能量不会凭空产生或消失
Energy can't be created or destroyed
解释能量守恒定律（能量既不会凭空产生，也不会凭空消失，只会在不同的能量储存形式之间转移），并说明在一切真实过程中，能量都会以热能的形式耗散到周围环境中。
Explain the principle of conservation of energy (energy cannot be created or destroyed, only transferred between stores), and describe how energy is dissipated as thermal energy to the surroundings in all real processes
学习证据 / Evidence
- 说出能量守恒定律
- 解释为什么在封闭系统中，总能量即使发生变化形式，也始终保持不变
- 解释耗散是什么意思，以及为什么真实机器中会出现耗散（如摩擦、空气阻力）
- 举例说明为什么被“浪费”的能量并没有消失，而是转移到了周围环境中
- States the law of conservation of energy
- Explains why the total energy in a closed system is always the same even though it changes form
- Explains what dissipation means and why it happens in real machines (friction, air resistance)
- Gives an example showing why 'wasted' energy is not lost but transferred to the surroundings
评估问题 / Assessment
如果{{name}}给手机充电一整晚，有人问电能去了哪里，{{name}}能不能解释能量守恒是什么意思，并说明为什么充电器会发热，即使这些热量并没有做任何有用功？
If {{name}} charged their phone overnight and was asked where the electrical energy goes, could they explain what conservation of energy means — and why the charger gets warm even though that heat isn’t doing any useful work?