States of Matter: Solids, Liquids, and Gases Explained

States of Matter: Solids, Liquids, and Gases

Matter exists in three primary states: solid, liquid, and gas.

The Solid State

The solid state is characterized by fixed mass, volume, and shape because its constituent particles are strongly bonded together. These particles can vibrate slightly but cannot move freely.

• In some solids, particles are regularly arranged, forming shapes with sharp edges, vertices, and planes, which are called lattices.
• When this arrangement is visible to the naked eye, the solid is said to have formed a crystal.
• Glass and plastic possess an amorphous or glassy structure.

The Liquid State

The liquid state is characterized by fixed mass and volume, but variable shape. Liquids take the form of the container that holds them. In liquids, particles are linked, but not as strongly as in solids, allowing them to slide over each other in groups and change positions.

The Gaseous State

The gaseous state is characterized by fixed mass but variable shape and volume. The particles are widely separated from each other and move freely at high speed, thus occupying all available space.

Aggregation States of Matter

The states of matter depend on the position of the particles that constitute them, and therefore are also called aggregation states of matter.

Kinetic Theory of Particles

The kinetic theory of particles states:

1. Matter is made up of particles.
2. The particles are in constant motion.

Gas Behavior

• Expansion: Increased distance between particles, causing the gas to occupy a larger volume.
• Compression: Reduced distance between particles, causing the gas to occupy a smaller volume.

Phase Transitions

The transition from liquid to gas is called evaporation.

The temperature at which a substance boils and changes from liquid to gas (vapor) is called the boiling point, which differs for each substance. For water, the boiling point is 100 º C.

Key Transitions:

• Sublimation
• Fusion (Melting)
• Vaporization
• Condensation
• Solidification

Volume and Density Comparisons

The volume occupied by a substance in the gaseous state is greater than that held in the liquid state, which in turn is greater than that held in the solid state:

Gaseous volume > Liquid volume > Solid volume

The density of a substance in the gaseous state is lower than it is in the liquid state, which in turn is lower than it is in the solid state:

Gaseous density < Liquid density < Solid density

Water Anomaly

In the solid state (ice), water has a greater volume and a lower density than in its liquid state.

Freezing and Melting

The transition from liquid to solid is called freezing. The temperature at which a liquid solidifies is the same temperature at which the liquid melts. In the case of water, the freezing point is 0 º C.

State Change Definition

A state change is a change in the state of aggregation of matter (i.e., in the arrangement of its constituent particles), but not in its nature (the substance remains the same).