and a high-temperature object emits 50 J of heat, which means that its internal energy is reduced by 50 J; Similarly, if a low-temperature object absorbs 50J of heat, the internal energy increases by 50J, which is actually 50J of internal energy transferred from a high-temperature object to a low-temperature object.

The object absorbs heat, the molecules move violently, and the internal energy increases, but the increase in internal energy can be achieved not only by endothermy but also by doing work on the object. When we are not clear about the process of internal energy change, we are not sure which way it is achieved.

It is also important to note that heat is a process quantity, while internal energy is a state quantity, so it cannot be said that an object contains heat.

Internal energy: The sum of the kinetic and potential energy of all the molecules in the object is called the internal energy.

Heat: Heat is a process quantity (energy) that cannot be said to be possessed or contained, but can only be said to be absorbed or released.

Internal energy is the sum of the energy of all forms of motion of all microscopic particles in an object or a system composed of several objects (referred to as a system).

Heat refers to the energy transferred during the energy conversion due to the presence of temperature differences.

The relationship between heat and internal energy is like the relationship between work done and mechanical energy. Heat is a physical quantity that measures the change in internal energy.