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# 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.

#### Name

solid

liquid

melting

liquid

solid

freezing

liquid

gas

boiling

gas

liquid

condensation

solid

gas
(skipping liquid phase)

sublimation

gas

solid
(skipping liquid phase)

deposition

## 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.

### Melting

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.

### Boiling

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.

### Cooling

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:

#### Freezing (°C) - becomes a solid

H2O (water)

100° C

0° C

Fe (iron)

2750° C

1535° C

O (oxygen)

-183° C

-218° C

Hg (mercury)

357° C

-39° C

Ethyl Alcohol

78° C

-114° C

Use the converter to change °C to °F.

#### Temperature Converter

Enter a number in one box and then click anywhere outside the box.
Use the reset button to clear the numbers.

 °F: °C:

## Summary

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

### Websites

State of Matter - Wikipedia

Phase transition - Wikipedia

Resources on Matter

Matter Resources

Physics Resources

### Books

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.

## Students and researchers

www.school-for-champions.com/science/
matter_states_changing.htm

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