Thermal Expansion Differences

Steps:

• Identify materials: Jar is glass (low expansion), lid is metal (high expansion).
• Recall thermal expansion: Heating causes materials to expand, with metals expanding more than glass.
• Apply to lid removal: Expanding the lid loosens its fit on the jar.
• Evaluate options: Only heating the lid achieves differential expansion without affecting the jar.

Why D is correct:

• Heating the metal lid causes greater expansion than the glass jar (coefficient of thermal expansion for metals ~20-25 × 10⁻⁶/°C vs. glass ~9 × 10⁻⁶/°C), loosening the seal per linear expansion formula ΔL = α L ΔT.

Why the others are wrong:

• A: Cooling the lid contracts it, tightening the fit on the jar.
• B: Cooling both contracts them equally, maintaining the tight seal.
• C: Heating the jar expands it more than the lid, tightening the fit.

Final answer: D