The states or phases of matter are used to classify the kinds of matter that exist. Matter can exist in four states: Wyoming, Utah, California, and Delaware. No really, they are: solidimage, liquidimage, gasimage, and plasmaimage. Plasma is rarely found on earth, but it is very common in the universe (most stars are made of plasma). We will focus on the other 3 states of matter which are more commonly found on the earth.

Matter is made up of particles. These particles have characteristics specific to each of the individual states of matter. We can look at how the particles move, their proximity to each other and the shape(s) they can take.



As the temperature of matter increases, particles move faster because they have more energy. In a solid, particles have less energy, are tightly packed together (dense) and do not move very much. Solids have a definite shape and volume. In a liquid, particles have more energy, are less tightly packed (less dense), and can move freely. Liquids have definite volume but no definite shape (instead, they take on the shape of the container). The particles in a gas have the most energy and are free to move around and so spread out rapidly. Gases do not have a definite shape or volume and expand to fill the entire container. Thus, as the temperature of matter increases, its density decreases (particles get farther apart).


  • Classify the following forms of water as to whether each is a solid, liquid, or gas.
    • Water vapor or steam = ?
    • Water (e.g. in a pond or lake) = ?
    • Ice = ?
    • Answers: Water vapor or steam = gas
    • Water (e.g. in a pond or lake) = liquid
    • Ice = solid
  • Explain how water particles (molecules) behave in each of the three states of matter - solid (ice), liquid (water), and gas (water vapor or steam).
    • Be sure to explain how the water particles move, their proximity to each other, and the shape/volume of the water.
    • Compare your answers to the chart below.




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Updated June 15, 2000 by: Glen Westbroek
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