International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What is the physical state of nitrogen gas, N₂, at room temperature?

1. Solid

2. Liquid

3. Gas

4. Plasma

The correct answer is: Gas

Nitrogen gas, represented as N₂, is present in the atmosphere as a diatomic gas and constitutes about 78% of the Earth's atmosphere by volume. At room temperature, which is typically around 20-25 degrees Celsius, nitrogen remains in a gaseous state. This behavior is due to the weak intermolecular forces present between nitrogen molecules, which cannot hold them together in a denser form like a solid or liquid under these conditions. In contrast, solid and liquid states require stronger intermolecular forces to keep the molecules close together. Similarly, plasma refers to a state of matter where the gas phase is energized until atomic electrons are no longer associated with the nucleus, which is not applicable to nitrogen at room temperature. Thus, gas is the appropriate physical state for nitrogen at standard conditions.