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Phases of Matter

According to the kinetic theory of matter, all matter is made of molecules which continuously and randomly move.
However, the amount of motion is dependent upon the state or phase of the matter.

Solid an object of fixed shape with particles that are packed tightly together; the particles vibrate or move only a little and so have the least amount of energy


a substance exhibiting readiness to flow, little or no tendency to disperse, and relatively high incompressibility; liquids possess enough energy to push other particles out of the way


a substance whose particles are spread very far apart so that they are distributed uniformly throughout any container; the particles can move freely and rapidly; gases possess a large amount of energy

Plasma -

a substance which contains ions and free electrons rather than neutral atoms; the ions and electrons are spread very far apart and are thus able to move independently of one another; plasmas possess the greatest amount of energy

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Physical & Chemical Changes

Physical changes occur when a substance changes its appearance but not its identity.

For example, when water is heated it becomes steam. This is a physical change because the chemical identity of the substance has not changed. The appearance is different, but the substance is still water.

When water changes to steam, such as at the Old Faithful geyser in Yellowstone National Park, it is a physical change.

When paper is shredded, it is a physical change because the substance is still paper.

Shredding paper is a physical change.

Altering the shape, form, volume or density of a substance are all examples of physical changes.

Chemical changes occur when a substance’s identity is changed.

If paper is burned, it is a chemical change because the substance is no longer paper. If water is reacted with a metal, it is no longer water because it reacts to form a metal oxide and hydrogen gas.

One way to tell if there has been a chemical change is to notice any color change. For example, when metal such as copper oxidizes, it turns from a copper-red color to green. The Statue of Liberty is one example of copper oxidizing. It now looks green, but when it was first made, it was bright copper-colored!

Lady Liberty is made of copper, but she now looks green because the chemical change of oxidation has changed her color.

Another way to tell if there has been a chemical change is if there is a temperature change of the substances involved. For example, when combining baking soda and vinegar, the temperature of the combination goes up. That is, heat is produced.

When baking soda and vinegar are combined, another thing happens that is evidence of a chemical change: a gas is produced. Other chemical changes where a gas is produced include burning wood, baking a cake, and putting effervescent tablets in water.

Formation of a solid is another evidence of a chemical change. Rust is a solid that forms when metal, such as a nail or a screw, reacts with water.

A rusted screw shows evidence of a chemical change.

When chemical changes occur, new substances with different characteristics from the original substances are produced.
Roy Manning,
Mar 20, 2011, 1:45 PM