Understanding Materials Used in Plastics Production

Plastics are a vast range of synthetic or semi-synthetic organic compounds that are malleable and can be molded into solid objects. They are typically organic polymers of high molecular mass, and often contain other substances. The building blocks of these polymers are smaller molecules called monomers.

Which Substance is Used in Plastics? Analyzing the Options

Let's examine the given options to determine which one is commonly used in the production of plastics.

• Krypton: Krypton ($\text{Kr}$) is a chemical element, a noble gas. Noble gases are known for being very unreactive due to their stable electron configuration. They are not used as monomers or primary components in the production of common plastics.
• Ammonia: Ammonia ($\text{NH}_3$) is a compound of nitrogen and hydrogen. It is a key substance in the chemical industry, used in fertilizers, cleaning products, and the production of other chemicals. However, it is not a monomer used to form the long polymer chains that make up typical plastics like polyethylene or polypropylene.
• Butane: Butane ($\text{C}_4\text{H}_{10}$) is a simple hydrocarbon, an alkane. It is a saturated molecule, meaning it has only single bonds between carbon atoms. While hydrocarbons are the source of many monomers (often through cracking or other processes), butane itself is not a primary monomer for common addition polymers like polyethylene. It is often used as a fuel or propellant.
• Ethylene: Ethylene ($\text{C}_2\text{H}_4$) is also a simple hydrocarbon, but it is an alkene, containing a carbon-carbon double bond. This double bond is highly reactive and allows ethylene molecules to link together repeatedly in a process called polymerization. This process forms very long chains of repeating ethylene units, creating the polymer known as polyethylene.

Ethylene: A Key Monomer for Polyethylene

Ethylene is one of the most important monomers in the plastics industry. Through a process called addition polymerization, thousands or even millions of ethylene molecules add onto each other to form long polymer chains. The chemical reaction can be simply represented as:

\(\text{n C}_2\text{H}_4 \rightarrow \text{ (C}_2\text{H}_4\text{)}_n\)

Here, \(\text{n}\) represents a large number of repeating units. The resulting polymer, polyethylene, is a widely used plastic found in everything from packaging films and bags to bottles, pipes, and containers.

Conclusion

Based on the properties and uses of the substances listed, Ethylene is the compound that is directly used as a monomer to produce one of the most common types of plastic, polyethylene.

Revision Table: Key Concepts in Plastic Production

Additional Information: Types of Plastics and Monomers

Plastics are incredibly diverse, and they are made from many different types of monomers. For example:

• Vinyl chloride monomer forms polyvinyl chloride (PVC).
• Propylene monomer forms polypropylene (PP).
• Styrene monomer forms polystyrene (PS).
• Ethylene glycol and terephthalic acid monomers form polyethylene terephthalate (PET).

Each type of monomer and the resulting polymer gives the plastic different properties, making them suitable for various applications.