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liquid

By Robert Sheldon

What is a liquid?

A liquid is a type of matter with specific properties that make it less rigid than a solid but more rigid than a gas. A liquid can flow and does not have a specific shape like a solid. Instead, a liquid conforms to the shape of the container in which it is held. Although this is similar to a gas, a liquid does not expand to fill up the container like a gas. Examples of liquids at room temperature (about 20 degrees Celsius or 68 degrees Fahrenheit) include water, oil, alcohol and mercury.

The term liquid can refer to the type of substance or to its state of matter. Water, for example, is the most common liquid on Earth and, in its liquid state, covers a substantial percentage of the surface. However, it is in a liquid state only between the temperatures of 0 degrees Celsius (32 degrees Fahrenheit) and 100 degrees Celsius (212 degrees Fahrenheit). At lower temperatures, it transitions to a solid state and becomes ice (frozen water). At higher temperatures, it transitions to a gaseous state and becomes water vapor.

Whether frozen or vapor, the molecular structure of water remains the same as in its liquid state. Every form is still water, just in different states of matter. However, frozen water and water vapor are not liquids, nor are they in a liquid state.

When matter is in a solid state, the atoms or molecules are packed together more tightly than matter in the liquid state, but the difference between their densities is relatively small, just enough so the molecular entities in a liquid can move around each other. In a gas, the molecular entities are spread much further apart and move and expand more freely within their available space.

When a liquid is heated, the molecular entities gain kinetic energy. If the temperature rises enough, the liquid becomes a gas or reacts with chemicals in the environment. For example, water becomes gaseous when it is heated gradually, but alcohol can combust when combined with oxygen if heated suddenly and dramatically. When a liquid is cooled, the molecular entities lose kinetic energy. If the temperature becomes low enough, the liquid becomes a solid.

What are characteristics of a liquid?

Liquids can vary substantially from each other. For example, olive oil weighs more than vinegar and is much thicker, causing it to pour more slowly. Olive oil also starts to solidify around 12 degrees Celsius (54 degrees Fahrenheit), whereas vinegar starts to freeze at around -2.2 degrees Celsius (28 degrees Fahrenheit). Despite the differences between liquids, they can generally be characterized by a set of common physical properties:

What are mixtures?

Liquids are often combined to create mixtures. A mixture is either heterogeneous or homogeneous. A heterogeneous mixture is a combination of substances that do not react chemically with each other. The individual materials are not distributed uniformly, and they retain their individual physical properties, as in the case of oil and vinegar.

A homogeneous mixture, also referred to as a solution, is a type of mixture in which the substances are uniformly distributed and undergo a chemical change. Typically, one substance dissolves into the other to form a new substance with a uniform composition. For example, vodka is a solution made of ethanol and water.

See also: state of charge, Standard temperature and pressure, impedance, coulomb, water cooling, matter, compound, proton, neutron, dielectric material and conductor.

08 Dec 2022

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