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.

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.