When conc. $\mathrm{H}_2\mathrm{SO}_4$ is poured on the cane sugar, acid acts as dehydrating agent which removes moisture from sugar and sugar turns into spongy mass of carbon called sugar charcoal.When conc. $\mathrm{H}_2\mathrm{SO}_4$ is added to $\mathrm{CuSO}_4$ . $5\mathrm{H}_2\mathrm{O}$ , acid acts as dehydrating agent, which removes crystalline water. The salt converted into anhydrous salt which has white. $\; \underset{\; \text{" Blue "} \;}{\mathrm{CuSO}_4\cdot5\mathrm{H}_2\mathrm{O}} \xrightarrow[\mathrm{H}_2\mathrm{SO}_4]{\text{conc. }} \underset{\; \text{" White. "} \;}{\mathrm{CuSO}_4} + 5\mathrm{H}_2\mathrm{O}$