States of Matter
We look at five states of matter on the site. Solids, liquids, gases, plasmas, and Bose-Einstein condensates (BEC) are different states of matter that have different physical properties. Solids are often hard, liquids fill containers, and gases surround us in the air. Each of these states is also known as a phase.
How does matter change from one state to another? Elements and compounds can move from one state to another when specific physical conditions change. For example, when the temperature of a system goes up, the matter in the system becomes more excited and active. If enough energy is pushed into a system, a phase change may occur as the matter moves to a more active state.
Let’s say you have a glass of water (H2O). When the temperature of the water goes up, the molecules get more excited and bounce around a lot more. If you give a liquid water molecule enough energy, it escapes the liquid phase and becomes a gas. The extra energy allows the molecules to change states.
Have you ever noticed that you can smell a turkey dinner after it starts to heat up? As the energy of the molecules inside the turkey heat up, they escape as a gas. You are able to smell the volatile compounds that are mixed in the air around you.
It’s About the Physical"Phase" describes the physical state of matter. The key word to notice is "physical". Matter only moves from one phase to another by physical means. If energy is added (increasing the temperature) or if energy is taken away (freezing something), you can create a physical change.
Changing the pressure of a system is another way to create a physical change. If you place a glass of liquid water on a table, it will just sit there. If you place a glass of water in a vacuum chamber and lower the pressure, you can begin to watch the water boil and the water molecules move to a gas phase.
When molecules move from one phase to another they are still the same substance. There is water vapor above a pot of boiling water. That vapor (or gas) can condense and become a drop of liquid water in the cooler air. If you put that liquid drop in the freezer, it would become a solid piece of ice. No matter what physical state it was in, it was always water. Even though the physical state changed, the chemical properties were the same.
On the other hand, a chemical change would build or break the chemical bonds in the water (H2O) molecules. If you added a carbon (C) atom, you would create formaldehyde (H2CO). If you added an oxygen (O) atom, you would create hydrogen peroxide (H2O2). Neither new compound is anything like the original water molecule. Generally, changes in the physical state do not lead to any chemical change in compounds.
States of Matter Examples
A Liquid OceanThere are many liquids around you. Oceans, lakes, and rivers are good examples of liquid water (H2O). Planetary scientists are looking for other planets that have liquid water, but planets require very specific conditions to have water as we know it.
Solids in CeramicsCeramic bowls are a great example of a solid. Did you know that pieces of pottery make up many of the items found from ancient civilizations? Ceramic materials are usually made from soft clay that is heated up and then slowly cooled. The clay becomes very hard because water (H2O) is removed and the chemical bonds inside the clay change.
Plasmas on the SunPlasmas are highly energized gases that have lost their electrons. Stars, including the Sun, are covered in plasma. Hydrogen (H) and helium (He) ions float around the Sun with their electrons moving freely.
Gases in BalloonsBalloons aren’t technically gases. They are little pieces of rubber. However, the helium (He) inside the balloon is a gas. Helium is a noble gas that has a very low atomic mass. In its gaseous state, it is lighter than air. The helium atoms have a lower mass than the nitrogen (N2) and oxygen (O2) molecules that fill most of our air. The lower mass and lightness helps balloons to float.
SfC Home > Physics > Matter >
Changing States of Matter
By Ron Kurtus (revised 29 March 2012)
A material will change from one state or phase to another at specific combinations of temperature and surrounding pressure. Typically, the pressure is atmospheric pressure, so temperature is the determining factor to the change in state in those cases.
Names such as boiling and freezing are given to the various changes in states of matter. The temperature of a material will increase until it reaches the point where the change takes place. It will stay at that temperature until that change is completed.
Questions you may have include:
- What are the changes in states called?
- How does temperature change when the states change?
- What are some common temperatures to change the state?
This lesson will answer those questions. Useful tool: Units Conversion
Changes in states
The states of matter are solid, liquid, gas and plasma. Since there is some debate on whether plasma should be classified as a state of matter and since it is not commonly experienced, we will not discuss its properties here.
Order of changes
When heat is applied to a material, its change in state typically goes from solid to liquid to gas. There are some exceptions where the material will go directly from a solid to a gas.
When a material is cooled, its change in state typically goes from gas to liquid to solid. There are some exceptions where the material will go directly from a gas to a solid.
Names of changes
Each change in the state of matter has a specific name.
Change in temperature
When a material reaches the temperature at which a change in state occurs, the temperature will remain the same until all the energy is used to change the state.
When a solid is heated, its temperature rises until it reaches its melting point. Any additional heat added to the material will not raise the temperature until all of the material is melted.
Thus, if you heat some ice, its temperature will rise until it reaches 0° C (32° F). Then the ice will stay at that temperature until all the ice is melted. The heat energy is used to melt the ice and not to raise the temperature. After the ice is melted, the temperature of the water will continue to rise as more heat is applied.
When a liquid is heated, its temperature rises until it reaches its boiling point. The temperature will then remain at that point until all of the liquid is boiled away.
For example, the temperature of a pot of water will increase until it reaches 100° C (212° F). It will stay there until all the water is boiled away. The temperature of the steam can then be increased.
Likewise, when a gas is cooled, its temperature will drop until it reaches the condensation point. Any additional cooling or heat loss will not lower the temperature until all of the gas is condensed into the liquid state.
Then the temperature of the liquid will continue to drop as more cooling is applied. Once the liquid reaches the freezing point, the temperature will remain at that point until all of the liquid is solidified. Then the temperature of the solid can continue to decrease.
Boiling and freezing temperatures
The boiling and freezing temperatures of some common materials at normal atmospheric pressure are:
Use the converter to change °C to °F.
The names of the changes in state are melting, freezing, boiling, condensation, sublimation and deposition. The temperature of a material will increase until it reaches the point where the change takes place. It will stay at that temperature until that change is completed. A material will change from one state to another at specific combinations of temperature and surrounding pressure, typically at atmospheric pressure.
Sometimes change can be good
Resources and references
Ron Kurtus' Credentials
State of Matter - Wikipedia
Phase transition - Wikipedia
Resources on Matter
Top-rated books on Matter
Top-rated books on Physics
Top-rated books on States of Matter
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