A cooling curve is a line

graph Graph may refer to: Mathematics *Graph (discrete mathematics), a structure made of vertices and edges **Graph theory, the study of such graphs and their properties *Graph (topology), a topological space resembling a graph in the sense of discre ...

that represents the change of phase of

matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic part ...

, typically from a gas to a solid or a liquid to a solid. The

independent variable Dependent and independent variables are variables in mathematical modeling, statistical modeling and experimental sciences. Dependent variables receive this name because, in an experiment, their values are studied under the supposition or dema ...

(X-axis) is time and the

dependent variable Dependent and independent variables are variables in mathematical modeling, statistical modeling and experimental sciences. Dependent variables receive this name because, in an experiment, their values are studied under the supposition or dema ...

(Y-axis) is temperature.Garland, Nibler, and Shoemaker. Experiments in Physical Chemistry (7th ed.) Below is an example of a cooling curve used in

casting Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a ''casting'', which is ejecte ...

The initial point of the graph is the starting temperature of the matter, here noted as the "pouring temperature". When the phase change occurs, there is a "thermal arrest"; that is, the temperature stays constant. This is because the matter has more

internal energy The internal energy of a thermodynamic system is the total energy contained within it. It is the energy necessary to create or prepare the system in its given internal state, and includes the contributions of potential energy and internal kinet ...

as a liquid or gas than in the state that it is cooling to. The amount of energy required for a phase change is known as

latent heat Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition. Latent heat can be underst ...

. The "cooling rate" is the slope of the cooling curve at any point.

References

Phase transitions Thermodynamics {{statisticalmechanics-stub