Question

some thermal containers have layers of materials to keep drinks cold for as long as possible. which design would help keep ice frozen for the longest period?

a. inner core of steel, no air gap, outer layer of steel

b. inner core of glass, air gap, outer layer of glass

c. inner core of glass, no air gap, outer layer of plastic

d. inner core of steel, air gap, outer layer of glass

Explanation:

To keep ice frozen longest, the container should minimize heat transfer. Heat transfer occurs via conduction, convection, and radiation. Materials with low thermal conductivity (insulators) and air gaps (which reduce conduction/convection) are key.

• Option A: Steel is a good conductor, no air gap—poor insulation.
• Option B: Glass (moderate insulator), air gap (reduces conduction/convection), glass outer—air gap and insulating materials (glass is better insulator than steel) help minimize heat in.
• Option C: No air gap—conduction is higher, plastic is insulating but no air gap reduces effectiveness.
• Option D: Steel inner (good conductor) allows heat in easily.

So B’s design (glass inner, air gap, glass outer) minimizes heat transfer best.

Answer:

B. Inner core of glass, air gap, outer layer of glass