Final answer:
Glass thermometers must be handled carefully due to their susceptibility to breaking from thermal stress. Pyrex, with a low coefficient of linear expansion, is less prone to breaking under these conditions.
Step-by-step explanation:
Special Care for Glass Thermometers
Glass thermometers require special care because they can break easily due to thermal stress.
When a glass thermometer is subject to uneven temperatures, it experiences different expansion rates, leading to stress and potential breakage. This is particularly important when a thermometer is allowed to come into equilibrium with the air and then placed in a medium, like water, that is not in equilibrium with the air.
The thermometer reading will change as the temperature of the water affects the liquid inside the thermometer.
Pyrex®, a type of glass with a small coefficient of linear expansion, is less susceptible to breaking from thermal stress.
Its low expansion rate means it can handle rapid temperature changes better than other glass types. This quality makes Pyrex ideal for laboratory and cookware use, as it minimizes the risk of breakage when exposed to sudden temperature shifts.
Regarding thermal properties, glass and metals differ substantially. Metals typically have higher coefficients of thermal expansion compared to glass, which means they expand and contract more with temperature changes.
Consequently, in situations like a metal lid screwed on a glass jar, the lid (metal) would expand more than the jar (glass) when heated, potentially making it easier to unscrew. However, practical issues such as wet surfaces can affect grip and make the task difficult.
When handling hot substances or glassware, it is essential to use protective equipment such as gloves, goggles, or safety aprons. If glass breaks, it should only be cleaned up with a dustpan and broom, never with bare hands, to prevent injury.