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  • 热能、温度和热能

    Erupting basalt lava with bright orange colors, indicating high temperature at Kilauea volcano.

    The of basalt lava at Kilauea (Hawaii) reaches 1,160 degrees Celsius (2,120 degrees Fahrenheit). A crude estimation of temperature can be determined by looking at the color of the rock: orange-to-yellow colors are emitted when rocks (or metals) are hotter than about 900 degrees Celsius; dark-to-bright cherry red is characteristic as material cools to 630 degrees Celsius; faint red glow persists down to about 480 degrees Celsius. For comparison, a pizza oven is commonly operated at temperatures ranging from 260 to 315 degrees Celsius.
    ::在Kilauea(哈瓦伊)的玄武岩熔岩达到1,160摄氏度(2,120摄氏度),对温度的粗略估计可以通过观察岩石的颜色来确定:在岩石(或金属)温度超过900摄氏度以上时,会释放橙色至黄色的颜色;暗对亮樱桃红色是物质冷却到630摄氏度的特征;微红光持续到大约480摄氏度的特征;相比之下,一个披萨烤箱通常在260摄氏度至315摄氏度的温度下操作。

    Heat, Temperature, and Thermal Energy Transfer
    ::热热、温度和热能转移

    The first theory about how a hot object differs from a cold object was formed in the 18th century. The suggested explanation was that when an object was heated, an invisible fluid called “caloric” was added to the object. Hot objects contained more caloric than cold objects. The caloric theory could explain some observations about heated objects (such as that the fact that objects expanded as they were heated) but could not explain others (such as why your hands got warm when you rub them together).
    ::第一个关于热物体与冷物体不同之处的理论是在18世纪形成的。建议的解释是,当物体变暖时,在物体上添加了一种叫做“热液”的无形液体。热物体含有比冷物体更多的热量。热物质理论可以解释一些关于加热物体的观察结果(例如,物体变热后会膨胀),但却无法解释其他物体(例如,为什么把物体一起擦在一起,你的手会变暖)。

    In the mid-19th century, scientists devised a new theory to explain . The new theory was based on the assumption that matter is made up of tiny particles that are always in motion. In a hot object, the particles move faster and therefore have greater . The theory is called the kinetic-molecular theory and is the accepted theory of heat. Just as a baseball has a certain amount of kinetic energy due to its mass and , each molecule has a certain amount of kinetic energy due to its mass and velocity. Adding up the kinetic energy of all the molecules in an object yields the of the object.

    ::在19世纪中叶,科学家们设计了一个新的理论来解释。新的理论是基于一个假设,即物质是由始终在运动中的微粒组成的微粒组成。在一个热天体中,粒子移动得更快,因此变得更大。这个理论被称为动能分子理论,是公认的热理论。就像棒球由于其质量而具有一定的动能一样,每个分子由于其质量和速度而具有一定的动能。加上一个物体中所有分子的动能,就可以产生物体。

    When a hot object and a cold object touch each other, the molecules of the objects collide along the surface where they touch. When higher kinetic energy molecules collide with lower kinetic energy molecules, kinetic energy is passed from the molecules with more kinetic energy to those with less kinetic energy. In this way, heat always flows from hot to cold and heat will continue to flow until the two objects have the same temperature. The movement of heat from one object to another by molecular collision is called .
    ::当热物体和冷物体相互触碰时,物体的分子在它们接触的表面相撞。当较高的动能分子与较低动能分子相撞时,动能能量从具有较强动能的分子传到动能较弱的分子。这样,热量总是从热到冷,热量将继续流动,直到两个物体有相同的温度。用分子碰撞从一个物体向另一个物体的热量移动被称为分子碰撞。

    Heat is the that flows as a result of a difference in temperature.  We use the symbol  Q for heat. Heat, like all , is measured in joules .
    ::热是温度差异造成的流动。我们用符号Q作为热量。热和热一样,用焦耳测量。

     

     

    The temperature of an object is a measurement of the average kinetic energy of all the molecules of the object.  You should note the difference between heat and temperature. Heat is the sum of all the kinetic energies of all the molecules of an object, while temperature is the average kinetic energy of the molecules of an object. If an object was composed of exactly three molecules and the kinetic energies of the three molecules are 50 J, 70 J, and 90 J, the heat would be 210 J and the temperature would be 70 J.
    ::对象的温度是测量对象所有分子的平均动能。 您应注意温度和热的差别。 热量是物体所有分子的所有动能的总和, 而温度是物体分子的平均动能。 如果物体由三个分子组成, 三个分子的动能为50焦耳、 70焦耳和90焦耳, 热量为210焦耳, 温度为70焦耳。

     

     

    The terms hot and cold refer to temperature. A hot object has greater average kinetic energy but may not have greater total kinetic energy. Suppose you were to compare a milliliter of water near the boiling point with a bathtub full of water at room temperature. The bathtub contains a billion times as many water molecules, and therefore has a higher total kinetic energy and more heat. Nonetheless, we would consider the bathtub colder because its average kinetic energy, or temperature, is lower.
    ::热和冷是指温度。 热对象具有更高的平均动能,但可能没有更大的动能。 假设你将沸点附近的一毫升水与室内温度下充满水的浴缸作比较的话。 浴缸中水分子数是水分子数的十亿倍,因此总动能和热度都更高。 尽管如此,我们还是认为浴缸更冷,因为它的平均动能或温度较低。

    Adjust the temperature slider in the simulation below to visualize its effect on the average kinetic energy of the molecules making up the Golden Gate Bridge:
    ::调整以下模拟中的温度滑动滑动器,以直观地显示其对构成金门大桥的分子的平均动能的影响:

     

     

    Temperature Scales: Celsius and Kelvin
    ::温度尺度:摄氏度和开尔文

    A thermometer is a device used to measure temperature. It is placed in contact with an object and allowed to reach thermal equilibrium with the object (they will have the same temperature). The operation of a thermometer is based on some property, such as volume, that varies with temperature. The most common thermometers contain liquid mercury, or some other liquid, inside a sealed glass tube. The liquid expands and contracts faster than the glass tube. Therefore, when the temperature of the thermometer increases, the liquid volume expands faster than the glass volume, allowing the liquid to rise in the tube. The positions of the liquid in the tube can then be calibrated for accurate temperature readings. Other properties that change with temperature can also be used to make thermometers; liquid crystal colors and electrical conductivity change with temperature, and are also relatively common thermometers. 
    ::温度计是一种用于测量温度的装置,它与物体接触,并允许与物体达到热平衡(它们具有相同的温度)。温度计的操作基于某些特性,例如体积随温度变化而变化。最常见的温度计在密封的玻璃管内含有液体汞或其他液体。液体的膨胀和结合速度比玻璃管更快。因此,当温度计温度升高时,液体体积的膨胀速度比玻璃体积快,使液体在管内能够上升。然后,可以对管内的液体位置进行精确温度读数校准。与温度变化有关的其他特性也可以用来制作温度计;液体晶体颜色和电导力变化与温度变化相对常见。

    The most commonly used temperature scale in the United States is the Fahrenheit scale. However, this scale is rarely used throughout the world; the metric temperature scale is Celsius. This scale, based on the properties of water, was devised by the Swedish physicist, Anders Celsius (1704 – 1744). The freezing point of water is 0°C and the boiling point of water was assigned to be 100°C.  The kinetic energies between these two points was divided evenly into 100 “degrees Celsius”. 
    ::在美国,最常用的温度尺度是法赫里内海特(Fahrenheit ) , 然而,这一尺度在全世界很少使用; 测量温度尺度为摄氏度。 这一尺度基于水的特性,由瑞典物理学家安德斯摄氏(1704 - 1744)。 冷水点为0°C,沸水点为100°C。 这两个点之间的动能均匀地分为100“摄氏度 ” 。

    The Kelvin or “Absolute” temperature scale is the scale often used by chemists and physicists. It is based on the temperature at which all molecular motion ceases; this temperature is called absolute zero and is 0 K. This temperature corresponds to -273.15°C exactly, but we can round to -273 °C when performing calculations and conversions.   Since absolute zero is the coldest possible temperature, there are no negative values on the Kelvin temperature scale. Conveniently, the Kelvin and Celsius scales have the same definition of a degree, which makes it very easy to convert from one scale to the other. The relationship between Celsius and Kelvin temperature scales is given by:
    ::Kelvin或“Absolute”温度尺度是化学家和物理学家经常使用的尺度。它基于所有分子运动停止的温度;这种温度被称为绝对零,为0K。这种温度与273.15°C完全对应,但在进行计算和转换时,我们可以圆到-273°C。由于绝对零是可能最冷的温度,因此Kelvin温度尺度上没有负值。很容易的是,Kelvin和Cozel的尺度对程度有相同的定义,因此很容易从一个尺度转换到另一个尺度。摄氏和Kelvin的温度尺度之间的关系如下:

    K = °C + 273
    ::K=°C+273

    On the Kelvin scale, water freezes at 273 K and boils at 373 K. 
    ::在开尔文级,水冻结在273K,沸腾在373K。

    Example 
    ::示例示例示例示例

    Convert 25°C to Kelvin.
    ::将25°C转换为开尔文。

    K = °C + 273 = 25°C + 273 = 298 K
    ::K = °C + 273 = 25°C + 273 = 298 K

    Cookies baking in an oven, decorated for the holidays on baking sheets.

    Yummy! These cookies look delicious. But watch out! They just finished baking in a hot oven, so the cookie sheet is too hot to handle without an oven mitt. Touching the cookie sheet with bare hands could cause a painful burn. However, the air inside the oven doesn’t hurt. How can this be? Explore the Hot Oven simulation below to find out:
    ::美味! 这些饼干看起来很美味。 但是小心! 它们刚在烤箱中烤好, 所以没有烤箱手套, 饼干床单太热了, 处理不了。 光手触摸饼干床单可能会造成痛苦的烧伤。 但是, 烤箱中的空气并不痛。 这怎么可能? 试探下面的热奥文模拟以了解 :

     

     

    Further Reading
    ::继续阅读

    Summary
    ::摘要

    • The thermal energy, or heat, of an object is obtained by adding up the kinetic energy of all the molecules within it.
      ::物体的热能或热能是通过将其中所有分子的动能加在一起获得的。
    • Temperature is the average kinetic energy of the molecules.
      ::温度是分子的平均动能。
    • Absolute zero is the temperature where molecular motion stops and is the lowest possible temperature.
      ::绝对零是分子运动停止的温度 并且是最低的温度
    • Zero on the Celsius scale is the freezing point of water and 100°C is the boiling point of water.
      ::摄氏度零度是水的冰点,100°C是沸水点。
    • The relationship between Celsius and Kelvin temperature scales is given by K = °C + 273.
      ::摄氏和开尔文温度尺度之间的关系由K = °C + 273给出。

    Review
    ::回顾

    1. Convert 4.22 K to °C.
      ::将4.22K转换为°C。
    2. Convert 37°C to K.
      ::将37°C转换为K
    3. If you had beeswax attached to one end of a metal skewer and you placed the other end of the skewer in a flame, what would happen after a few minutes?
      ::如果你把蜜蜂壳的一端附着在金属切口上, 把另一端放在火焰中, 几分钟后会发生什么?
    4. Which contains more heat, a coffee cup of boiling water or a bathtub of room temperature water?
      ::里面有更热的 开水的咖啡杯 还是室内温水的浴缸?

    Explore More
    ::探索更多

    Use this resource to answer the questions that follow.  
    ::使用此资源回答下面的问题 。

     

     

    1. Which material was a better conductor of heat?
      ::哪一种材料更能导热?
    2. Explain why metals feel cold even when they are at room temperature.
      ::解释为什么金属即使在室温下也感到寒冷。

     

    Resources
    ::资源

    This MIT video examines the phenomenon of Joule heating through the perspective of a blender, reproducing the experiment of the English physicist James Prescott Joule.
    ::这段麻省理工学院影片从搅拌机的角度审视了Joule供暖现象,