What is hot history?

1. What is thermal history?

At the beginning of the 19th century, the United States launched a westward expansion movement, and groups of adventurers rushed to the west coast of the Pacific.

After the news of the discovery of gold mines in California was confirmed, another wave of immigration was triggered. People put down their work and flocked to San Francisco, trying to realize their dream of gold mining. At the beginning of the 19th century, the United States began its unstoppable westward expansion, pushing its frontier from the Mississippi River to the west coast of the Pacific Ocean.

In 1848, people who marched to California discovered gold mines here, which immediately caused a sensation in the world, quickly formed a gold rush of unprecedented scale, and had a profound impact on the westward movement and the development of the western United States. A huge ***. The gold rush is an important part of the westward expansion movement, like a bright fragment in a magnificent picture.

The product of the "Westward Expansion Movement" The California Gold Rush is closely related to the Westward Expansion Movement in American history. It originated directly from a series of activities of people during the westward expansion movement: First, the gold mine discovered in California in 1848 was located in the Sutter community of New Helvetia, where the Sacramento River and the American River meet , is one of the two largest early American immigrant colonies on the Pacific coast. It was built by American immigrant Sutter in 1848. Secondly, Marshall, the discoverer of gold mines, was one of the American immigrants who conquered the Pacific coast. He was born in New Jersey, a city with developed capitalism, embarked on the journey of "Westward Expansion" in 1844, moved from Missouri to Oregon, and settled in the Sutter community the following year; again, the gold mine was discovered at the Sawfield jointly owned by Marshall and Sutter. When the gold rush broke out, the wood processing here immediately solved the immediate needs of the gold diggers in production and life.

In fact, gold deposits have been discovered many times along the Pacific coast before this. The largest gold discoveries were recorded near Los Angeles in 1841 and in Southern California in 1842.

Neither of these times caused a shocking impact. Although the gold discovery in 1842 also attracted hundreds of gold prospectors, it soon became silent. No more interest. This is because several discoveries before 1848 occurred in Indian areas. The Indian society was still in a very primitive state and they did not understand the economic value of gold.

Furthermore, there were very few immigrants here at that time, the development of the commodity economy was low, and the contact with the outside world was also very limited, so the news of the discovery of gold mines could not spread. However, by 1848, the situation had greatly changed due to the Westward Expansion.

With the continuous entry of immigrants, the continuous development of economic production, and the closer exchanges with the outside world, things such as the discovery of gold mines will no longer "always be local." On January 24, 1848, the gold mine was discovered; on March 15, the "Californian" of San Francisco first published the news; on May 12, the businessman Brenner took the Gold sand samples came to San Francisco from the gold mining area, confirming the discovery of the gold mine; on August 19, a letter describing the discovery was published in the "Herald" in New York, eastern United States, and the news followed Spread almost all over the world.

The gold rush began. The westward expansion movement not only means the expansion of the territory of the United States, but more profoundly allows the commodity economy and capitalist production mode to be widely spread and transplanted in North America.

In the 1840s, the development of Americans in California and their way of thinking, behavioral norms, and interpersonal relationships formed the cultural background for the Gold Rush to take off. The sawmill mentioned above is run according to modern business methods.

According to the contract, Sutter provided the necessary funds for the sawmill, while Marshall, who was responsible for the operation, was compensated with a quarter of the product, and personnel management implemented wage labor. Brenner, who helped spread news of the gold discovery "eventually throughout the world," was an "adventurous businessman, manipulator, and land speculator" who founded a series of businesses in California and had a "headquarters" in the Sutter community. shop".

In March 1848, regular customers of the main store began to offer gold to pay for whiskey and other goods, and Brenner immediately understood the significance of this discovery. Therefore, realizing that there would be unlimited business opportunities, he immediately tried every means to raise supplies to satisfy customers' demand for his goods, and then exchange for a large amount of gold sand.

The activities and relationships of these three people are a microcosm of society at that time, reflecting the connection between the rise of the gold rush and the development and adjustment of the market economy. This connection was created by the westward expansion movement.

The "outbreak" and progress of the California Gold Rush were directly driven by the U.S. government. Looking at the overall situation, the American government attaches great importance to the westward expansion movement and has always fully supported the American cowboys in their journey to the west; specifically, the American government was preparing to formally annex California before and after the rise of the gold rush.

At that time, the United States had just finished fighting the Mexican War with the purpose of realizing "Manifest Destiny", and the idea of ??turning California into another star on the American flag was already a general trend.

*** It is necessary for Americans to enter California in large numbers so that the population in this area can reach the legal limit to apply for California *** in the name of a state.

In June 1848, Mason, the U.S. Governor in California, sent a report to President Polk, saying that the value of the gold mine was "sufficient to pay hundreds of times more than the cost of the Mexican War." ”. On December 5, Polk officially announced the report in a message to Congress, confirming the discovery of gold mines in California.

Many people in the eastern United States who had been dubious suddenly realized this and immediately headed westward, flocking to California. When the gold rush led to a sharp increase in population, which in turn affected the shortage of goods, the U.S. government tried every means to adjust and coordinate the supply of goods, and even sent a delegation to China to ask Chinese merchants to ship goods directly to California.

These all reflect the role and influence of ***. Rushing to the gold discovery site After the news of the discovery of gold deposits in California was confirmed, the United States was boiling and the world was shocked.

San Francisco, just around the corner, was the first to feel the impact of the gold rush. "Nearly all businesses ceased operations, sailors abandoned their ships in San Francisco Bay, and soldiers left their barracks. Servants left their masters and flocked to the places where gold was discovered"; "Farmers mortgaged their fields and houses, pioneers abandoned their cultivated land, workers threw down their tools, civil servants left their desks, and so on. 2. What is thermal analysis and its development history How

The development history of thermal analysis can be traced back to more than two hundred years ago.

In 1780, Higgins in England first used balances in the process of studying lime binders and quicklime. After measuring the weight change caused by heating in the experiment, Japan's Kotaro Honda proposed the concept of "thermal balance" in 1915 and designed the world's first thermal balance. In 1899, Britain's Roberts and Austen used two thermocouples. Connected, the method of differential thermal analysis is used to directly record the change of temperature difference between the sample and the reference material over time; after the Second World War, thermal analysis technology has developed rapidly, and the commercial electronic tube type was commercialized in the late 1940s. The differential thermal analyzer came out, and microquantification was achieved in the 1960s. In 1964, Wattson, O'Nei11 and others proposed the concept of "differential scanning calorimetry", which was then developed into differential scanning calorimetry. Thermal technology has enabled the continuous development and growth of thermal analysis technology. 3. What is "heat"? What is heat?

Since the sixteenth century, there have been different views. The question of the nature of heat has attracted the attention of scientists and researchers. "Heat" is a kind of movement. Bacon concluded from phenomena such as frictional heat generation that "heat is an expansion, restraint and acts on it in its struggle." "The motion on the smaller particles of an object", this view influenced many scientists.

Boyle saw that the iron nail would generate heat after being hammered, and thought that there was a strong movement inside the iron nail. , so he believed that heat is "a strong and chaotic movement of various parts of an object"; Descartes regarded heat as a rotational motion of material particles. Hooke observed sparks with a microscope and believed that heat "is not something else. Rather, it is a very active and extremely violent movement of various parts of an object. "

Newton also pointed out that the particles of objects "are heated by motion." Locke even recognized that "extreme cold is the cessation of the movement of particles that is imperceptible."

Russian scholar Lomonosov presented two papers on physics in the 1840s, the first on the foundations of thermodynamics, entitled "Reflections on the Causes of Heat and Cold" (1746); the second It is about the theory of molecular kinetics, entitled "On the Elasticity of Air" (1748). In these two papers, Lomonosov put forward the following insights: "The sufficient origin of heat lies in motion", that is, heat is. The movement of matter is caused by the tiny particles in the object that are invisible to the naked eye; the particles themselves are spherical, because only in this way can the solid maintain its shape when it heats up; the reason why heat is transferred from high-temperature objects to low-temperature objects , is caused by particles in high-temperature objects transmitting motion to particles in low-temperature objects, and the amount of motion given is equal to the amount of motion received. When one object heats another object, it itself will become colder. This confirms the correctness of the conservation of motion in thermal phenomena; the motion of gas molecules is in a "chaotic" state, which is chaotic and irregular.

"Heat" is a kind of "chaos". But generally speaking, the view that heat is motion lacks sufficient experimental basis, so it cannot be formed into a scientific theory. With the revival of ancient Greek atomic theory, the view that heat is a special material entity has also been spread. .

French scientist and philosopher Gassendi believed that moving atoms are the most primitive and irreducible elements of the world that constitute all things. Similarly, heat and cold are also composed of special "heat" Caused by "atoms" and "cold atoms". They are very detailed, have the shape of a ball, and are very active, so they can penetrate into all objects.

This concept leads people to the "caloric theory" . Boyle also wavered between the theory of motion and the theory of caloric mass.

When investigating the phenomenon that a piece of hot iron placed in a vacuum container can make the wall of the container feel hot, he thought that this seemed to be explained only by the transfer of "heat" itself. Boerhaave believed that the origin of heat is highly plastic and penetrating material particles drilled into the pores of objects. They are weightless, repellent to each other, and permeate the entire universe.

In 1789, Lavoisier also included "heat" and "light" among the twenty-three "elements" in the inorganic world. Blake was an important advocate of caloric theory.

Although he believed that the heat that would eventually occur "would not be chemical but mechanical," he could hardly deny the caloric theory. He felt that there were still many difficulties in the theory that heat is motion.

For example, if heat is the movement of particles inside a substance, then a dense substance is less likely to vibrate due to the strong attraction of its internal particles, so the specific heat should be larger. But why is the specific heat of mercury smaller than What is the specific heat of water? For "latent heat", it is more difficult to explain using the mechanical motion of particles. So Blake declared that he "cannot form the idea of ??this internal vibration" and adopted the view that heat is a special substance.

The theory of caloric mass simply explained most of the thermal phenomena discovered at that time: changes in the temperature of objects are caused by the absorption or release of thermal mass; thermal conduction is the flow of thermal mass, and convection is the object carrying thermal mass. The flow and radiation are the propagation of thermal mass; the thermal expansion of objects is due to the mutual repulsion between thermal mass particles; the "latent heat" when the material state changes is the result of the "quasi-chemical reaction" between the matter-holding particles and thermal mass; friction or collision The heat generation phenomenon is the result of the "latent heat" being squeezed out and the specific heat of the substance becoming smaller; and so on. Due to the material nature of heat, it also obeys the law of conservation of matter, which is the theoretical basis of hybrid calorimetry.

Under the guidance of the caloric theory, the main progress made in thermal research include: Blake discovered specific heat and "latent heat"; Watt theoretically analyzed the main defects of the old steam engine and guided him to improve it. He invented the steam engine; Fourier established the theory of heat conduction based on this physical image; Carnot proposed the theory of consuming heat obtained from a heat source to obtain work from the perspective of heat and mass transfer in the early 19th century. The success of the theory of caloric mass convinced people that it was a correct theory, thus overriding the view that heat is motion and taking a dominant position from the eighteenth century to the beginning of the nineteenth century.

"Heat" is still a kind of movement. However, by the end of the eighteenth century, the caloric theory was seriously challenged. In 1798, physicist Benjamin Thompson, Earl of Rumford, who was born in the United States and later became a British citizen, made a report to the Royal Society, saying that when he was supervising the drilling work of the cannon barrel in Munich, he noticed that the cannon barrel As the temperature rises, the metal chips under drilling become hotter. He raised the question of where the large amount of heat comes from.

He conducted a series of drilling experiments under as insulated conditions as possible, compared the specific heat of metal and debris before and after drilling, and found that drilling and grinding did not change the specific heat of the metal. He also used a very blunt drill bit to drill the gun barrel. After half an hour, the temperature of the gun barrel increased from 60 degrees F to 130 degrees F. The metal debris was only more than 50 grams, which is equivalent to one nine hundred and forty-eighth of the mass of the gun barrel. Can this small amount of debris release such a large amount of "latent heat"? He wrote in his notes: "It seems that in these experiments, the source of heat generated by friction is inexhaustible.

Needless to say, any object or system of objects that is isolated from the outside world can produce unlimited heat. What is provided can never be a specific material entity; in my opinion, it seems difficult to regard the heat excited in these experiments as anything other than 'motion'. ." Six years later, caloricists were still defending Rumford's experiment. 4. What is the nature of heat

Understanding of the nature of heat

One of the earliest natural phenomena that humans come into contact with in life and production is the phenomenon of heat.

What exactly is heat?

There has been a long-standing debate in history

about this.

From prehistoric times until the

18th

beginning of the 18th century,

Although many explorations have been made into the nature of thermal phenomena,

p>

However, because the knowledge we have is not rich enough and the methods are not scientific enough, our understanding of the nature of heat is only some assumptions.

18

Century

First arrival

19

In the middle of the century, the emergence and widespread use of the steam engine promoted The industry developed rapidly. In order to further improve the

efficiency of heat engines, people

conducted in-depth research on the thermal properties of substances,

thus promoting the development of thermal experiments,

Since then, the study of thermal phenomena has embarked on the path of experimental science.

In order to quantitatively explain the experimental results,

Some scholars believe that based on one-sided experimental facts,

Heat is

a substance without mass. The fluid is called caloric;

But the caloric theory cannot explain frictional heat generation,

impact heat generation and other phenomena.

Other scholars

believe that heat is not a fluid, but a manifestation of material movement.

1842

German doctor

J

.

R

.Meier's paper proposed the theory of energy conservation. He believed that heat is a kind of energy that can be converted into mechanical energy. Later

J

.

P

. Before and after Joule

It took decades to do Conducted many experiments,

measured the equivalent of heat work,

obtained completely consistent results,

thereby providing insights into energy conservation

and transformation The law laid a solid foundation.

1

, the theory of caloric mass and the development of calorimetry

Ancient atomists believed that heat is a material; modern Gassendi (

p>

Gassendi

Pierre

,

1592

~

1655

) also clearly proposed the concepts of "hot atoms" and "cold atoms", believing that objects heat up because of the action of "hot atoms". Gassan

Although Di's theory was only speculative,

it was taken seriously by later physicists,

and thus the theory of caloric mass was developed. explain.

Caloric mass

According to the theory of heat, heat is a self-repelling, weightless fluid called caloric mass. It is immortal and can penetrate into all

objects. Whether an object is "hot" or "cold"

is determined by the amount of thermal mass it contains. The hotter object contains more

thermal mass.

When two objects with different hot and cold temperatures come into contact,

the thermal mass is transferred from the hotter object Drain into the cooler object

until both are at the same temperature

.

The theory of caloric mass can indeed explain most of the thermal phenomena encountered at that time:

The change in the temperature of an object can be regarded as the absorption or release of thermal mass

Caused by,

Heat conduction is the flow of thermal mass,

Objects expand when heated because thermal mass particles repel each other,

Latent heat is matter

< p> The result of chemical reaction between particles and caloric particles.

Since caloric is a substance;

The caloric mass reduced by one object,

is exactly

equal to the mass reduced by another object. Increased heat mass;

Therefore, heat mass is conserved during the transfer process;

That is, it follows the law of conservation of matter.

Caloric quality

These advantages won the approval of most scholars at that time.

In 1738

the French Academy of Sciences offered a reward for

papers on the nature of heat.

The three winners were all caloric theorists. advocates.

It can be seen that the caloric theory was accepted by many people at that time.

Because this theory

can explain some physical phenomena and experimental results more intuitively, it has been widely recognized.

Thermal science begins with the quantitative study of thermal phenomena.

The first sign of quantitative research is to measure the temperature of an object.

As early as

in the last century,

Galileo had already built the first thermometer.

Later, the Italian Zimanto The members of the society continue to study

the thermometer.

The basic basis for temperature measurement is the thermal expansion and contraction of matter.

Secondly, there must be an agreed scale system.

Galileo's thermometer

The thermometer uses the expansion of air when heated and the contraction when cooled,

but does not have a fixed scale.

The Zimanto Society used the coldest and

hottest times of the year as two fixed points,

and developed a rough measurement system .

They discovered that

the melting point of ice is a constant,

which inspired later people to use this as a fixed point. Huygens in 1665

proposed using the temperature of melting ice or boiling water as a reference point for measuring

temperature.