Problem 90 - Chemistry: The Central Science

Question

Indicate whether each statement is true or false: (a) Elastomers are rubbery solids. (b) Thermosets cannot be reshaped. (c) Thermoplastic polymers can be recycled.

Step-by-Step Solution

Answer

(a) True: Elastomers are rubbery solids due to their high flexibility and low glass transition temperature. (b) True: Thermosets cannot be reshaped, as they undergo irreversible chemical reactions when formed. (c) True: Thermoplastic polymers can be recycled, as they can be melted and reshaped multiple times without significant change in molecular structure.

Step 1: Statement (a) Elastomers are rubbery solids.

Elastomers are a type of polymer with unique characteristics, including high flexibility and a low glass transition temperature. This allows them to be stretched easily without breaking and return to their original shape after releasing the stress. Due to their properties, elastomers indeed behave as rubbery solids. Therefore, statement (a) is true.

Step 2: Statement (b) Thermosets cannot be reshaped.

Thermosets are polymers that undergo irreversible chemical reactions when they are formed. Unlike thermoplastic polymers, which can be melted and reshaped multiple times, thermosets undergo a permanent change in their molecular structure when they are cured or set. As a result, once they have been shaped and cured, thermosets cannot be reshaped or reprocessed without damaging their structure. Therefore, statement (b) is true.

Step 3: Statement (c) Thermoplastic polymers can be recycled.

Thermoplastic polymers are polymers that can be melted and reshaped multiple times without undergoing a significant change in their molecular structure. This property makes them suitable for recycling, as they can be melted and processed into new products without degrading their performance. Thus, statement (c) is true. In summary, all three statements provided in the exercise are true.