《Heavy》是Linkin Park的歌曲，歌詞如下：
Heavy
Verse 1：
All these years I've been trying to hold on
Trying to keep my head above the clouds
But now I'm sinking in the deep end
Trying to swim against the current
Chorus：
This is heavy, I'm feeling heavy
Trying to keep my feet on solid ground
This is heavy, I'm feeling heavy
Trying to keep my head above it all
Verse 2：
I've been trying to find my way home
But every road leads to a dead end street
And now I'm lost, I'm feeling lost and alone
Trying to keep my feet on solid ground
Bridge：
It's a feeling that I've never known
But I know that I've got to get through it alone
So I'll keep on trying, keep on pushing on
Trying to keep my feet on solid ground
Chorus：
This is heavy, I'm feeling heavy
Trying to keep my feet on solid ground
This is heavy, I'm feeling heavy
Trying to keep my head above it all
Outro：
It's heavy, and it doesn't look like it's gonna lift off一隻電熱水壺正常工作時的功率為1500W，加滿一桶2L的水需要3min燒開。則這隻電熱水壺的熱效率是多少？燒開這桶水需要的電能是多少？這些熱量可以讓質量為多少的初溫為35℃的水升到沸騰所需的熱量？（已知水的比熱容為4.2 × 10^{3}J/(kg \cdot^{\circ}C)，電熱水壺正常工作時的熱效率為75％）
【分析】
知道電熱水壺正常工作時的功率和燒開水的質量，利用$P = \frac{W}{t}$求電熱水壺正常工作消耗的電能；再利用$Q_{吸} = cm\Delta t$求出吸收的熱量，根據熱效率公式求出燒開這桶水需要的電能；再利用$Q_{吸} = Q_{放}$求水的質量。本題考查了學生對吸熱公式$Q_{吸} = cm\Delta t$、熱效率公式、電功公式的掌握和運用，能利用控制變數法進行解釋現象是本題的關鍵。本題主要考查了熱效率公式、電功公式的靈活套用。
【解答】
解：（$1$）由$P = \frac{W}{t}$可得，電熱水壺正常工作消耗的電能：$W = Pt = 1500W \times 3 \times 60s = 2.7 \times 10^{4}J$；
（$2$）由題知，$Q_{吸} = Q_{放} = \frac{W}{75\%} = \frac{2.7 \times 10^{4}J}{75\%} = 3.6 \times 10^{4}J$，由$Q_{吸} = cm\Delta t$可得，水的質量：$m = \frac{Q_{吸}}{c(t - t_{0})}$$\mspace{2mu}^{\prime} = \frac{3.6 \times 10^{4}J}{4.2 \times 10^{3}J/(kg \cdot^{\circ}C) \times (100^{\circ}C - 35^{\circ}C)}$$\approx 1kg$。答：這隻電熱水壺的熱效率是$75\%$；燒開這桶水需要的電能是$3.6 \times 10^{4}J$；這些熱量可以讓質量為$1kg$初溫為$35^{\circ}C$的水升到沸騰所需的熱量。