A chef balances two identical 25 cm × 5 cm × 1 cm slabs across the rims of two pots…
CHEMISTRY · Single correct · A Level · Chemistry · Bonding · Bonding
Problem
A chef balances two identical 25 cm × 5 cm × 1 cm slabs across the rims of two pots and then presses downward at the center of each slab with the same force. One slab is aluminum, the other is compressed table salt (NaCl). The salt slab cracks while the aluminum slab merely bends. Which statement most directly accounts for this observation?
(a) NaCl possesses a much larger lattice energy than aluminum, so its ionic lattice cannot deform under stress and instead cracks, while aluminum’s lower lattice energy permits the lattice to flex.
(b) The mobile sea of electrons in aluminum rapidly redistributes the applied force throughout the slab, but NaCl lacks mobile charge carriers so the stress remains localized and the crystal breaks.
(c) Aluminum atoms are held together by nondirectional metallic bonding that allows atomic layers to slide without breaking, whereas sliding layers in NaCl brings like charges next to each other, causing repulsion and fracture.
(d) Because aluminum has a lower density (and molar mass) than NaCl, the same downward force produces less stress on each aluminum atom, so the metal bends rather than fractures.