Superb Energy in the Atmosphere
第 1 單元，第 1 課

Particles in Motion運動中的粒子

這課一眼看
Particles are always moving粒子一直在運動
  • random motion隨機運動: Movement of particles in all directions and at different speeds.
  • diffusion擴散: Movement of particles from an area of higher concentration to an area of lower concentration.
  • thermodynamics熱力學: The study of heat and its relationship to energy.
  • joule焦耳: The SI unit of energy.
Temperature溫度
    Particles in solids, liquids, and gases固體、液體、氣體中的粒子
      Energy and mass能量與質量
        1Particles are always moving粒子一直在運動

        ARandom motion and diffusion隨機運動與擴散

        1. All matter is made of tiny particles that never stop moving, even when an object looks perfectly still. In liquids and gases, particles bump into and flow past each other in random motion: movement in all directions at different speeds.所有物質都由微小的粒子構成，這些粒子永不停止運動，即使物體看起來完全靜止。在液體和氣體中，粒子以隨機運動互相碰撞、流過彼此，也就是朝各個方向、以不同速度移動。
        2. A drop of food coloring in still water slowly spreads out because water particles keep hitting it. This is diffusion: particles moving from an area of higher concentration to an area of lower concentration until the concentration is the same everywhere.把一滴食用色素滴進靜止的水裡，色素會慢慢散開，因為水分子不斷撞擊它。這就是擴散：粒子從濃度高的地方移到濃度低的地方，直到各處濃度相同。
        3. You can smell lunch from down the hall because gas particles diffuse. Gas particles travel in straight lines until they collide with something, which changes their speed and direction.你在走廊另一端也能聞到午餐的味道，因為氣體粒子會擴散。氣體粒子沿直線前進，直到撞上東西，才改變速度和方向。
        練習 1

        BSpeed and kinetic energy速度與動能

        1. Adding energy, for example by heating, makes particles move faster, so dye spreads faster in hot water than in cold water. The energy of motion is kinetic energy; the faster particles move, the more kinetic energy they have.加入能量（例如加熱）會讓粒子移動得更快，所以色素在熱水中比在冷水中擴散得快。運動的能量稱為動能；粒子移動得越快，動能越大。
        2. In particle diagrams, motion lines show speed: more lines mean faster particles.在粒子模型圖中用動線表示速度：線越多，代表粒子越快。
        注意
        The study of heat is called thermodynamics. James Prescott Joule argued that heat is the motion of particles; the unit of energy, the joule (J), is named after him.研究熱的學問稱為熱力學。焦耳主張熱是粒子的運動；能量的單位「焦耳（J）」就是以他命名。
        練習 2
        2Temperature溫度

        AThermal expansion and contraction熱脹與冷縮

        1. When a material warms, its particles move faster, collide more often, and push farther apart, so its volume increases. This is thermal expansion. When particles slow down, they take up less space: thermal contraction.物質變熱時，粒子移動得更快、碰撞更頻繁，彼此被推得更開，體積就變大，這是熱膨脹。粒子變慢時占的空間變小，這是熱收縮。
        練習 3

        BMeasuring temperature測量溫度

        1. temperature is a measure of the average kinetic energy of the particles in a material. Higher temperature means faster particles on average.溫度是物質中粒子平均動能的量度。溫度越高，代表粒子平均移動得越快。
        2. Thermometers work by thermal expansion: the liquid inside expands as it warms and rises in the tube.溫度計利用熱膨脹原理：裡面的液體變熱就膨脹，在細管中上升。
        3. A temperature scale uses two fixed points with even divisions between them. The Celsius scale uses 0 °C (water freezes) and 100 °C (water boils). The Kelvin scale starts at absolute zero (0 K), where particles would stop moving and have no kinetic energy.溫標用兩個固定點，中間平均分格。攝氏溫標用 0 °C（水結冰）和 100 °C（水沸騰）。克氏溫標從絕對零度（0 K）開始，在這個溫度粒子會停止運動、沒有動能。
        Temperature scales溫標
        Celsius (°C)攝氏（°C）Fahrenheit (°F)華氏（°F）Kelvin (K)克氏（K）
        Water boils水沸騰100100212212373373
        Water freezes水結冰003232273273
        Absolute zero絕對零度−273−273−460−46000
        練習 4
        3Particles in solids, liquids, and gases固體、液體、氣體中的粒子

        AHow particles move in each state各狀態粒子的運動方式

        1. Gas particles move fast, spread far apart, and have a lot of kinetic energy. Liquid particles are close together but slide past each other. Solid particles only vibrate in place, so they have less kinetic energy. At the same temperature, however, particles of all three states have the same average kinetic energy — that average is exactly what temperature measures. The differences described here are about how freely the particles can move.氣體粒子移動快、彼此距離遠、動能大。液體粒子靠得很近，但可以互相滑動。固體粒子只能在原地振動，所以動能較小。不過在相同溫度下，三態粒子的平均動能其實相同——溫度量的正是這個平均。這裡說的差異，指的是粒子能多自由地移動。
        2. All three states expand when heated. Expansion in solids is small and harder to notice, but a metal ring that fits over a ball when cold can be too small when the ball is heated.三種狀態加熱時都會膨脹。固體的膨脹很小、不容易察覺，但冷的時候能套過金屬球的金屬環，在金屬球加熱後就套不過去了。
        3. Engineers plan for thermal expansion. Bridges have expansion joints that let metal grow in summer and shrink in winter, and concrete sidewalks have gaps so they do not crack.工程師設計時會考慮熱膨脹。橋梁有伸縮縫，讓金屬夏天伸長、冬天縮短；水泥人行道也留有縫隙，避免裂開。
        練習 5
        4Energy and mass能量與質量

        AMore particles, more energy粒子越多，能量越多

        1. Two samples at the same temperature have the same average kinetic energy, but the one with more mass has more particles and therefore more total energy. 100 g of water at 30 °C contains five times as many particles, and more total energy, than 20 g at 30 °C.兩個溫度相同的樣本，平均動能相同；但質量較大的樣本粒子較多，所以總能量較多。30 °C 的水 100 g 所含的粒子是 20 g 的五倍，總能量也比較多。
        自我檢查
        You add 20 g of 50 °C water to one beaker and 100 g of 30 °C water to another. Each beaker started with 200 g of room-temperature water. Can you predict which ends warmer just from the starting temperatures?你在一杯中加入 50 °C 的水 20 g，另一杯加入 30 °C 的水 100 g；兩杯原本都有 200 g 室溫水。能只看加入的水溫就判斷哪杯最後比較熱嗎？
        看答案
        No. Both temperature and mass matter. The hotter water is a small amount, so it brings less total energy than you might expect; you must consider how much energy each addition carries.不能。溫度和質量都會影響。較熱的水量很少，帶進去的總能量可能沒有想像中多，必須同時考慮每次加入的能量有多少。
        練習 6

        這課的重點字

        • random motion隨機運動
        • diffusion擴散
        • thermodynamics熱力學
        • joule焦耳
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