How Intermolecular Forces Affect Matter

Intermolecular forces (IMFs) are forces that happen between particles in different states of matter: solids, liquids, and gases. Let's break down how these forces work in each state.

1. Solids:

   • In solids, IMFs are strong. This keeps the particles tightly packed together.
   • The particles can only vibrate a little. They stay in their places.
   • For example, in ice, the particles vibrate when the temperature is around 0°C. At this temperature, they have about 3-6 kJ/mol of energy.

2. Liquids:

   • In liquids, IMFs are weaker compared to solids. This lets the particles move past each other more easily.
   • Because of this, particles can slide around, giving liquids a definite volume but no specific shape.
   • At room temperature (about 20°C), liquid water has a kinetic energy of around 5.4 kJ/mol.

3. Gases:

   • In gases, IMFs are very weak, which lets particles move quickly and freely.
   • As the temperature rises, the average kinetic energy of gas particles increases. You can think of it like this: $KE = \frac{3}{2} kT$ Here, $k$ is a constant (1.38 x 10^−23 J/K) and $T$ is the temperature in Kelvin.
   • For example, at 25°C (or 298 K), gases can have kinetic energies greater than 24 kJ/mol.

Understanding these forces helps us see how matter changes states and how energy moves around.