03.2 - Modeling a Gas

Understandings:

• Pressure

• Equation of state for an ideal gas

• Kinetic model of an ideal gas

• Mole, molar mass and the Avogadro constant

• Differences between real and ideal gases

Applications and skills:

• Solving problems using the equation of state for an ideal gas and gas laws

• Sketching and interpreting changes of state of an ideal gas on pressure–volume, pressure–temperature and volume–temperature diagrams

• Investigating at least one gas law experimentally

Guidance:

• Students should be aware of the assumptions that underpin the molecular kinetic theory of ideal gases

• Gas laws are limited to constant volume, constant temperature, constant pressure and the ideal gas law

• Students should understand that a real gas approximates to an ideal gas at conditions of low pressure, moderate temperature and low density

Data booklet reference:

Theory of knowledge:

• When does modelling of “ideal” situations become “good enough” to count as knowledge?

Utilization:

• Transport of gases in liquid form or at high pressures/densities is common practice across the globe. Behaviour of real gases under extreme conditions needs to be carefully considered in these situations.

• Consideration of thermodynamic processes is essential to many areas of chemistry (see Chemistry sub-topic 1.3)

• Respiration processes (see Biology sub-topic D.6)

Aims:

• Aim 3: this is a good topic to make comparisons between empirical and theoretical thinking in science

• Aim 6: experiments could include (but are not limited to): verification of gas laws; calculation of the Avogadro constant; virtual investigation of gas law parameters not possible within a school laboratory setting