Question

Choose the system from each pair that likely has the higher entropy.

ice
liquid water

liquid water at 10°C
liquid water at 90°C

1 mol NaBr dissolved in 1 L water

1 mol solid NaBr and 1 L pure water in separate containers

Answer 1

1) Liquid water — melting increases molecular freedom and disorder (more accessible microstates) so liquid has higher entropy than ice.

2) Liquid water at 90°C — at higher temperature the molecules have more accessible energy microstates; S increases with T, so 90°C water has higher entropy than 10°C water.

3) 1 mol NaBr dissolved in 1 L water — dissolution and mixing disperse the ions and increase configurational freedom (mixing/solvation entropy), so the solution has higher entropy than the same salt as a separate solid plus pure water.