State of Matter

The state of matter refers to the physical form in which a substance exists, such as solid, liquid, or gas. These states are determined by the arrangement and movement of the particles that make up the substance.

States of Matter

• Solid: In this state, particles are tightly packed together in a regular pattern, and they vibrate in place. Solids have a definite shape and volume.
• Liquid: Particles in a liquid are close together but can move past each other. Liquids take the shape of their container and have a definite volume.
• Gas: Gas particles are spread out and move freely. Gases do not have a definite shape or volume and expand to fill their container.

Changes in State

Substances can change states through the processes of melting, freezing, evaporation, condensation, and sublimation.

Melting and Freezing

When a solid is heated, it melts and becomes a liquid. When a liquid is cooled, it freezes and becomes a solid. The temperature at which a substance melts or freezes is its melting point.

Evaporation and Condensation

Liquids can change to gases through evaporation, and gases can change to liquids through condensation. Evaporation occurs at the surface of a liquid, while condensation occurs when a gas cools and forms droplets. The temperature at which a substance condenses or evaporates is its boiling point.

Sublimation

Some substances can change directly from a solid to a gas through sublimation, and vice versa. Dry ice is an example of a substance that undergoes sublimation.

Study Guide

1. Define the term "state of matter" and give examples of each state.
2. Explain the changes in state that occur during melting, freezing, evaporation, condensation, and sublimation.
3. Compare and contrast the properties of solids, liquids, and gases.
4. Discuss the importance of understanding the states of matter in everyday life and scientific research.