# States Of Matter

Last Updated on February 14, 2024.

There are three main states of matter: liquid, solid, and gas.

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Changes in pressure, composition, or temperature may result in a change of state.

1. What are the possible states of matter?
A.
B.
C.
D.

Question 1 of 2

2. Which states of matter have no fixed shape and no fixed volume?
A.
B.
C.
D.

Question 2 of 2

This lesson is provided by Onsego GED Prep.

Next lesson: Work, Heat and Energy
This lesson is a part of our GED Science Study Guide

### Video Transcription

The Macroscopic Definitions are:

Gas
Gas doesn’t have a definite volume or shape and is easily compressible.

Liquid
Liquids have a constant volume, not a definite shape, and are slightly compressible.

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Solid
Solids have definite volumes and shapes and are rigid and very difficult to compress.

The Microscopic Definitions are:

Gas – In gas, the molecules are far apart, and they move rapidly and frequently while colliding with the other molecules.

Liquid – In liquids, the molecules are close together (even touching one another), but they’re still moving. The arrangement of the neighboring molecules is changing rapidly.

Solid – In solids, all molecules are held in place rigidly, and the neighboring molecules may change just very slowly or often, they’re not changing at all.

Classification of Matter

All of our Earth’s matter is classified as either a pure substance or a mixture, and a mixture can be heterogeneous or homogeneous. Pure substances may either be compounds or elements.

We cannot separate Pure Substances into component parts through physical methods. So we follow the constant composition law.

The basic reason behind this sort of property lies in the fact that pure substances are containing just one single molecule type.

We can divide Pure Substances into two main categories:
Elements – Elements are containing just one atom type.
Compounds – Compounds are containing more than just one atom type.

But there are exceptions. These include:
Elements – Gold (Au), Oxygen (O2), Diamond (C), Silicon (Si)
Compounds – Ethanol (C2H6O), Water (H2O), Quartz (SiO2)

Mixtures are having variable compositions and may be separated by physical methods into component parts. Mixtures are containing more than just one molecule type.

Mixtures may as well be divided into two main categories:

Homogeneous – the properties and composition of these mixtures are uniforms
Heterogeneous – These mixtures have non-uniform properties and composition

We call homogeneous solutions also solutions. Most people, when hearing the word solution, are thinking of liquids. In fact, though, solutions may occur in all states of matter, solid, liquid, and gas.

Examples are including:

Air – the principal components of air include N2, O2 & CO2
Vodka – The principal components of Vodka are water and ethanol
Brass – Brass is a solid solution of Zn and Cu
Ruby – Ruby is a solid solution of Cr2O3 and Al2O3.

To get an idea of the “variable composition” principle, just think of one of the differences between Everclear (5% Water and 95% Ethanol) and Vodka (some 60% Water and 40% Ethanol).

Both these compositions are homogeneous mixtures of ethanol and water, but there’s a huge difference in the concentration of ethanol between the two compositions.

Unlike the situation in solutions, the heterogeneous mixture composition is varying from point to point.

Some examples are including:
Wood, Concrete, Chocolate chip cookies, and Rocks

Note: For passing the GED Science test, students need to know about the three main physical states of matter: solid, liquid, and gas.

There is also a fourth main state of matter, plasma, a hot, charged gas (plasma). Plasma is consisting of positively charged ions with free electrons. Today, scientists have discovered as many as eight states of matter, and the number goes up as science advances.

All Earth’s matter is either classified as a pure substance or a mixture. Mixtures can be homogeneous or heterogeneous. Pure substances may be either elements or compounds.