Physics Heat vs. calorific value, what is heat in physics

Hello to this question you first have to distinguish the relationship between calorific value and heat calorific value , in fuel chemistry, an important indicator that indicates the quality of fuel. The amount of heat emitted per unit mass (or volume) of fuel when it is completely combusted.

Therefore, in order to be able to find the heat emitted by charcoal, you must 1 give the mass 2 give the calorific value1 The main component of charcoal is carbon, and the calorific value is about megajoules.

So the heat obtained from charcoal = between to.

MJ.

2 Calorific value of alcohol: kj kg

So the calories emitted by alcohol = 2000* kj

megajoules. PS 1 megajoules (MJ) = 10 3KJ

q=mq. M represents the mass of the fuel, Q represents the calorific value of the fuel, the calorific value of charcoal is, and the calorific value of alcohol is.

Solution: Q alcohol = MQ = 2000kg

q charcoal = mq = 15kg

The heat released by the complete combustion of charcoal q = m wood q = 15kg *

Heat refers to the energy transferred between the thermal system and the outside world by the temperature difference. To put it simply, a glass of ice water and a cup of hot water, hot water will be hot when you touch it, and the heat transmitted to you is heat. A glass of ice water, you touch it cold, it is absorbing your heat.

Heat repentance is a process quantity, so heat can only be said"Absorption""Release"。I can't say it"Yes""Yes"。And this transfer process is called heat exchange or heat transfer. The unit of heat is joules (j).

What is the nature of heat? This has been a long-debated issue in history, and in the 17th century, some natural philosophers such as Bacon, Boyle, Hooke, and Newton believed that heat is the mechanical motion of particles of objects. However, in the 18th century, with the development of chemistry, thermometry, and calorimetry, the "thermal mass theory" was proposed.

This doctrine holds that heat is an invisible, distracting and weightless substance, called thermal mass, and that hot objects contain more hot mass, and cold objects contain less thermal mass; Heat mass can neither be generated nor destroyed, but can only be transmitted from a hotter object to a colder object, and the conservation of heat mass in the process of heat transfer is the manifestation of the conservation of mass according to the theory of thermal mass, the melting of solids and the evaporation of liquids are regarded as the result of chemical reactions between heat matter and solid and liquid substances.

Calculation formulas and units.

The temperature changes to t through a certain process, and the heat it absorbs (or emits out) q=cm· t q absorb=cm(t t0) q discharge=cm(t0 t) (t0 is the initial temperature;t is the final temperature) where c is the specific heat (capacity) associated with this process The unit of heat is the same as the unit of work and energy The unit of heat in the International System of Units is joules (abbreviated as joule, abbreviated as j) Historically, the unit of heat has been defined as calories (abbreviated as cal), which is currently only used as an auxiliary unit of energy, 1 cal = joule Note: 1 kilocalorie = 1000 cal = 1000 calories = 4184 joules = kilojoules The amount of heat absorbed and released by an area in a certain period of time, The equilibrium relationship maintained by the stored heat. △t=（t1-t0）

The calorific value is not equal to the heat, they are not the same physical quantity.

Heat is the amount of internal energy transferred during heat transfer, which is expressed by q.

The calorific value is the heat released by the complete combustion of 1kg of a certain eggplant fuel, which is expressed by Q.

Calorific value, also known as calorific value or calorific value, is the amount of heat emitted when the fuel is completely combusted. The calorific value reflects the combustion characteristics of fuels, that is, the ability of different fuels to convert chemical energy into internal energy during the combustion process.

Formula for calculating calorific value:

The formula for calculating the heat released by the complete combustion of solid fuels is: q amplification = mq

The formula for calculating the heat released by the complete combustion of gaseous fuels is: q=vq

q denotes heat (j) and q denotes calorific value (

j kg, m is the mass of solid fuel (kg), v is the volume of gaseous fuel (m3).

q=q put m (solid);q=q discharge v (gas).

w=qm=qm=qm

w=qv=qv

w: total work) calorific value is related to pressure).

In food chemistry, the energy of food refers to the amount of heat emitted by 1g of food when it oxidizes in the body.

It is usually determined with a calorimeter and is denoted by j g. For example, the calorific value of sugars is about, the calorific value of fats is about, and the calorific value of proteins is about.

Hello, you have to distinguish between this question first. Caloric value. And.

Relationship of heat.

Caloric value. In fuel chemistry, it is an important indicator of fuel quality. The amount of heat emitted per unit mass (or volume) of fuel when it is completely combusted.

So be able to find it.

When the heat of the charcoal is released.

Must 1 give quality.

The calorific value is given. The main component of charcoal is carbon, and the calorific value is about megajoules.

So find the heat. Charcoal.

Arrive. Between. MJ.

Alcoholic. Caloric value.

kj kg so.

Alcohol calories = 2000*

megajoules. PS 1 megajoules (MJ) = 10 3KJ

Thermal energy is the internal energy of an object. The relationship between the three is as follows:

1. The relationship between internal energy and temperature.

A change in the temperature of an object must cause a change in internal energy.

Because the temperature of the object increases (or decreases), the speed of the irregular motion of the molecules in the object increases (or slows down), and the kinetic energy of the molecules increases (or decreases), so its internal energy must increase (or decrease).

If the temperature of an object does not change, its internal energy may change (an increase or decrease in the internal energy of an object does not necessarily cause a change in temperature).

For example, during the melting process of crystal ice, the heat absorption, the temperature does not change, the molecular kinetic energy does not change, the intermolecular distance decreases, and the molecular potential energy decreases, so the internal energy decreases during the ice melting process. In the process of crystal solidification and melting, the process of liquid boiling, the temperature does not change, and its internal energy changes. There is a temperature difference in the heat transfer process, and when the temperature changes, the internal energy also changes.

2. The relationship between internal energy and heat.

The internal energy of an object changes, and it does not necessarily absorb (or emit heat).

Because there are two ways to change the internal energy of an object, heat transfer can change the internal energy of the object (to absorb or release heat): work can also change the internal energy of the object (not absorbing or releasing heat).

Endothermic or exothermic of an object will inevitably cause a change in internal energy.

In the process of heat transfer, the internal energy of the object is changed, that is, the heat of the high-temperature object is released, and the internal energy is reduced; Objects at low temperatures absorb heat and the internal energy increases. In the process of state of matter, endothermic or exothermic is maintained, and the internal energy increases (or decreases) while the temperature remains unchanged.

3. The relationship between heat and temperature.

Objects absorb heat (or exothermic) and do not necessarily cause temperature changes.

Because only when there is a temperature difference between two objects can heat transfer occur, and internal energy transfer occurs, and the amount of internal energy change is called heat. According to the formula, heat is related to the mass of the substance, the specific heat, and the changing temperature, and has nothing to do with the initial temperature and the final temperature. When the state of matter changes, such as crystal melting or solidification, the temperature does not change during the boiling process of the liquid, and the heat must be absorbed or released.

The temperature of an object changes, not necessarily endothermic or exothermic.

Because there are two ways to change the internal energy of an object: the heat transfer process, which absorbs or discharges heat, the temperature changes, and the internal energy changes; The work is done to change the internal energy of the object, and there is no need to absorb or release heat.

Thermodynamic energy: The sum of the internal energy of the system, also known as internal energy.

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

So it's different.

The relationship between heat and internal energy is like the relationship between work done and mechanical energy. If thermal equilibrium has not yet been reached between the two regions, then heat is transferred from the hot place in the middle to the lower one. Any substance has a certain amount of internal energy, which is related to the disordered movement of the atoms and molecules that make up the substance.

When two substances of different temperatures are in thermal contact, they exchange internal energy until the temperature of the two bodies is the same, that is, thermal equilibrium is reached. Here, the amount of energy transferred is equal to the amount of heat exchanged. Many people confuse heat with internal energy, but in fact, heat refers to the change of internal energy and the work done by the system.

Heat describes the amount of change in internal energy, while internal energy is a state quantity, which is a state function of the system, corresponding to a state point of the system. Knowing the difference between heat and internal energy is the key to understanding the first law of thermodynamics. The heat transferred between objects in the heat transfer process is related to the process (adiabatic, isothermal, isobaric), that is, endothermic or exothermic must be carried out in a certain process When an object is in a certain state, it cannot be said how much heat it contains (heat is the amount of process, equivalent to delta) Note (heat is just a noun in the process of heat transfer, such as it is not correct to say how much heat is in an object, because internal energy is a property of an object, and any object has internal energy, heat:

In heat transfer, the amount of internal energy transferred is called heat. ）