Which of the following is commonly used as a lubricant?

Lubricants are substances used to reduce friction and wear between moving surfaces. They are essential in machines, engines, and industrial equipment to improve efficiency and prevent damage. Among the given options, graphite is the most commonly used lubricant.

Graphite is a form of carbon with a layered structure. Its carbon atoms are arranged in hexagonal sheets, where each layer is held together weakly by van der Waals forces. This allows the layers to slide easily over each other, giving graphite its slippery texture. Because of this property, graphite is used as a dry lubricant in applications where oil or grease cannot be used, such as locks, bearings, and high-temperature machinery.

Other options are less suitable as lubricants:

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  Silica is a hard, abrasive substance commonly used in glass and ceramics, not as a lubricant.

  
  


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  Diamond is extremely hard and rigid; it does not slide easily and cannot function as a lubricant.

  
  


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  Iron oxide is a corrosion product, abrasive, and is also unsuitable for reducing friction.

  
  

Graphite’s ability to resist high temperatures, chemical inertness, and stability makes it ideal for both industrial and everyday applications. Additionally, it can be combined with oils to form lubricating greases or used in pencil “lead” where it also demonstrates sliding properties.

Understanding the use of graphite as a lubricant is important in Chemistry and everyday science, as it illustrates how atomic structure and bonding determine physical properties and practical applications. This knowledge connects theory with real-world applications in machines, manufacturing, and materials science, showing how fundamental chemistry impacts everyday life.