According to the Ideal Gas Law, what happens to the pressure when the temperature is increased and the volume is held constant?

Question

Options

• AThe pressure does not change.
• BThe pressure initially increases and then decreases.
• CThe pressure increases.
• DThe pressure decreases.

• A
  11% (7)
• B
  6% (4)
• C
  80% (52)
• D
  3% (2)

Explanation

Option C is correct because the Ideal Gas Law (PV = nRT) shows that pressure and temperature are directly proportional when volume and the amount of gas are held constant - this relationship is also known as Gay-Lussac's Law. As temperature rises, gas molecules gain kinetic energy and collide with the container walls more frequently and forcefully, which increases pressure. Option A is wrong because pressure is directly dependent on temperature and does change. Option B is wrong because the relationship is linear and monotonic - pressure rises steadily with temperature and does not reverse. Option D is wrong because a decrease in pressure would result from a decrease in temperature, not an increase.

Memory tip: Think of a sealed aerosol can left in a hot car - the warning label exists because heating a fixed volume of gas raises its pressure, sometimes to dangerous levels. If heat goes up and volume stays fixed, pressure goes up with it.

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