Post on 17-Jan-2016
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?