Question

Examine the following processes.

i. Glucose breaks down in our bodies to provide energy.
ii. A lump of sugar dissolves in a cup of coffee.
iii. A candle burns.
iv. Ice cream melts on a hot day.
v. Food is refrigerated in a refrigerator.
vi. A drop of food coloring spreads in a glass of water.

Which arrangement correctly categorizes the above processes into either spontaneous or nonspontaneous processes?
spontaneous: i
nonspontaneous: ii, iii, iv, v, vi
spontaneous: i, ii, v
nonspontaneous: iii, iv, vi
spontaneous: i, ii, iii, iv, vi
nonspontaneous: v
spontaneous: i, v
nonspontaneous: ii, iii, iv, vi

Answer 1

Correct choice: spontaneous: i, ii, iii, iv, vi; nonspontaneous: v.

Brief justification:
- i (glucose breakdown): overall exergonic (ΔG < 0) under physiological conditions — spontaneous.
- ii (sugar dissolving): dissolution in hot coffee increases entropy and is spontaneous.
- iii (candle burning): combustion is thermodynamically spontaneous (ΔG < 0); it requires an activation step (ignition) but is still a spontaneous process.
- iv (ice cream melting on a hot day): melting above the melting point is spontaneous.
- v (food refrigerated): moving heat from cold interior to warmer surroundings requires work (nonspontaneous).
- vi (food coloring spreading): diffusion increases entropy and occurs spontaneously.