The correct option is **B. Synthetic polymers can be engineered to have specific properties not found in natural polymers.** ### Detailed Explanation: **Understanding Synthetic vs. Natural Polymers:** 1. **Definition of Polymers:** - Polymers are large molecules made up of repeating structural units called monomers. They can be classified into two main categories: natural polymers (like proteins, cellulose, and rubber) and synthetic polymers (like nylon, polyester, and polyethylene). 2. **Synthetic Polymers:** - Synthetic polymers are man-made and are created through chemical processes. They can be designed and engineered to have specific characteristics, such as flexibility, strength, resistance to chemicals, and thermal stability. This engineering allows for a wide range of applications, from everyday items like plastic bags to specialized materials used in aerospace and medical devices. 3. **Engineering Specific Properties:** - One of the key advantages of synthetic polymers is that chemists can manipulate their molecular structure to achieve desired properties. For example: - **Nylon** can be engineered to be strong and durable, making it ideal for clothing and ropes. - **Polyethylene** can be produced in different densities (low-density and high-density) to create materials suitable for various uses, from plastic wraps to heavy-duty containers. - This level of customization is often not possible with natural polymers, which have fixed structures and properties determined by their biological origins. ### Why the Other Options Are Incorrect: **A. Synthetic polymers are always biodegradable.** - **Explanation:** This statement is incorrect because most synthetic polymers are not biodegradable. They are designed to be durable and resistant to degradation, which is why they persist in the environment for long periods. While there are some biodegradable synthetic polymers (like polylactic acid), the statement implies that all synthetic polymers share this characteristic, which is not true. **C. Synthetic polymers are derived directly from natural sources without modification.** - **Explanation:** This statement is misleading. Synthetic polymers are not derived directly from natural sources; rather, they are created through chemical processes that often involve the modification of natural materials or the use of entirely synthetic monomers. For example, synthetic rubber is made from petrochemicals, not directly from natural rubber. **D. Synthetic polymers have lower tensile strength than natural polymers.** - **Explanation:** This statement is also incorrect. Many synthetic polymers can be engineered to have higher tensile strength than natural polymers. For instance, synthetic fibers like Kevlar are known for their exceptional strength and are used in bulletproof vests, far exceeding the tensile strength of many natural fibers. ### Summary of Key Points: - **Synthetic polymers can be tailored for specific applications**, allowing for unique properties that natural polymers may not possess. - **Most synthetic polymers are not biodegradable**, contrasting with some natural polymers that can decompose. - **Synthetic polymers are not derived directly from natural sources**; they are often created through complex chemical processes. - **Synthetic polymers can exhibit higher tensile strength** than many natural polymers, making them suitable for demanding applications. This understanding of synthetic versus natural polymers is crucial for anyone studying chemistry, especially in fields related to materials science and environmental impact.