HKDSE Physics Core
Chapter 1: Temperature, Heat and Internal Energy | 溫度、熱量與內能
Billy Sir’s Smart Notes: Master Temperature Scales, Heat Capacity, and Energy Transfer.
由中大物理系碩士 Billy Sir 編寫，助你極速掌握溫標、熱容量及能量轉移。
1. Temperature Scale & Calibration | 溫標與溫度計的校準
Temperature is a measure of the degree of hotness of an object. The Celsius scale (\( ^\circ\text{C} \)) is commonly used. 溫度是量度物體冷熱程度的物理量。最常用的是攝氏溫標。
🌡️ Calibration of a Thermometer | 校準溫度計
To calibrate a thermometer, we need two fixed points: 要校準溫度計，我們需要兩個固定點：
- Ice Point (0 \( ^\circ\text{C} \)): The temperature of pure melting ice at standard atmospheric pressure. (冰點：標準大氣壓下純冰熔化的溫度)
- Steam Point (100 \( ^\circ\text{C} \)): The temperature of steam over pure boiling water at standard atmospheric pressure. (汽點：標準大氣壓下純水沸騰時蒸汽的溫度)
The interval between these two points is divided into 100 equal parts. 將這兩點之間的距離分成100等份，每份為1度。
2. Different Types of Thermometers | 不同類型的溫度計
| Type (類型) | Thermometric Property (測溫屬性) | Features / Applications (特點 / 應用) |
|---|---|---|
| Liquid-in-glass 玻璃液體溫度計 |
Volume of liquid (Mercury or Alcohol) (液體體積) | Common for daily use; direct reading. (日常使用，直接讀取) |
| Resistance Thermometer 電阻溫度計 |
Electrical resistance of a metal wire (金屬線的電阻) | Very accurate; wide range; slow response. (非常準確，量程廣，反應較慢) |
| Thermistor 熱敏電阻溫度計 |
Electrical resistance of a semiconductor (半導體的電阻) | Fast response; highly sensitive over a small range. (反應快，在小範圍內靈敏度高) |
| Infra-red Thermometer 紅外線溫度計 |
Infrared radiation emitted by object (物體發出的紅外線輻射) | Non-contact; very fast response (e.g., ear thermometer). (非接觸式，反應極快) |
3. Internal Energy and Heat | 內能與熱量
🔥 Definitions | 定義
- Internal Energy: The sum of the kinetic energy (due to random motion) and potential energy (due to intermolecular forces) of all particles in an object. (內能：物體內所有粒子的動能和勢能的總和。)
- Heat: The energy transferred from one body to another solely due to a temperature difference. Heat always flows from a hotter object to a colder one. (熱量：純粹因溫度差異而從一個物體轉移到另一個物體的能量。熱量總是從高溫物體流向低溫物體。)
4. Heat Capacity vs Specific Heat Capacity | 熱容量與比熱容量
| Property (屬性) | Heat Capacity, \( C \) (熱容量) | Specific Heat Capacity, \( c \) (比熱容量) |
|---|---|---|
| Definition 定義 |
Energy required to raise the temperature of an object by \( 1 ^\circ\text{C} \). (使整個物體溫度升高 1°C 所需的能量) | Energy required to raise the temperature of 1 kg of a substance by \( 1 ^\circ\text{C} \). (使 1 kg 物質溫度升高 1°C 所需的能量) |
| Formula 公式 |
\[ E = C \Delta T \] | \[ E = m c \Delta T \] |
| Unit 單位 |
\( \text{J } ^\circ\text{C}^{-1} \) | \( \text{J kg}^{-1} \ ^\circ\text{C}^{-1} \) |
5. Mixing of Substances | 物質混合
When two substances at different temperatures are mixed, heat transfers from the hotter substance to the colder one until they reach thermal equilibrium (same final temperature). 當兩種不同溫度的物質混合時，熱量會從高溫物質轉移到低溫物質，直到達到熱平衡（最終溫度相同）。
⚖️ Conservation of Energy | 能量守恆
Assuming no heat is lost to the surroundings: (假設沒有熱量流失到周圍環境：)
(Where \( T_1 \) is the initial high temp, \( T_2 \) is the initial low temp, and \( T_f \) is the final mixture temp. \( T_f \) 是最終混合溫度。)
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