Victory for the ACT Student Text 15e

312 • S CIENCE

PASSAGE IV

states that the volume, V

, of a gas at constant pressure is proportional to its

Charles’s law absolute temperature T V T ?

(temperature in kelvins, K):

(Equation 1)

Throwback to Science Remember what it means for two variables to be proportional. As one variable goes up, the other goes up as well. Similarly, when two variables are inversely proportional, when one variable goes up, the other goes down. It can be helpful to draw arrows so that you can easily and quickly remember this concept while testing. For example: For Šƒ”Ž‡•ǯ• Žƒ™ǡ ՛ V ƒ† ՛ T , and for ‘›Ž‡ǯ• Žƒ™ǡ ՛ V and ՝ P .

Boyle’s law states that the volume of a gas at constant temperature is inversely proportional to its pressure P : / V P 1 ? (Equation 2) Experiment 1 Students inserted a 100-mL syringe and a thermometer through holes in a rubber stopper ƒ† ’Žƒ…‡† –Š‡ •–‘’’‡” ‹–‘ ƒ ϐŽƒ• –Šƒ– Šƒ† „‡‡…‘‘Ž‡† ‹ ƒ ‹…‡ „ƒ–Š –‘ ʹ͹͵ ȋ ‹‰—”‡ ͳȌǤ Š‡› –Š‡ ”‡‘˜‡† –Š‡ ϐŽƒ• ˆ”‘ –Š‡ ‹…‡ „ƒ–Š ƒ† ’Žƒ…‡† ‹– ‘ ƒ Š‘– ’Žƒ–‡Ǥ Š‡ ‰ƒ• ‹ –Š‡ ϐŽƒ• ‡š’ƒ†‡† ƒ• ‹– ™ƒ”‡†ǡ •Ž‘™Ž› ’—•Š‹‰ –Š‡ ’‹•–‘ —’ –Š‡ •›”‹‰‡Ǥ –—†‡–• ”‡…‘”†‡† –Š‡ temperature and corresponding syringe volume readings as the gas expanded at a constant atmospheric pressure (100 kPa). To obtain the total volume of the gas in the system, they ƒ††‡† –Š‡ ˜‘Ž—‡ ‘ˆ –Š‡ •›”‹‰‡ –‘ –Š‡ ˜‘Ž—‡ ‘ˆ –Š‡ ϐŽƒ•Ǥ Š‡ •–—†‡–•…”‡ƒ–‡† ƒ ‰”ƒ’Š ‘ˆ –Š‡ experimental data (Figure 2).

Figure 1

Figure 2