Air is mainly composed of nitrogen, oxygen, and argon, which together constitute the major gases of the atmosphere. Water vapor accounts for roughly 0.25% of the atmosphere by mass.
Physical property, such as real estate, does not qualify due to the unpredictable length of the sales process. As retirement accounts, 401(k)s and IRAs operate both as liquid assets and non-liquid assets depending on the circumstance.
Companies often divide their assets into net liquid, quick, and current assets. Net liquid assets are what would be left if all of the businesses debts were paid off. Quick assets are those that can be converted into cash immediately, while current assets are those that can be converted within a year.