Evaporation and Condensation

Evaporation, Condensation, Freezing and Melting Science MatchCard

Explore the states of matter with the Evaporation and Condensation Matchcard.

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Freezing, Melting, Evaporation
and Condensation MatchCard

Objective: Explain how molecules change when a substance freezes, melts, evaporates, and condenses.

This cool science experiment will demonstrate some of the changes a substances undergoes as it changes from solid to liquid to gas.

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Freezing and Melting MatchCard

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This is MatchCard #6 of the Light and Energy Unit Study. Find more information on MatchCard Science below.

Experiment with the States of Matter

Freezing

With the first part of this experiment, the student will examine how a liquid changes as it freezes into a solid. Two re-sealable sandwich bags are used as the water changes to the other states and back again.

• Measure one cup of water into each bag.
• Remove most of the air from the bags.
• Put one bag in the freezer and leave the other at room temperature. Give several hours for the water to freeze.
• Examine the bags. Note how the ice takes up more of the bag than the water.

Explain that the molecules in the ice got closer together, until they joined in a lattice-shaped form.

Human Demonstration

Illustrate this by holding on to each other with outstretched arms and elbows locked straight out. You are far from each other.

The liquid state can be illustrated by pulling your arms in with your elbows bent. You can touch each other's arms with your elbows. You are allowed to move around, but keep touching each other's arms. You are closer together, but moving more. You are also not as tightly connected.

Melting

Melting is one of the easiest transitions of the states of matter to understand.

• Let the bag with ice sit out at room temperature.
• Let younger students predict what will happen.
• When the water has melted, notice the water level compared to the mark on the bag.
• Remeasure it to see that it is still one cup.

Use the Evaporation and Condensation MatchCard to illustrate the temperature changes that occur as substances move from the solid to liquid to gaseous state.

Evaporating

Now let's return to our sandwich bag. This can be done with a stove top or microwave. As an alterative, the bag can be placed in a full pot of boiling water.

• Be careful to avoid skin burns with this experiment.
• If using the stove top, add water to a pan, bring the water to boil, and add one bag of water to the pan.
• This can be done in the microwave as well.
• Note that as the water evaporates the bag expands from the water vapor.

Alternative Boiling Experiment

You will need a thin glass bottle with a narrow mouth and a large balloon (not the tiny water sized balloons.) You will also need a pan of water, a stove, and adult supervision.

• Place the open end of the balloon over the mouth of the bottle, sealing the bottle with the balloon.
• Turn the stove on high, and boil the water.
• Put one half to one cup of water in the bottle.
• Carefully put the bottle into the pan of boiling water.

Explain that as molecules heat up, they move faster. They get further apart and have no bond with each other.

Human Demonstration

Illustrate this with a group of blind folded people playing group tag in a room. You are not connected, you are moving quickly, you bump into each other, and you take up more space.

Condensation

Condensation occurs as a substance in the vapor state (gas) is cooled and returned to a liquid state.

• Chill a bowl in the refridgerator or freezer. Or you can put ice cubes in a bowl.
• Put the hot bag expanded with water vapor into the cold bowl.
• Watch the water drops form along the side of the bag that is being cooled.

Alternative Condensing Experiment

Put a metal spoon in the freezer to chill. Then boil water on the stove top. When you see the steam, hold the chilled spoon over the steam. The water vapor will cool and liquify on the spoon.


Point out the illustrations on the Evaporation and Condensation MatchCard to show the movement of molecules as the states of matter change.

The Hunt

• Brainstorm situations where they have seen substances freeze, melt, evaporate, and condense.
• Make a list.
• Have a six week hunt. See who can point out situations when a substance is moving from one state to another.
• Condensation is the hardest to recognize. Here are a few situations you may wish to point out if the students don't find them:
  • condensation on the outside of an ice cold glass on a hot day
  • condensation on the inside of a windshield on a cold day
  • fog on your glasses when you go into hot air or open the stove
  • fog
  • dew on the grass

Additional idea: Illustrate or photograph some of these scenarios.