Section 5 Heat

It feels hot in the summer and cold in the winter, and usually we take our own hot and cold sensations as our judgment of the environment. But this judgment is not accurate, and even the opposite judgment will occur. For example, the same well water, in the hot summer season, this water is really refreshing, and in winter, a pair of frozen hands feel really warm like spring. Therefore, the concept of temperature needs to be introduced to accurately measure hot and cold. The environment we live in is the most accessible environment to water, which is defined by the freezing point of water as 0 degrees Celsius and the boiling point as 100 degrees Celsius (at sea level). This is how the Swede Theseus divided the temperature. The Dutchman Valentheitt developed another method of classification, setting the freezing temperature of a certain concentration of salt water at 0 degrees, the freezing temperature of pure water at 32 degrees, and the temperature of boiling water at 212 degrees. Commonly we call this Celsius or Fahrenheit. China uses Celsius temperature division, and the following description uses Celsius for all temperatures.

After the temperature is defined, the hot and cold effect of any object in the universe is expressed by its temperature. In principle, there is no upper limit to the temperature, which can be arbitrarily high (in fact, the speed of light gives the upper limit of the corresponding temperature), but there is a lower limit, the lowest to minus 27315 degrees, which is recorded as -27315C. This one was a surprise. The internal temperature of the sun is millions of degrees, the surface of some stars is more than 10,000 degrees, and the surface temperature of the sun is 5500C. The hottest places on the Earth's surface are volcanic craters, which can reach more than 1000C, and in Antarctica, the coldest places can reach -89C. The temperature at which life on most Earth can survive is roughly from 0C to 50C. A few can live in extreme environments. Bacteria in the tundra can survive at -150C, and bacteria near hydrothermal vents can survive at 400C. Most mammals have a body temperature close to ours, maintaining a temperature of around 37C. Our body temperature is basically constant, and if it is too high or too low, it can be life-threatening.

We feel different about the temperature and the heat is different, but it is not the temperature that determines the difference. Boil water on the stove, boiling a small pot of water and a large pot of water for a different time. The body is exposed to the air of 0C, and the human body can hold on for a long time, but the human body is soaked in 0C water and will soon die. The difference is due to heat.

First, heat can be transferred. When boiling water, the temperature of both gas and electric stove wire is above 800C, and the temperature of boiling water is only 100C, so the heat is transferred from the gas pot to the water. The temperature is 0C, and our body temperature is 37C, so the heat is transferred from the body to the air. The change in heat brings about a change in temperature. We define calories, units with calories. Just like defining the length in meters. 1 calorie is the amount of heat required for 1 gram of water to rise by 1 degree Celsius. The large pot of water has more water than the small pot and requires more heat to raise one degree, while the heat provided by the stove is fixed, so it burns slowly. The temperature rises or falls because of the entry or loss of heat. Whereas, the entry or loss of heat is due to the difference in temperature between the two sides where the heat enters and exits.

Secondly, the heat requirements of different substances are different when the temperature changes. Of all the substances, isothermal water requires the most heat for the same weight of the substance. In other words, with the same weight and the same amount of cooling, the water cools down and releases the most heat. Heating 1 gram of air to raise the temperature by 1 degree requires only one-sixth the heat of water, and 1 gram of air is almost 1,000 times the volume of 1 gram of water! When the body transfers heat to the air, the air on the surface of the body is quickly heated, and the skin loses heat and the temperature drops. When the temperature is the same, there is no longer heat transfer. The air temperature farther away from the skin is lower than the air temperature on the surface of the skin, so the heat continues to transfer away from the skin. The temperature of the air on the surface of the skin decreases, which in turn leads the skin to continue to dissipate heat to the air. It's similar on the inside of the body. From the muscles to the skin, the temperature gradually drops. In this way, from the muscles to the air, a continuous state of continuous temperature drop is formed. For example: 37C for muscle, 35C for the inner layer of fat, 30C for the outer layer, 20C for the skin, 15C for the surface air of the skin... Distant air 0c. At this time, the body is constantly dissipating heat outward, maintaining a stable temperature distribution. The human body can survive if the amount of heat produced by the body is greater than or equal to the amount of heat needed to maintain the above temperature distribution. In this case, a gust of wind destroys the temperature distribution formed by the air on the surface of the body, directly allowing the 0C air to reach the surface of the body, and the human body immediately dissipates more heat. At this time, the condition of the body is equivalent to the temperature distribution established by the human body when the temperature of the air is -20C. In winter, the temperature remains the same, and the body feels completely different on windy and non-windy days. The animal's dense outer fur keeps a large amount of air unaffected by wind, thus establishing a static temperature distribution that minimizes the effects of harsh climates. The same principle applies to human beings using animal fur to make clothes, and to fill the middle of the clothes with down. When people are in water, such as in the ice sea of the Arctic, the sea temperature is a little lower than 0C. The skin is almost 1,000 times heavier than the same volume of air, and 4,000 times more heat is needed to heat up to one degree. To maintain the same temperature distribution, the heat emitted by the human body is far from enough. So the body temperature will drop dramatically. In fact, you can survive for 15 minutes by curling up your whole body and trying your best to keep your abdomen and armpits warm. Otherwise, you will die in 5 minutes. Also near the North Pole, the first snow of the summer fell on the bare skin of the Inuit as they melted and they slept peacefully for the New Year. Ponder:

140,000 years ago, prehistoric humans were able to enter the cold of Europe and subsequently conquer Siberia with the invention of heavy dà, the technique of double-curled sewing, so that fur clothes did not leak from the wind. You also need to wear similar clothes in the summer in the desert, why?

2 The elephant has no hair, and its close relative, the mammoth (extinct most than 4,000 years ago), also known as the mammoth, is covered in hair. The rhinoceros is also hairless, but its close relative, the woolly rhinoceros, is also hairy (extinct as late as 10,000 years ago). What environment should these extinct close relatives estimate live?

3. There are winter swimmers, who swim on the ice in winter. How long can you expect to swim? Why do you get red when you get out of the water?

4. Swimming starts in early summer, and the water temperature is still low. When I first entered the water, my body felt very cold, and after a while, I got used to it. What does this mean? Finally, you can measure the body surface temperature and water temperature, and let those who have not swam feel it with their fingers.

5. The heat of the human body comes from the energy storage in the body. Shivers occur when the body's calorie supply is insufficient, and the fact is that the muscles are releasing heat. Many times drinking high alcohol to keep out the cold is actually drinking to quench your thirst. At this time, eating something high in calories is a serious thing to do. Why?

6 Russian aunts, basically synonymous with fat people. Southerners, such as those in the Lingnan region, look thin. Why? Polar bears, seals, and walruses all live in icy water, but what is the difference between their bodies and human bodies?

7 Large whales are often active at the poles, and humans have been hunting whales in large numbers since the 19th century. It was the era of the Industrial Revolution, and before the oil industry began, whales were natural warehouses that supplied lubricants, candles, why?

8Those who like to sunbathe and bask in the sun in the ice and snow. To be sure, the weather was windless that day. If it's windy, how many minutes can you last?

9. If the muscle temperature is lower than normal, some functions will be lost. If the temperature is not enough, it is a freezing effect. The parts of people that are prone to freezing include hands, feet, ears, and nose. Why?

10. The human body inhales air and heats or dissipates heat. The flat nose is easy to dissipate heat. The tall and narrow nose heats up quickly. Looking at the nose, you know that the ancestors lived there for a long time.

11 Birds that live near the water, have thick downy on their abdomen, and a large amount of air is fixed in the middle. When in water, this air acts as a barrier to prevent water from coming into direct contact with the skin, providing a good thermal insulator. When we use down jackets, we fill the inner layer of the garment with these fluffs to form an insulating layer. Similarly, cotton has a similar effect.

Wear a cotton jacket in the morning, wear yarn in the afternoon, and eat watermelon around the stove. This is the scene in a day in Xinjiang. Sauna summer, before dawn, it is hot, the sun shows its head, and the steamer begins to steam. It's a marathon weight loss process, but in addition to being uncomfortable, it's still so fat. It lasted until the early hours of the morning, and finally I was sleepy. This is the scenario in the Yangtze River basin.

The situation in Xinjiang shows that the temperature difference between day and night is very large. This is also the reason why Xinjiang melons and fruits are sweet. During the day, the sunlight is strong, the temperature is high, the plant photosynthesizes, and synthesizes a large amount of sugar. The temperature is low at night and the consumption of plants is low. The combined result is a high sugar accumulation. Why is there a large temperature difference between day and night? The sun came out, the sky was clear and cloudless, and a lot of heat was transferred to the ground. The ground has a high proportion of sand, and for the same amount of heat, sand rises four times as hot as water. A small amount of heat can raise the temperature of the sand very high. The temperature of the ground rises, and the air is heated by the ground again, so the yarn is worn at noon. But in a cool place or indoors, the temperature is not high. Another important factor is that the water vapor content in the air is low, and people's sweat is easily volatilized, so it looks dry. It has a similar effect in Kunming, a plateau, but the Cheng dù is lower. The sun has set, losing the heat replenishment of the sun. The heat on the ground and in the air is still radiating into space. Although the temperature is very high, the actual heat stored is less, and there are no factors that hinder heat dissipation, and it is quickly dissipated, and the temperature is reduced to the point where the heat dissipation is balanced. So it's cold at night.

The situation in the Yangtze River basin shows that the temperature difference between day and night is small. Saunas are caused by the fact that the water vapor content in the air is reaching its limit. In this way, it is difficult for the human body to volatilize sweat and is attached to the surface of the body. It felt sticky and uncomfortable. In summer, the Yangtze River basin is covered by a subtropical high (see page 16), with high temperatures, weak air convection, and few but little winds. In particular, there is a lack of vegetation in the city to assist in cooling, which leads to sweltering heat all day long. Although the temperature is not as high as in Xinjiang, the body's own cooling measures are ineffective, and it is useless to hide anywhere. Air conditioning can make the temperature of a confined space suitable, and the consequence is to worsen the entire external environment, and the deterioration effect is greater than the appropriate effect of the confined space. As for how much it is, it depends on the efficiency of the air conditioner. So there is also a part of the sauna weather that people contribute. The surface soil is the main soil, the water content is large, the heat stored is large, and the water vapor and clouds in the air are all factors that hinder the heat dissipation. So the heat dissipation effect is not good at night. In other parts of the planet at the same latitude, a large number of them are deserts. It's all caused by the subtropical high pressure and people, and the Sahara Desert is still a grassland in prehistory. Of course, the climate is the main factor, and the environment is too fragile, and people just push it a little, and the environment will never recover. The same situation is also observed in eastern Xinjiang and western Gansu and Inner Mongolia.

In the tropics, the temperature is always very high, and there are no four seasons, only the rainy and dry seasons. The rainy and dry seasons alternately depend on the direction of the monsoon. And warm and moist air currents can only come from the ocean. In Xishuangbanna, the dry season is from November to April, and the rainy season is from April to November. Then the corresponding monsoon situation is from November to April, when the northeast wind blows, so it is the dry season. From April to November, the southwest wind blows, and the wind comes from the Indian Ocean, so it is the rainy season. The Pacific Ocean can reach as far as Xining, Qinghai, and the Atlantic Ocean as far as the Ili River Valley in Xinjiang. Qinghai and most of Xinjiang, central and western Gansu, central and western Inner Mongolia, no ocean air currents arrived. Without the Himalayas and the Tibetan Plateau, the Indian Ocean is estimated to be reachable. The air currents frequented here are mainly Siberian cold currents, so there is little rainfall. The landform is dominated by grasslands and deserts, and the water mainly comes from the melting of glaciers. Oases and trade staging stations were formed where inland rivers flowed, and occasionally agricultural cultivation was carried out. In recent decades, the rapid warming of the global climate has led to insufficient accumulation of glaciers, which have receded year by year, and the water supply in areas that depend on glacial meltwater has become increasingly difficult.

(This chapter is not finished, please turn the page) Think:

1 China's cultivated land area is currently concentrated in South China, the Yangtze River Basin, North China and Northeast China. Cultivated land has a high demand for water supply. And the grassland requirements are very low. Historically, the Great Wall was the main barrier against attacks by steppe nomadic tribes. Is it a coincidence that the rainfall requirement for agriculture is 400 mm, and China's 400 mm rainfall line is more consistent with the route of the Great Wall?

2. What are the requirements for areas with a small temperature difference between day and night? Which are the main factors?

3. The water vapor content in the air is described by humidity, and the humidity reaches 100%, which means that the water vapor in the air has reached the maximum amount and can not be increased. Humidity and temperature are closely related, and the higher the temperature, the more water vapor is allowed to store zài in the air. Humidity generally refers to the proportional relationship between the amount of water vapor in the air and the maximum zài value at the current temperature, which is called relative humidity (absolute humidity refers to the proportional relationship between the amount of water vapor and the amount of air). Sauna weather, humidity is close to 100%, on the water pipes, you can see a large amount of condensation droplets, why? Also the driest place on Earth is in Antarctica, why? Why can't the Atacama Desert compare?

4 Early civilizations, surrounded by large rivers. Egypt has the Nile, Sumerer has the Euphrates and Tigris, India has the Ganges, and China has the Yellow River. Why? Greece did not have large rivers, but its civilization spread to the Mediterranean and Black Sea regions. And those civilizations that have great rivers, but they have not spread?

5. Rice cultivation, China's Yangtze River basin is considered to be the earliest in the world. Later, it was found that it was also cultivated in the Indochina Peninsula at the same time. Wherever it originated, it is known from the name of this crop that the possibility of large-scale promotion is lacking. Of the five grains (or), the four common grains have a smaller need for water. But rice is produced in many arid areas, such as Aksu in Xinjiang, Zhangye in Gansu, and Taiyuan in Shanxi.

6 In China's history, there have been several large-scale cooling and drought, which led to great changes in the living range of zhì species. 8,000 years ago, the Tibetan Plateau became cold, and agricultural tribes in the upper reaches of the Yangtze River and the Yellow River moved. 5,000 years ago, elephants were distributed from Gansu to Beijing and then migrated south. In the middle of spring and autumn, the Yellow River basin became cold and dry, and rhinos roamed here. At the end of the Northern Song Dynasty, all the bamboos in Henan froze to death, and it was difficult to have any more bamboos in the north. At the end of the Ming Dynasty, the entire north was cold and arid, and the agricultural harvest failed or failed. At other times, there may be small- to medium-scale climate changes. The climatic factors behind the large-scale invasion of nomadic tribes are also a major contributor. The nomadic tribes from the Black Sea to the Sea of Okhotsk (Tang: Shaohai) could experience the changes in the climate when historical records of settled civilizations appeared. Can you find periods when the climate is warmer and wetter?

7 Venus has a dense atmosphere, mainly carbon dioxide, a gas that favors heat accumulation and dissipation, so the surface temperature can reach 400C. As the Earth's climate warms, the amount of carbon dioxide in the air increases. The increase in carbon dioxide levels also leads to climate warming. So which is the cause? Is that a fruit? Perhaps this simplistic judgment is not appropriate.

8 space shuttles, in space, the temperature in places where the sun is exposed is more than 100C, and in shaded places is -100C. Although the temperature difference between day and night in Xinjiang is large, it is far from being comparable to this. Although the earth's atmosphere is not dense enough, I feel that it is valuable now. If it is dense to Venus, the temperature difference between day and night will basically disappear, and there will be no way to eat fruits and grains. In short, the planet is the best.

When water reaches 100C, it boils, which is called the boiling point, and when it condenses at 0C, it is called the freezing point, which is the usual situation. In some cases, the boiling point temperature and the freezing point temperature change. Boil water in the mountains, and the water boils quickly, but it is not very hot. If you measure it with a thermometer, you will find that the temperature is below 100C. After the water begins to heat, trace amounts of water may enter the gaseous state to form microbubbles, in which water vapor becomes water and water becomes water vapor at the same time. When the temperature rises, the pressure inside the bubble rises, and at a certain point, the water vapor and water are converted into equilibrium (the equilibrium pressure is called the vapor pressure at this temperature). The higher the temperature, the greater the corresponding equilibrium pressure. When the bubble equilibrium pressure is equal to the atmospheric pressure outside, the bubble can rise to the surface of the water, and the water enters a boiling state. The corresponding temperature in this case is the boiling point. If the outside atmospheric pressure decreases, the bubble equilibrium pressure corresponding to the boiling point naturally decreases, and the decrease in equilibrium pressure means that the corresponding temperature decreases. That is, the boiling point temperature drops. Therefore, the magnitude of the air pressure determines the level of the boiling point. Boiling point change of water: 02 atm, 60C, 05 atm, 80C, 1 atm, 100C, 2 atm, 120C. At the bottom of the deep sea, the temperature of the water coming out of the hot springs is 400C.

The purpose of boiling water is to kill bacteria, parasite eggs, etc., in the water. The boiling water in the high mountains has a low temperature and cannot effectively kill bacteria, so it loses the effect of boiling water. Similarly, cooking is not easy to cook. The pressure cooker is that the pot is sealed, and the air pressure inside exceeds the sea level air pressure, and the water must exceed 100C to boil. The pressure cooker has a vent valve, and when the pressure exceeds the limit value, it starts to release steam to ensure that the pressure cooker does not explode.

0C freezes in the water and expands in volume. This is what makes it different from most substances. If the volume expansion of water is restricted, the water cannot freeze. Figure skating can be seen on TV, and these ice dancers have skates on the lower part of their shoes. The blade of the ice blade is very narrow, and the weight of the person directly presses the person into the ice, and the volume of the pressed thin strip of ice decreases, and it becomes water, so that the water acts as a lubrication, and skating is very easy. When the skates leave the freshly formed tank, the water quickly freezes again.

When the air is heated, the volume expands, while the weight does not change, then the density decreases. When the density of the surrounding air does not change, the hot air rises due to buoyancy. In the same way, when the air gets colder, the volume decreases, the density increases, and it sinks. Therefore, when cooking on a fire at home, the pot is placed on top of the fire, so that the heat can be used to the greatest extent. Where there is a heating supply in the north, the radiators are placed under the windows, so that the cold air outside the window comes in and sinks directly to the radiators, where they are quickly heated.

The water is special. At 4C, the heating volume increases. The cooling volume has also increased! In other words, the maximum density of water is not 0C (most liquids are at the freezing point), but 4C. The river is frozen, and the ice itself floats on the surface of the water, and the water under the ice, from top to bottom, the temperature is 0C to 4C, and the fish in the water can stay at the highest temperature, 4C at the bottom of the river. If ice is denser than water, then entire rivers, lakes, and even seas become a world of ice in winter, and most of the complex life in the water cannot breathe and cannot survive. However, when water freezes, it becomes larger and more problematic, and the basic building blocks of life are cells, which are filled with water. When this water freezes, the cell membrane breaks and life cannot survive. (In some amphibians, the cells have antifreeze in their cells, and the cells remain liquid when the whole body is frozen in ice)

These characteristics of water: the best heat storage, the volume of the solid state is larger than that of the liquid, and the density of 4C is the largest. What makes life possible, all life, most of the matter that makes up the body is water. For example, about 70% of the human body is water, and the density of the human body is about the same as water. Therefore, it is relatively easy for people to learn to swim, especially newborn babies who have been living in the water for nine months.

Life on Earth is very tenacious, from the deep sea floor to the top of the mountains, from the 10,000-year-old ice to the salty salt pools. But there is a vast part of the earth, and there is no life, and here is even harsher than the sterilization conditions in the operating room. In the Atacama Desert in northern Chile, there has been no rain for many years, and there is no moisture on the ground. It doesn't seem to be the harshest area, but because there is not a single bit of water, it has become a forbidden area for life.

Summer ice cream, popsicles (are there still any?) Very popular. The moment it reaches your mouth, your tongue feels cold, indicating that the heat is leaving your tongue and entering the ice cream. Slowly the ice cream turns into a sweet liquid, and the temperature does not rise at this point. The heat absorbed by the ice in this process is called the latent heat of melting. When the ice has absorbed the latent heat, it will all turn into water, and then absorb the heat before the water heats up. The same is true for boiling water, when the water reaches 100C, it absorbs heat and becomes 100C water vapor. The temperature remains the same. If there is no calorie supplement, it will not be able to change into water vapor. This part of the heat becomes the latent heat of gasification. 80 calories can raise 1 gram of water from 0C to 80C, but only 1 gram of ice can turn into 1 coco. And 1 gram of 100C water becomes 100C water vapor for 540 calories!

As we mentioned earlier, hurricanes, also known as typhoons, are caused by the latent heat released by water vapor. On tropical seas, the water temperature is high enough (>27C) and the hot water is deep enough (>50m) to be the source of energy for the hurricane. At this surface, a huge package of hot gas leaves the surface, creating a local vacuum, where the air pressure drops, forming the center of the hurricane. The surrounding air rushed to replenish. The incoming air currents are deflected by the Coriolis force, forming a large vortex counterclockwise (northern hemisphere) or clockwise (southern hemisphere). A large number of updraft packets carrying water vapor rapidly drop in temperature in the air, and part of the water vapor condenses into water, releasing a large amount of latent heat of vaporization. This latent heat takes the form of wind, with high wind speeds leading to low air pressure (Bernoulli's principle), and low pressure leading to increased evaporation, which in turn causes more water vapor to condense. Most of the heat released drives the updrafts, which raise the height of the storm clouds and further accelerate condensation. This is a self-driving process that makes hurricanes stronger and stronger, with a range of hundreds of kilometers, acting as a powerful heat sink. If the surface water is not hot enough and the amount of hot water is not enough, it will not be sustainable. As a hurricane moves, the sea surface temperature generally drops due to the constant absorption of heat from the seawater. When the hurricane enters land and there is no longer a source of heat, the hurricane slowly dissipates. Of course, before dissipating, the energy accumulated in the front appears in the form of destruction.

A similar form on land is a tornado, which of course cannot be compared to a hurricane. It is also triggered by large-scale updrafts (much smaller than those in the sea, less than 100 meters), most of which rotate in the same direction as hurricanes. Due to the small effective range of the scale relative to the Coriolis force, it is possible to rotate in the opposite direction. In addition, there is a lack of thermal supplementation, the duration is short, and the distance of movement is between a few kilometers and tens of kilometers.

Ponder:

1. When we cook, the common temperature for steaming is 100C. The stir-fry temperature exceeds 250C, and the grilling temperature exceeds 500C. So can you cook cooked rice at low temperatures? For example, 60C stir-fry, 50C cooking.

2. When the submarine launches the missile, it keeps heating the water at the bottom of the missile shaft, and after it all turns into water vapor, it continues to heat, and the pressure is getting bigger and bigger. Finally, the missile was ejected from the silos, rushed out of the water, and then ignited. In a similar situation, the launch of fish and mine, and the ejection of carrier-based aircraft on an aircraft carrier, are carried out with water vapor. So when the space shuttle is launched, there is also a large amount of water under the launch port, and a large amount of boiling water vapor gushes out during the launch, what is the role of this? *

3When using hot water, if you accidentally pour a small amount of hot water on your skin, your skin will soon turn red. But if you accidentally let the steam spray on your skin, it is easy to get big blisters.

4Find a large piece of ice in winter, find a thin wire, hang the wire on the ice, tie a heavy object at both ends, such as dumbbells, and observe the wire. Can wire stay on ice all the time?

5. Permafrost is a perennial temperature lower than 0C, and the moisture inside the soil is completely stored in the form of ice, which is distributed in the alpine zone. In China, permafrost is generally covered with normal soil ranging from a few meters to tens of meters thick. The permafrost retains moisture, and the water of the soil above is blocked by the permafrost and cannot penetrate and flow away.

The high water table makes it easy to form wetlands and meadows. As the climate warms, permafrost disappears, the water table drops, the upper soil is unable to retain moisture, and wetland meadows are gradually desertified. In the Qinghai-Tibet Plateau and the Great Khing'an Mountains, it is easy to see such a scene. If widespread permafrost disappears, how will the surface topography change?

6 household air conditioners, all installed near the top of the room. radiators, are installed under the windows. Why?

7 Summer afternoons, small cyclones can often be observed. In an area of the ground, a whirlwind suddenly appeared, blowing up a small amount of dust. The movement of the dust in the wind shows the rotation and path of the whirlwind. So what determines the direction of rotation of the cyclone at this moment? If you look closely at the initial area of the cyclone, what is the difference from other areas?

8 gliders, without power, glide through the air. It stands to reason that the height should be lower and lower. But in fact, an experienced pilot can maintain an altitude without dropping, or even getting higher and higher, how does he do it? *

9 Sometimes, when a tornado passes over a river or lake, it sucks up a lot of water and even carries some fish and amphibians. In another area, it rained animals. So will it bring animals to an area where the living environment is very different?

10 Under normal conditions, 0c water starts to freeze. If the water is very pure and free of any impurities, then to -70C, the water will not freeze, which is called supercooled water, as shown in the figure on the right. Supercooled water is sprayed from the water pipe, and after contact with impurities, it freezes instantly. There are sometimes hailstorms in the summer. This is a strong convective air flow in the high air, and the small water droplets cannot land under the action of the air flow, and they merge into large water droplets before they fall. When the temperature is lower than 0C, it will condense into ice particles, which may rise again due to the influence of air currents during the fall, and accumulate water droplets many times and gradually increase. When the size increases to the point where the air flow can no longer be maintained, it falls down and becomes hail. What are the factors that affect the size of the hail?

11 In a naval battle, when a certain ship is about to sink, the surrounding crew members rush to leave the waters near the ship, why?

12 In film and television programs, when a bullet is shot into the water, we see a trajectory formed by bubbles, and this trajectory is the path through which the bullet passes. But the bubbles slowly disappeared and did not rise to the surface of the water. Combine the content of the last part of the fourth section above to explain the reasons for the formation of bubbles. *

13 The heat of the sea comes from the sun, and the energy provided by the sun varies at different latitudes, and the equatorial region is the strongest in the average sense. Since the ocean currents flow from east to west near the equator, then these currents continue to be heated by the sun, and the temperature increases slowly, about one degree per longitude, increasing by 01c, and when the ocean current moves in the direction of the poles, it dissipates heat to the surrounding environment, and decreases by about 03c per degree of latitude When the ocean current enters the high latitude region and flows from west to east, due to the low ambient temperature, the current still maintains a cooling temperature, and the amplitude is also 01c per longitude. In the same way, when ocean currents move from the poles to the equator, the currents absorb heat from the surrounding environment and the temperature remains at an increase of 03C per latitude. From this, it can be concluded that hurricanes tend to form in the western part of the ocean.

Between two objects with different temperatures, heat transfer occurs. There are 3 forms of heat transfer.

1 Convection, which occurs inside the same type of fluid. For example, air convection, water convection. The heat flow rises, the cold flow falls, there is no exchange, and finally the temperature is the same, ending the heat transfer. The atmosphere has a troposphere, and the oceans have ocean currents and circulation, which specialize in heat redistribution, resulting in the Earth's diverse climate and environment. The distribution of heat also brings about the distribution of water, transporting water from the ocean to land, completing the prerequisites for life to be on land.

2. Conduction, which occurs between objects that are in contact with each other, and at the same time does not meet the convection conditions. Heat is transferred in a conductive manner between solids and between solids and fluids. A hot bath can rejuvenate a person who is frozen and languid. The Inuit also dissipate heat in this way. Different objects have different properties of heat conduction, and metals are generally better. Ceramics and leather are relatively poor. The best thermal conductivity is silver, which is 9 times that of iron. Aluminum is also good, 44 times more than iron. Silver cookware is a bit expensive, and ordinary people can't afford it. However, there is an advantage to using silver as bowls and plates, which can kill some bacteria. Iron, although the conductivity is not the best, but it is cheap and sufficient, so most of the pots we cook use iron. Aluminum is light and transfers heat quickly, so why not use aluminum? There is an oxide film on the surface of aluminum, which can prevent further oxidation of aluminium and prevent the human body from ingesting aluminum. However, when brushing the pot, use an iron brush to scrape, and some acidic substances can easily damage the membrane when cooking. Therefore, the woks are basically made of iron pots. The pressure cooker is generally stewed and boiled, and is made of aluminum, which is lightweight and easy to use, and at the same time, it is not easy to damage the oxide film on the surface. The human body needs a lot of metals, but aluminum is not one of them, so try to consume as little as possible.

3 radiation, which occurs between objects that do not come into contact. For example, the sun radiates through guò, which brings a lot of heat to the earth. When air is convection, hot air enters the air and radiates heat into space. And all objects, as long as the temperature is not -27315C, radiate outward, the difference is only the amount of radiation. Radiation and convection are the most feasible forms of heat in the universe, such as convection on the surface and interior of the sun, and radiation on the outside. There is very little conduction, because the vast majority of perceptible matter in the universe exists in fluid form.

Typically, heat transfer is a combination of multiple forms. When boiling water, there is conduction and radiation between the heat source and the kettle, conduction between the kettle and the water, and convection between the water. In winter, the fire is radiated and convection. Barbecue, is radiating and conducting.

Heat is generated in a variety of ways: combustion, nuclear reactions, compression, friction. Usually we cook, using natural gas, liquefied gas, coal, firewood, straw, etc., and the combustion produces a lot of heat to carry out. There is a gentle way of burning and a violent way. Combustion types such as automobile engines (burning oil), steam engines (burning coal), cooking, etc., are violent methods, and the fuel (the material being burned) burns quickly, accompanied by light, sound, and other effects, generating a large amount of heat. Gentle ways, like our bodies. We consume a certain amount of food every day, and these foods are digested and turned into substances that can be processed by the body's tissues, and we experience burning. Part of the energy produced is used to maintain our body temperature and ensure our mobility, and the other part is stored in zài cells. If these substances are not consumed, the excess will be stored in the form of fat, and the body will slowly gain weight. All plants and animals are burned gently inside. Many of the batteries used in the space shuttle today are fuel cells, which burn hydrogen to generate electricity, and this combustion is also a mild way. The sun and other stars are all generated by the reaction of the nucleus to produce heat, which is a common phenomenon in the universe, and burning is a rare phenomenon. And on Earth, combustion is going on all the time, while nuclear reactions take place in places such as nuclear power plants, nuclear tests, nuclear attacks, and nuclear power rarity. Contrary to the general situation in the universe, as life is known only to occur on Earth! In general, solids and liquids are difficult to compress, and gases are easily compressed. Bicycle pumps and grip rubber rings can feel the heat generated by compression after many uses. The solid tires of the armored car, all parts of which are cyclically compressed when driving, become piping hot after a long drive. Friction produces heat, which is a common phenomenon in life. The earliest application was to drill wood for fire, which is a prehistoric way of making fire, although it seems inconvenient now, but it is a transition from passive to active fire (the traditional method of fire by the Inuit is to drill wood for fire). In most cases, friction does not generate much heat, but it can cause a lot of trouble. Since the Industrial Revolution, lubricants have been widely needed to reduce friction.

Ponder:

1 The convection of air and water in nature is widely existed, and the indoor is mainly forced convection. The range hood in the kitchen, the exhaust fan in the hall, and the central air conditioner in the building all consume electricity. But natural convection can be used to generate electricity, understand the current state of new energy, and list what are the natural convection power generation methods?

2Go to a banquet, usually cold dishes and hot dishes. Most of the observation bowls and plates are made of ceramic materials. Earlier, wooden cutlery was also widely used, why? In addition, in ancient Rome, lead tableware was widely used, resulting in lead poisoning was very common.

3. Night vision devices (infrared imagers) can observe the surrounding environment when there is no visible light at night, why is it possible?

4. The thermos flask is insulated, the airtightness isolates the possibility of heat convection, the approximate vacuum in the cork and the glass bottle reduces the heat conduction, and the inner membrane of the bottle is silver-plated (magnesium) to block the heat radiation. Fill half a bottle of boiling water in the thermos, if you plug the cork immediately, soon the cork will fly out. If you wait a while and then plug it on. After a long time, the cork is not easy to remove. Why?

5. There is a lot of heat generation in the city. The chimneys of factories, the exhaust fumes of automobiles, the exhaust vents of air conditioners, the stoves of kitchens, and our exhalations all contribute to the heat. There is less vegetation in the city, there are many concrete buildings, and there is a lot of waste in the air, so solar radiation is more likely to accumulate. As a result, the average air temperature in the city is higher than in the suburbs. This is called a heat island. There is a similar effect in the countryside, but the heat island is much smaller. When is the heat island effect greater? Under what circumstances does the heat island effect become smaller?

6. Where there is coal and abundant water resources, there are often thermal power plants. Its landmark building is a cooling tower with curved sides and a steaming façade on top. Letting this hot water cool down is a big waste. In the north, these hot waters can be used for heating in winter. In addition, hot water can be used to warm up tropical fish, such as tilapia. It is a very cost-effective fish.

7. The heat burned by different foods varies greatly, and the heat generated by the combustion of a certain substance of a fixed weight is called calorific value. Usually the largest calorific value of food is cream, which is about the same as anthracite. Peanuts also have a high calorific value, although not as good as alcohol and higher than pine. White sugar is also good, slightly worse than pine. Surprisingly, lean meat has a very low calorific value, about the same as rice and about a quarter of that of pine. Scrambled eggs have 30% higher calorific value than boiled eggs. Foods with high fat content or fried can be found with high calorific value. A high calorific value of food does not equal a high level of nutrition. And if the food is too high in calories and exceeds the needs of the human body, the body will gain weight. While the human body needs heat to maintain body temperature and activity, the human body itself requires other types of substances to function. Nutritious refers to foods that produce calories, substances that are necessary for metabolism, and substances that maintain the ability to protect themselves. Mixed rice flour (calories, vitamins), vegetables (cellulose, vitamins), meat (animal protein), fruits (vitamins, trace elements), legumes (vegetable protein, durable starch), and fatty and lean meats are eaten. When there is a single type of food, a specific diet is formed. Inuit people have limited access to plant-based foods (vegetables) and are unable to supplement with vitamins in this way. But the meat they ate was very low, and the vitamins inside were not destroyed, so they were unharmed. Westerners often eat steaks that are medium-rare or medium-rare, or medium-rare, with blood streaks, and there may also be a habitual factor in this.

8 In winter, the hands are cold, rub each other vigorously, and the hands will be warmed up for a while. Is it the result of frictional heat generation?

9 Long-distance buses, especially those operating on mountain roads, generally have a large bucket in the car, which continuously drips into the brake pads. Why?

10. When exploring outdoors, it is necessary to carry a metal film heat reflective cloth. When the clothes are soaked and lose their warmth and need to be kept warm, this lightweight heat-reflective clothing can effectively prevent the rapid drop of body temperature.

(End of chapter)