Identify the device shown, label its parts I-VI, explain the function of parts I, II, IV, and VI, and state one use of the device.

b)

i) The device shown by the diagram is a thermos flask (or vacuum flask).

ii) The parts labelled I to VI are:

• I: Stopper (or Cork)
• II: Outer casing (or Outer wall)
• III: Vacuum
• IV: Spring support
• V: Silvered surface (or Reflective coating)
• VI: Inner wall (or Glass bottle)

iii) One function of each of the parts labelled I, II, IV, and VI:

• I (Stopper): Prevents heat loss or gain by convection and conduction through the opening.
• II (Outer casing): Provides structural support and protection for the inner glass bottle.
• IV (Spring support): Holds the inner glass bottle in place and absorbs shocks to prevent breakage.
• VI (Inner wall): Contains the liquid and, with its silvered surface, reduces heat transfer by radiation.

iv) One use of the household device is to keep liquids hot or cold for an extended period.