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The information below is intended to provide introductory material for elementary students and further material for high school students.

Please keep in mind that not all demonstrations are presented at each show, and each topic may not be covered.


MATERIAL SCIENCE

Introduction

Note that the properties discussed below are true in general. For a variety of reasons, some materials do not behave according to the properties discussed below. These exceptions are very important, but are too complicated to be discussed here.

  • The temperature of an object is the measure of the speed of the object's particles.

    All objects consist of many, many particles which are in constant motion. The measure of the average speed of these particles is called the temperature of the object. A very high temperature, for example, simply means that the average speed of the object's particles is very high.


  • There are three states of matter. The state an object is in depends solely on the temperature of the object. The three states, in order of descending temperature, are: gas, liquid, and solid.

    When a material is in its gaseous state, it has a relatively high temperature. Particles of a gas are moving so fast that the chemical bonds between the particles of the material are all broken. Each particle collides with its neighboring particle with great force, trying to press outwards. Due to the lack of chemical bonds, a gas will expand until it has reached the boundaries of its container.

    When a material is in its liquid state, it has a relatively moderate temperature. Particles of a liquid are moving fast enough so that they are not rigidly bound by the chemical bonds of their neighboring particles. They are, however, bound just enough so that none of the particles are able to escape from the others. Due to this, the shape of a liquid is determined by the shape of its container.

    When a material is in its solid state, it has a relatively low temperature. Particles of a solid are moving so slowly that they can not overcome the chemical bonds from their neighboring particles. The particles are bound together in a rigid pattern. Due to this, the shape of a solid is not affected by the shape of its container, nor does it exert any pressure on the boundaries of its container.


  • Warming or cooling an object in a certain material state will generally raise or lower the temperature of the object. When an object is warmed or cooled enough, however, the material state of the object may change. The temperatures at which an object will change material states are known as the melting point (or freezing point) and the boiling point (or condensation point). These temperatures are specific to each material. See below for a chart of some materials.


  • Warming or cooling an object raises or lowers the object's temperature. If the temperature of the object does not reach one of its critical temperatures, then the object will not change material states. If the temperature of the object does reach one of its critical temperatures, however, then the object will change material states. The different state changes along with the associated vocabulary is summarized in the list below.

    • Cooling a solid only lowers the temperature of the solid, the solid will not change states. The solid will, however, become more rigid.

    • Cooling a liquid to its freezing point changes the material to a solid state. This process is known as freezing.

    • Cooling a gas to its condensation point changes the material to a liquid state. This process is known as condensation.

    • Heating a solid to its melting point changes the material to a liquid state. This process is known as melting.

    • Heating a liquid to its boiling point changes the material to a gas state. This process is known as boiling.

    • Heating a gas only raises the temperature of the gas, the gas will not change states.


    More Specifically

    Substance Melting Point (oF) Boiling Point (oF)
    Alcohol, ethyl -173 172
    Copper 1981 4650
    Gold 1945 5086
    Nitrogen -346 -320
    Oxygen -362 -297
    Water 32 212
    Values taken from Tipler, Paul A. Physics, Third Edition. 1991.

    Related Demos

    The following demonstrations illustrate this physics topic:

    Sponsored by the Physics Department and the Center for Science, Mathematics, and Engineering Education -- University of Virginia