Certified Fire Investigator Practice Exam

How is "Gas" defined in terms of its physical properties?

1. A state of matter that has a definite volume and shape

2. A state of matter with no shape or volume of its own

3. A state of matter that can condense into a liquid

4. A state of matter that has high density

The correct answer is: A state of matter with no shape or volume of its own

Gas is defined as a state of matter that has no definite shape or volume of its own. In this state, the particles are widely spaced and move freely, causing the gas to expand and fill any available space. Unlike solids, which have fixed shapes and volumes, and liquids, which have fixed volumes but take the shape of their container, gases do not retain a specific form or size. This ability to expand and fill their containers is one of the key characteristics that differentiate gases from solids and liquids. The other descriptions do not accurately capture the fundamental nature of gases. For instance, the definition of a state of matter that has a definite volume and shape pertains to solids, not gases. The statement regarding the ability to condense into a liquid highlights a property of certain gases under specific conditions, but it does not represent the definition of gas itself. Lastly, while many gases can be less dense than solids and liquids, referring to high density does not accurately describe gases, which often have lower densities compared to other states of matter.