Specific Heat and Thermal Conductivity · 比热容与热导率
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| specific heat capacity/spəˈsɪfɪk hiːt kəˈpæsɪti/ | 比热容 | bǐ rè róng |
The sand scorches your feet, but the sea stays cool
- On a summer beach the sand burns your feet while the water beside it is refreshingly cool.
- Same sunshine — but water needs far more energy to warm up than sand does.
- How much heat a material needs per degree is its specific heat capacity 比热容.
- A related idea, thermal conductivity, sets how fast heat travels through it.
沙子烫脚,海水却清凉
- 夏日海滩上,沙子烫脚,而旁边的海水却清凉宜人。
- 同样的阳光——但水比沙子需要多得多的能量才能变暖。
- 一种材料每升高一度所需的热量,是它的比热容。
- 一个相关的概念,热导率,决定热穿过它的快慢。
The heat equation
- The heat to change a temperature is $Q = mc\Delta T$.
- $m$ is the mass, $c$ the specific heat capacity, and $\Delta T$ the temperature change.
- A high $c$ (like water) means a lot of energy per degree — it heats and cools slowly.
- A low $c$ (like metal) means little energy per degree — it heats up fast.
热量方程
- 改变温度所需的热量是 $Q = mc\Delta T$。
- $m$ 是质量,$c$ 是比热容,$\Delta T$ 是温度变化。
- 高 $c$(如水)意味着每度需要很多能量——它加热和冷却都很慢。
- 低 $c$(如金属)意味着每度需要很少能量——它加热得很快。
Heat different materials · 加热不同材料
Change the material and mass and see how much heat is needed for a given temperature rise. · 改变材料和质量，观察使给定温升所需的热量。
How much heat warms $2\ \text{kg}$ of water by $10\ ^\circ\text{C}$? ($c = 4200\ \tfrac{\text{J}}{\text{kg}\cdot^\circ\text{C}}$.) Answer in $\text{J}$. · 使 $2\ \text{kg}$ 的水升温 $10\ ^\circ\text{C}$ 需要多少热量？($c = 4200\ \tfrac{\text{J}}{\text{kg}\cdot^\circ\text{C}}$.) 答案单位为 $\text{J}$。
$Q = mc\Delta T = 2 \times 4200 \times 10 = 84\,000\ \text{J}$.
The heat needed to warm a mass is $Q = m c \_\_$ (fill in the missing symbol). · 加热一定质量所需的热量为 $Q = m c \_\_$（填入缺失的符号）。
$Q = mc\Delta T$ — mass times specific heat times temperature change. · $Q = mc\Delta T$ —— 质量乘以比热容乘以温度变化。
Why water is special
- Water has an unusually high specific heat, so it stores lots of heat with little temperature change.
- This is why the sea warms and cools slowly, moderating coastal climates.
- It is also why water is used as a coolant in engines and power plants.
- Metals, with low $c$, respond to heat quickly — good for cooking pans.
水为何特殊
- 水有异常高的比热容,所以它储存大量热却温度变化很小。
- 这就是为什么海水加热和冷却都很慢,调节着沿海气候。
- 这也是水在引擎和电厂中被用作冷却剂的原因。
- 金属 $c$ 低,对热反应很快——适合做炒锅。
A material with a high · 高 specific heat capacity: · 具有高比热容的材料：
High $c$ (like water) means a lot of energy per degree, so slow temperature change. · 高 $c$（如水）意味着每度需要大量能量，因此温度变化缓慢。
Why is water often used as a coolant in engines? · 为什么水常被用作发动机冷却剂？
Water's high $c$ soaks up heat without getting very hot — ideal for carrying heat away. · 水的高 $c$ 使其能吸收热量而不会变得很热——非常适合带走热量。
Select all · 所有 true statements. · 选择所有正确的陈述。
The first three are true. The last describes conductivity, not specific heat. · 前三项是正确的。最后一项描述的是热导率，而非比热容。
Thermal conductivity
- Thermal conductivity measures how fast heat flows through a material.
- Metals conduct heat quickly (they feel cold because they draw heat from your hand).
- Insulators like wood, foam and air conduct slowly, trapping heat.
- Conductivity is about the speed of heat flow; specific heat is about how much heat to warm up.
热导率
- 热导率量度热穿过一种材料的快慢。
- 金属传热很快(它们摸起来凉,是因为把热从你手里抽走)。
- 木头、泡沫和空气这类绝缘体传得慢,把热困住。
- 热导率关乎热流的速度;比热容关乎变暖需要多少热。
Specific heat and thermal conductivity are the same property. · 比热容和热导率是相同的属性。
Specific heat is energy per degree; conductivity is how fast heat flows through — different ideas. · 比热容是每度的能量；热导率是热量通过材料的流速——这是不同的概念。
Don't confuse specific heat with thermal conductivity. Specific heat ($c$) is how much energy a material needs to change its temperature; conductivity is how fast heat passes through it. Water has a high specific heat but is a poor conductor.
不要把比热容和热导率弄混。比热容($c$)是一种材料改变温度需要多少能量;热导率是热穿过它的快慢。水比热容高,却是不良的导体。
How much heat warms $2\ \text{kg}$ of water by $10\ ^\circ\text{C}$? (Take $c = 4200\ \tfrac{\text{J}}{\text{kg}\cdot^\circ\text{C}}$.)
- $Q = mc\Delta T = 2 \times 4200 \times 10 = 84\,000\ \text{J}$.
The same heat would warm a metal of much lower $c$ far more than $10\ ^\circ\text{C}$.
把 $2\ \text{kg}$ 的水加热 $10\ ^\circ\text{C}$ 需要多少热?(取 $c = 4200\ \tfrac{\text{J}}{\text{kg}\cdot^\circ\text{C}}$。)
- $Q = mc\Delta T = 2 \times 4200 \times 10 = 84\,000\ \text{J}$。
同样的热会把 $c$ 低得多的金属加热远超 $10\ ^\circ\text{C}$。
Specific heat capacity $c$ is the heat per kilogram per degree: $Q = mc\Delta T$. A high $c$ (water) resists temperature change; a low $c$ (metal) heats up fast. Thermal conductivity is a different property — how fast heat flows through a material.
比热容 $c$ 是每千克每度所需的热:$Q = mc\Delta T$。高 $c$(水)抵抗温度变化;低 $c$(金属)加热得快。热导率是另一个性质——热穿过一种材料的快慢。