Question

Polyethylene is a flexible plastic with many industrial uses. The synthesis of polyethylene is a radical reaction that follows the equation: $$ w \mathrm{CH}_2=\mathrm{CH}_2 \rightarrow\left(\mathrm{CH}_2 \mathrm{CH}_2\right)_2 $$ Polyethylene is a( \(\mathrm{a})\) : A. molecular solid. B. polymer. C. jonic solid. D. network solid.

Short answer

B. polymer

Step-by-step solution

Understand the Definition of Polyethylene

Polyethylene is a type of plastic, which is synthesized through a radical reaction involving ethylene (CH₂=CH₂) as given in the equation.

Identify the Result of the Reaction

The given reaction shows that multiple ethylene (CH₂=CH₂) units join together to form a larger molecule (CH₂-CH₂)_n, where 'n' indicates the number of repeating units.

Define the Term 'Polymer'

A polymer is a large molecule made up of repeating structural units (monomers) linked by covalent bonds. In this case, the repeating unit is CH₂-CH₂.

Evaluate the Options

Examine the provided choices and match them to the characteristics of polyethylene: A. Molecular solid - Typically small molecules held by weak forces; not applicable.B. Polymer - A large molecule made of repeating units; this matches the synthesis process.C. Ionic solid - Composed of ions; not applicable.D. Network solid - Extended network of covalent bonds without identifiable repeating units; not applicable.

Select the Correct Answer

Based on the definitions and the process, the correct answer is B. polymer.

Key concepts

radical reaction

A radical reaction is a type of chemical reaction where the molecules involved have unpaired electrons, making them highly reactive. In the synthesis of polyethylene, ethylene molecules (CH₂=CH₂) undergo a radical reaction. This process starts when a radical initiator, such as a peroxide, breaks down to form radicals. These radicals then react with ethylene molecules, creating new radicals in subsequent steps. As a result, the ethylene radicals combine to form a long chain, resulting in the polyethylene polymer. This type of reaction is central to making many types of plastics.

polymerization process

The polymerization process is the method of forming a polymer from simpler building blocks, or monomers. In the case of polyethylene, polymerization involves multiple ethylene (CH₂=CH₂) units linking together. This happens through a series of radical reactions, known as chain-growth polymerization. As each radical reacts with an ethylene molecule, it adds to the chain, forming a longer polymer. This process continues until the radicals get neutralized or terminated. The result is a large, flexible molecule known as polyethylene, which has various industrial applications due to its strength and flexibility.

chemical properties of polymers

Polymers like polyethylene have unique chemical properties making them very useful in many applications. These properties depend on the repeating units and the way they’re linked. For example, polyethylene is made up of repeating CH₂-CH₂ units, resulting in high ductility and flexibility. This makes it ideal for products like plastic bags and bottles. Polymers are generally large molecules, often referred to as macromolecules, which give them high melting points and the ability to form strong, durable materials. Additionally, they are resistant to chemicals and water, enhancing their functionality in various environments.

types of solids

Solids can be categorized based on the nature of their bonding and structure. The main types include:

• Molecular solids: Composed of small molecules held together by weak forces, such as van der Waals forces. Examples include ice and sugar.
• Ionic solids: Made of ions held together by strong ionic bonds. Salt (NaCl) is a common example.
• Network solids: Have a continuous network of covalent bonds, like diamond or quartz.
• Polymers: Consist of long chains of repeating units. Polyethylene falls into this category. These are characterized by their flexibility and varying degrees of hardness, depending on the type of polymerization used.

Understanding these categories helps in identifying the materials and their properties, as seen with polyethylene in the context of it being a polymer.