Standard 5c Preknowledge
5c) Students know how to apply the gas laws to relations between the pressure, temperature, and volume of any amount of an ideal gas or any mixture of ideal gases.
CALIFORNIA FRAMEWORKS SUMMARY: A fixed number of moles n of gas can have different values for pressure P, volume V, and temperature T. Relationships among these properties are defined for an ideal gas and can be used to predict the effects of changing one or more of these properties and solving for unknown quantities. Students should know and be able to use the three gas law relationships summarized in Table 1, “Gas Law Relationships.”
Table 1
Gas Law Relationships
| Expression of gas laws |
Fixed values |
Variable relationships |
Form for calculations |
| PV = constant | n, T |
Inverse | P1V1 = P2V2 |
| V/T = constant | n, P |
Direct | V1/T1 = V2/T2 |
| P/T = constant | n, V |
Direct | P1/T1 = P2/T2 |
The first expression of the gas law shown in Table 1 is sometimes taught as Boyle’s law and the second as Charles’s law, according to the historical order of their discovery. They are both simpler cases of the more general ideal gas law introduced in Standard 4.h in this section. For a fixed number of moles of gas, a combined gas law has the form PV/T = constant, or P1V1/T1 = P2V2/T2. This law is useful in calculations where P, V, and T are changing. By placing a balloon over the mouth of an Erlenmeyer flask, the teacher can demonstrate that volume divided by temperature equals a constant. When the flask is heated, the balloon inflates; when the flask is cooled, the balloon deflates.