In a liquid, atoms or molecules are held close together with little space between them. As a result, liquids, unlike gases, have definite volumes and cannot easily be expanded or compressed. However, the molecules can still move around and are in a state of relative disorder. Consequently, a liquid can change shape to fit its container, and its molecules are able to diffuse and evaporate.
One of the most important properties of liquids is their ability to mix, both with each other and with other phases, to form solutions. The degree to which two liquids can mix is called their miscibility. Oil and water are almost completely immiscible because of their polarity difference. Oil and water normally form separate layers when mixed, with oil on top because it is less dense. Under extreme conditions, such as violent shaking, two immiscible liquids can form a fairly homogeneous mixture called an emulsion. Although they look like solutions, emulsions are actually mixtures of discrete particles too small to be seen distinctly.