Plastics are polymers that can be molded when heated. Which of the following is a thermosetting plastic?
A. Polyethylene
B. Bakelite
C. Nylon
D. PVC
Answer: Option B
Solution (By JKExamLibrary)
Bakelite is a thermosetting plastic (phenol-formaldehyde resin). Once set, it cannot be remolded by heating because its polymer chains are cross-linked. Polyethylene, PVC, and nylon are thermoplastics—they can be repeatedly softened by heat and hardened on cooling. Thermosetting plastics are used for electrical switches, handles, and adhesives. Vulcanized rubber is also thermoset.
Explanation:
Natural gas is predominantly methane (CH₄), typically 70-95%. Ethane, propane, butane are minor components. CNG is compressed natural gas.
Explanation:
Bronze is an alloy primarily of copper and tin, sometimes with other elements. Brass is Cu-Zn. Steel is Fe-C. Duralumin is Al-Cu-Mg-Mn. Bronze is used for statues, coins, and bearings.
Explanation:
Amphoteric oxides react with both acids and bases to form salts and water. Aluminum oxide (Al₂O₃) and Zinc oxide (ZnO) are classic examples. Na₂O and MgO are basic oxides that react only with acids, while SO₂ is an acidic oxide that reacts only with bases.
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