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Temperature effect on weight and density

Aviation Mechanic General (AMG) practice question 11 of 20 on Physics for Aviation. ACS element AM.I.J.K11 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA sample of hydraulic fluid is warmed and its volume expands. What happens to the weight and the density of the sample?

  1. ABoth weight and density remain unchanged
  2. BWeight decreases; density decreases
  3. CWeight is unchanged; density decreases
Show the answer and explanation

Correct answer: C. Weight is unchanged; density decreases

  • A — incorrect Weight stays the same, but because the volume grows, the weight per unit volume, which is density, must fall.
  • B — incorrect Heating does not remove any matter, so the weight of the sample is unchanged. Only the density changes.
  • C — correct Changes in temperature do not change the weight of a substance, but they change its volume by expansion. Since density is weight per unit volume, the same weight in a larger volume means lower density.

BACKGROUND

The density of a substance is its weight per unit volume, expressed in the English system as pounds per cubic foot. To find density, the weight is divided by the volume; water at 4 °C has a density of 62.4 lb/ft3 and is the standard for comparing liquids and solids. Changes in temperature will not change the weight of a substance, but they change its volume by expansion or contraction, which changes its weight per unit volume. For gases, pressure must also be considered, because the density of a gas increases in direct proportion to the pressure exerted on it.

STUDY TIP

Think of density as a ratio: temperature moves the volume in the denominator while weight in the numerator stays fixed.

KEY POINTS

  • Density = weight ÷ volume (lb/ft3)
  • Temperature changes volume, not weight
  • Expansion lowers density; contraction raises it

SOURCES

  • FAA-H-8083-30B ch05 "Density"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.