Lesson 5:Changes in Matter

The Law of Conservation of Matter and Energy tells us that matter and energy cannot

be created or destroyed.But matter can be changed!

Changes in matter can be classified as either physical changes or chemical changes.

A physical change is a change in matter that does not affect its

chemical composition.

After a physical change, a

substance may look different,

but it is still the same substance!

You can melt ice and then refreeze the water to make ice again. The ice changes states but it is always water. You can tear

up a piece of paper and it’s still paper. You can mix sugar in water and still taste that the sugar is there. These are all physical

changes. Physical changes mean that matter has changed states but remains the

same.

Discovery Education Video:Physical Change

Discovery Education Video:Physical Changes

Examples of Physical Changes:

Crushing a Can Melting an Ice Cube

More Examples of Physical Changes:

Boiling Water Mixing Sand and Water

More Examples of Physical Changes:

Breaking a Glass Shredding Paper

More Examples of Physical Changes:

Chopping WoodMixing Red and Green Marbles

A chemical change is a process that

changes a substance into a new substance

through a chemical reaction.

Thermite Reaction

A chemical change changes the bonds of the molecules that make up a substance.

As the molecules bond together

differently, new substances will be

created

You light a fire while you camp to keep warm and to cook. You also see a chemical change. Once the

wood turns to ashes, it cannot turn back into wood. The wood has

become something different. That’s what happens in a chemical change.

Discovery Education Video:Chemical Change

Examples of Chemical Changes:

Rusting of Iron Burning of Wood

More Examples of Chemical Changes:

Baking a Cake Exploding Fireworks

More Examples of Chemical Changes:

Baking Soda and Vinegar

Rotting Bananas

Discovery Education Video:

Changes in the Properties of Matter

Changes in Matter Key Questions:

1) What is the difference between a physical and a chemical change?

2) Can all changes in matter be undone? Explain your answer.

3) What are some examples of changes in matter that you have observed. Were these physical or chemical changes? How do you know?