The short answer
The ideal gas law PV = nRT and the relationships behind it — with the Kelvin trap.
Written and checked by GAMSAT tutors — not AI-generated.
Try the reasoning style
We treat forgetting as a failure — a lapse to be patched with reminders and records. Yet a mind that kept everything could not think; it would drown in the undifferentiated noise of every moment it had ever lived. To forget is not so much to lose information as to decide, mostly without our noticing, what was never worth keeping.
The author's argument relies most directly on which unstated assumption?
Pick an option to see how the tutor reasons to the answer — not just whether you were right.
Not quite — the answer is B.
Work backwards from the conclusion: a mind that ‘kept everything’ supposedly ‘could not think.’ That only follows if thinking means leaving most of experience out — so B is the premise the argument quietly rests on. A raises reliability, which the passage never weighs; C contradicts ‘mostly without our noticing’; D smuggles in a claim about intellect the passage never makes. The question rewards finding the hidden premise, not recalling a fact.
Gases are wonderfully predictable: squeeze one and its pressure rises; heat it and it expands. The ideal gas law, , captures all of it, and the simpler gas laws are just special cases where you hold one variable fixed.
One master equation
— pressure × volume = moles × gas constant × temperature. The individual laws follow by holding things constant: Boyle's ( at fixed T), Charles' ( at fixed P), Gay-Lussac's ( at fixed V).
Always use Kelvin
Temperature in gas-law calculations must be in Kelvin (). Using Celsius gives nonsense — for example, "doubling" from 1 °C to 2 °C is almost no change in absolute terms, but 274 K to 548 K is a real doubling. This is the single most common gas-law mistake.
The simple gas laws (fix one variable)
Boyle's law (constant T)
- Squeeze the volume → pressure rises
Charles' law (constant P)
- Heat the gas → it expands
- (T in Kelvin)
Worked example
A gas occupies 6 L at a pressure of 2 atm. If the temperature is constant and the pressure is increased to 3 atm, what is the new volume?
Check yourself
At constant pressure, the absolute (Kelvin) temperature of a fixed amount of gas is doubled. What happens to its volume?
Key takeaways
- Ideal gas law: .
- Boyle's: (constant T). Charles': (constant P).
- Always convert temperature to Kelvin (K = °C + 273).
- Squeezing volume raises pressure; heating raises volume (or pressure).
- The simple laws are just PV = nRT with one variable held fixed.
Practise this with real GAMSAT-style questions
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