Dissolved substances are materials that have mixed evenly with a liquid, usually water, to form a solution. When a solid, like salt, is added to water, it breaks down into tiny particles that spread throughout the liquid, making it salty. This process is called dissolution, and it is essential in many natural and industrial processes. In nature, dissolved substances play a crucial role in ecosystems. For example, nutrients like nitrates and phosphates dissolve in water, providing essential elements for plant growth. Additionally, many aquatic organisms rely on dissolved oxygen to survive, highlighting the importance of these substances in maintaining healthy environments.