During the six-step process, when crystals are seen on the glass rod, what should you do?

• A. Stop heating
• B. Continue heating
• C. Add more solid
• D. Cool rapidly

Answer: (A)

The key idea is controlling crystallization through temperature. In this process, heating dissolves the solute and cooling makes crystals form. When crystals are seen on the glass rod, it shows crystallisation is starting or has begun. Stopping the heating allows the solution to cool gradually and crystals to grow rather than being dissolved again. Continuing to heat would keep more solute in solution and delay or prevent proper crystal formation. Adding more solid would push toward more material in solution rather than allowing existing crystals to form. Cooling rapidly tends to produce many tiny crystals and poorer quality, whereas a gentle cool lets crystals grow larger.