Beacon Lesson Plan Library

State of Matter

Carol Houck


Students examine how atoms change from solid to liquid to gas.


The student knows that atoms in solids are close together and do not move around easily; in liquids, atoms tend to move farther apart; in gas, atoms are quite far apart and move around freely.


Each group will need:
- a flask
- source of heat
- ice
- a balloon


1. Materials should be placed in a central location for easy distribution.
2. Ice should be made in advance.


Knowledge and Skills:
- Students will be able to compare and contrast the three states of matter.
- Students will understand the concept of density, and relate it to the physical nature of matter.
- Students will relate the transfer of energy to molecular motion and molecular packing.
- Students will relate the states of matter to the transfer of energy.

1. Students will work in groups of two or three.
2. Have students place a flask, half-filled with broken ice cubes, on a hot plate. Instruct them to cover the opening of the flask with the end of a balloon. Have students record initial observations.
3. Have the students heat the ice until it turns slowly to water and then to steam. Instruct students to record observations every minute until the water begins to boil. Observations should include the condition of the ice, the volume in the flask and the condition of the balloon.
4. Have students carefully remove the flask of boiling liquid, and place it on an insulated pad or in an ice bath. Have students continue to record their observations each minute until the flask is cool.
5. Debrief by discussing findings with the class. Discussion should center around the objectives of the lesson. (See Knowledge and Skills.)


Assessment questions may include:

1. Which statement best explains why solids are more dense than liquids?
a. Solids have large spaces between molecules which allow them to take shape.
b. Liquids have large spaces between molecules which allow them to flow.
c. The molecules of solids are moving much faster than the molecules of liquids.
d. The molecules of liquids are moving much slower than the molecules of solids.

(answer b. Liquids are less tightly packed.)

2. Which of the following may cause a liquid to become a gas?
a. Energy is transferred into the liquid.
b. Energy is lost from the liquid.
c. The molecules of the liquid are slowed.
d. Energy is lost from the gas.

(answer a. Energy is transferred into the liquid, thereby increasing molecular motion and spacing.)

3. Based on our class observations, which would be a correct statement?
a. The balloon's volume should increase as molecules move closer together.
b. The balloon's volume should decreases as the flask is heated.
c. The balloon's volume should increase as the flask is cooled.
d. The balloon's volume should decrease as molecules move closer together.

(answer d. Molecules move closer together as the flask cools; the balloon's volume will decrease.)

4. Which of the following is a correct order for the kinetic energy associated with the states of matter?
a. solid>liquid>gas
b. liquid>gas>solid
c. gas>liquid>solid
d. solid>gas>liquid

(answer c. The kinetic energy, molecular motion of a gas, is greater than a liquid, which is greater than the corresponding solid.)

Assessment solution:
The molecules of a solid are tightly packed, those of a liquid are less tightly packed and those of a gas are the least tightly packed of the three. Adding energy to a solid increases the motion of its molecules which increases the distance between the molecules which causes a change of phase. The distance between molecules may be defined as density, the mass, or number of molecules in a given volume.


-Studies indicate that deep ocean currents are caused by the different densities of hot and cold water. Satellites track ocean temperature differences near and at the surface. Create a report answering these questions: Does the temperature drop at a steady rate as depth increases? What is upwelling? Where are the coldest currents? Where are the -hot spots- on the ocean floor? How does temperature affect deep currents?
-Weather is dependent on differences in the density of air due to temperature differences. Do some research to answer these questions: What factors cause a front? What is air pressure? How can you use an air pressure reading to show a hurricane is on its way or has passed?
-Make some ice cream. Why is it harder to push a spoon through the frozen ice cream than through the liquid with which you started? What is the relationship between heat and state of matter?
-Construct a replica of an ice crystal. Almost every kind of matter becomes more dense as its temperature drops. Why does ice float? Is the solid less dense than the liquid? Why would this be?
-Do all things -melt- when they reach a certain temperature? Does iron -melt-? Does wood -melt- or does something else happen? Do a presentation to the class explaining -melting points- and combustion.
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