Question

Predict the sign for AS for each of the following systems: Water freezing Water evaporating Crystalline urea dissolving Assembly of the plasma membrane from individual lipids. Assembly of a protein from individual amino acids.

Answer 1

Answer: 1. Water freezing :
`\Delta S` is -ve.

2. Water evaporating :
`\Delta S` is +ve.

3. Crystalline urea dissolving :
`\Delta S` is +ve.

4. Assembly of the plasma membrane from individual lipids:
`\Delta S` is -ve.

5. Assembly of a protein from individual amino acids:
`\Delta S` is -ve.

Step-by-step explanation:

Entropy is defined as the measurement of degree of randomness in a system.

It is represented by symbol S and we can only measure a change in entropy which is given by
`\Delta S`.

If there is decrease in randomness , the sign for
`\Delta S` is -ve and If there is increase in randomness , the sign for
`\Delta S` is +ve.

1. Water freezing: Entropy decreases as we move from liquid state to to solid state and thus
`\Delta S` is -ve.

2. Water evaporating : Entropy increases as we move from liquid state to gaseous state and thus
`\Delta S` is +ve.

3. Crystalline urea dissolving : The molecules convert from solid and ordered state to aqueous phase and random state. Thus the entropy increases and thus
`\Delta S` is +ve.

4. Assembly of the plasma membrane from individual lipids: random lipids are associating to form a single large polymer and thus entropy decreases and thus
`\Delta S` is -ve.

5. Assembly of a protein from individual amino acids: random amino acids are associating to form a single large polymer and thus entropy decreases and thus
`\Delta S` is -ve.