States of Matter - The Liquid State

A liquid is a type of fluid that cannot be easily compressed. It adjusts to the shape of its container but keeps a nearly constant volume, even with pressure changes, as long as the temperature and pressure remain constant. When a solid is heated past its melting point and is under sufficient pressure, it transforms into a liquid state. Liquids act as a transition phase between solids and gases, with water being a well-known example that can exist in all three states: ice (solid), liquid water, and water vapour (gas).

• Constituent particles are less closely packed.
• The force of attraction between particles is less strong.
• Kinetic energy between particles is more than that in solids.
• Do not have a definite shape but have a definite volume.
• Density is lower than solids and can diffuse.
• Almost incompressible.

Under normal conditions of temperature, pressure, and volume, liquids generally show the above-mentioned features. When the physical conditions change, the basic characters of liquids also undergo a drastic change. Apart from the above characteristics, liquids also show the following properties:

When a liquid is filled in a container, its walls are occupied by the vapours from that liquid. Liquids show the unique property of turning into vapours as soon as the temperature rises! Generally, vapours from the aqueous substance occupy the walls of the unfilled part of the container and exert a pressure on the walls of that container; this pressure is called the vapour pressure.

• Initially, the vapour pressure increases, but after some time it becomes constant. Gradually, an equilibrium between the liquid phase and the vapour phase is established.
• The vapour pressure at the point of equilibrium is known as the equilibrium vapour pressure or saturated vapour pressure.
• The whole phenomenon of vapour formation solely depends on the temperature and hence tends to increase with the increasing temperature.

1. Almost Incompressible: Liquids are difficult to compress because their molecules are closely packed.
2. Constant Volume, No Fixed Shape: Liquids maintain a steady volume but take the shape of their container.
3. Fluidity: Liquids can flow and move from one place to another, unlike solids.
4. Boiling Points: Under normal conditions, liquids have boiling points higher than room temperature, meaning they need to be heated to a certain point to turn into gas.
5. Intermolecular Forces: While these forces are present, they are weaker than in solids, allowing liquid molecules to move more freely and giving liquids a flexible structure.