Here's why:
* Temperature and Molecular Motion: Temperature is a measure of the average kinetic energy of molecules. Higher temperatures mean faster-moving molecules.
* Phases of Matter: The different phases of matter (solid, liquid, gas) are defined by the strength of the intermolecular forces between molecules and their movement.
* Normal Atmospheric Pressure: At normal atmospheric pressure, the pressure exerted by the atmosphere on the substance is relatively constant. This pressure plays a role in determining the boiling point of a liquid, but it doesn't determine the phase at a given temperature.
Example:
* Water: At normal atmospheric pressure, water exists as a solid (ice) below 0°C, a liquid (water) between 0°C and 100°C, and a gas (steam) above 100°C.
While pressure can affect the phase of a substance (for example, increasing pressure can cause a substance to liquefy at a higher temperature), at normal atmospheric pressure, temperature is the primary factor determining the phase of matter.
