What do you mean by degradation of energy? Explain it by taking two examples of your daily life.

Assertion (A) : Fishes survive in ponds even when the atmospheric temperature is below 0°C.

Reason (R) : The anomalous expansion of water helps in preserving aquatic life.

1. both A and R are true and R is the correct explanation of A
2. both A and R are true and R is not the correct explanation of A
3. assertion is false but reason is true
4. assertion is true but reason is false

A scientific research team records temperature data of a freshwater lake in the Himalayas during winter. Three thermometers A, B, and C are used, where A is calibrated in the Celsius scale, B in the Fahrenheit scale, and C in the Kelvin scale.

On a particular night, when the surface water of the lake freezes, the recorded temperatures are :

A ⟶ 0 °C, B ⟶ 32 °F, C ⟶ 273 K

Next morning, the air temperature increases slightly, but the ice on the surface of the lake does not melt immediately.

(a) What happens to the fish present in the lake when the surface of the lake freezes?

(b) If the temperature of water at the bottom of the lake is measured, what would be the readings on thermometers A, B, and C?

(c) Why does the ice formed on the surface of the lake not sink?

(d) Why does the ice on the lake take time to melt even after the air temperature rises above 0 °C?

(e) Why is the Kelvin scale preferred in scientific calculations related to heat transfer?

Two cities, P and Q, have identical population and climate. City P uses coal-based thermal power and diesel vehicles, whereas City Q uses solar and wind energy along with electric vehicles.

(a) Which city is likely to show a higher average temperature rise after 10 years?

(b) Identify the main greenhouse gases responsible for the higher temperature rise in the city mentioned above by you in (a).

(c) "Energy is conserved, so using fossil fuels or renewable sources makes no difference."

Is this statement scientifically correct? Give reason.

(d) Give physics-based reasons to explain which city will have long-term energy sustainability.