Glass is generally considered better for boiling water compared to ceramic. This is primarily due to its lower thermal expansion coefficient, which means it is less likely to crack or break when exposed to rapid temperature changes. Additionally, glass is non-porous, making it easier to clean and less prone to bacterial growth. Ceramic, while also durable, can absorb moisture and potentially harbor bacteria, which may affect the purity of the water.

Glass is made from silica, a material with a very low thermal expansion coefficient, which means it can withstand temperature changes without cracking. This property makes it ideal for boiling water, as the glass pot can handle the heat without warping or shattering. On the other hand, ceramic is made from clay and other minerals, which have a higher thermal expansion coefficient. This can make ceramic pots more susceptible to cracking or chipping when exposed to sudden temperature changes, such as when boiling water.

According to a study published in the Journal of Materials Science: Materials in Medicine, the thermal expansion coefficient of glass is typically around 3.3 x 10^-5 per degree Celsius, while ceramic can range from 5.0 x 10^-5 to 9.0 x 10^-5 per degree Celsius. This difference in thermal expansion can lead to durability issues with ceramic pots over time, especially when used for boiling water.

Furthermore, glass is non-porous, which means it does not absorb water or other substances. This makes it easier to clean and less likely to harbor bacteria or other contaminants. Ceramic, on the other hand, can absorb moisture, which can lead to the growth of bacteria and other microorganisms. A study published in the Journal of Applied Microbiology found that ceramic surfaces can harbor more bacteria than glass surfaces, which can be a concern for water purity.

In conclusion, glass is the better choice for boiling water due to its lower thermal expansion coefficient, non-porous nature, and overall durability. These factors make glass pots more resistant to cracking, easier to clean, and less likely to harbor bacteria, ensuring the purity of the water being boiled.