Which type of glass is commonly used for making chemical laboratory apparatus such as beakers, flasks, and test tubes because of its resistance to heat and chemical attack?

Introduction / Context:
Laboratory glassware such as beakers, flasks, test tubes, and measuring cylinders must withstand heating, cooling, and contact with a variety of chemicals without breaking or reacting. Not all types of glass are suitable for this purpose. Understanding which glass is used in chemical apparatus helps explain why some kitchen glassware cannot be safely used over a flame, while laboratory glassware can. This question asks you to identify the type of glass commonly used for chemical apparatus.

Given Data / Assumptions:

• The options are potash glass, hard glass, Jena glass, and soda glass.
• Chemical apparatus must resist heat shock and chemical corrosion.
• We assume standard terminology where “hard glass” refers to borosilicate glass used in laboratories.
• Soda glass is the ordinary glass used in window panes and bottles.

Concept / Approach:
Hard glass is a type of borosilicate glass containing silica and boron compounds. It has a low coefficient of thermal expansion, which means it can withstand rapid temperature changes without cracking, and it is more resistant to chemical attack than ordinary soda-lime glass. This makes it ideal for laboratory apparatus that may be heated over a flame or come into contact with acids and alkalis. Potash glass and Jena glass are specialised glass types, while soda glass is soft glass used in everyday items like bottles and window panes, which cannot tolerate high thermal shock. Therefore, for typical school and college laboratories, hard glass (borosilicate glass) is used to make beakers and flasks.

Step-by-Step Solution:
Step 1: Consider the requirements of laboratory glassware. It must endure heating, cooling, and contact with chemicals without cracking or reacting. Step 2: Recall the common laboratory glass type. Borosilicate glass, often branded as Pyrex or similar names, is used for laboratory items and is referred to in textbooks as hard glass. Step 3: Evaluate soda glass. Soda-lime glass is cheaper and used for bottles and window panes but is not suitable for direct heating. Step 4: Recognise that potash glass and Jena glass are not the standard answer in basic courses for common chemical apparatus. Step 5: Select “Hard glass” as the correct type for beakers and flasks.

Verification / Alternative check:
Descriptions of laboratory equipment often mention that beakers, flasks, and test tubes are made from borosilicate or hard glass to resist thermal shock and chemical attack. Safety instructions warn against using ordinary soda glass on burners because it may crack or shatter. Potash glass (potassium glass) and Jena glass are mentioned less frequently at school level, whereas “hard glass” is the typical textbook term. This pattern confirms that hard glass is the type generally associated with chemical apparatus.

Why Other Options Are Wrong:
Option A (Potash glass): Contains potassium oxide; it has some specialised uses but is not the standard term given for general laboratory glassware in school texts. Option C (Jena glass): A type of heat-resistant glass developed in Jena, Germany, but not the common exam answer for typical beakers and flasks. Option D (Soda glass): Ordinary soft glass used for bottles and windows; it cannot withstand strong heating and rapid temperature changes like hard glass can.

Common Pitfalls:
Students sometimes choose soda glass because it is the most familiar type or because they see it used in everyday containers. Another source of confusion is the presence of several technical glass names; without recalling which is linked to labware, they may guess randomly. To avoid this, remember that hard glass (borosilicate glass) is used in laboratories, while soda-lime glass is used in everyday items and is not flame-proof.

Final Answer:
Chemical apparatus like beakers and flasks are commonly made from Hard glass (borosilicate glass).