physical & chemical changes. what is a physical change? in physical changes, matter may look,...

Physical & Chemical Changes

What is a physical change?

•In physical changes, matter may look, act, or feel different. But it is still the SAME thing.

•The molecules have NOT changed.

Types of Physical Changes

• Breaking• Crushing• Cutting• Bending• Melting• Freezing• Boiling

Examples of Physical Changes

• If you tear, fold, or crumple a piece of paper, it looks different. But it is still a piece of paper.

• If you break, sharpen, or chew on a pencil, it looks different. But it is still a pencil.

Ice can change to water. Water can change to ice. It’s still H2O either way.

Liquid water can change to water vapor when it is heated.

Water vapor can change to liquid water when it is cooled.

It’s still H2O either way.

What is a chemical change?

•In chemical changes, matter becomes something completely different.

•The molecules have changed.

Examples of Chemical Changes

• Think about baking a cake. The batter is a liquid mixture of flour, sugar, water, and other ingredients. When you heat it in the oven, the batter turns into a yummy solid. You can’t ever change it back into flour, sugar, water, and other ingredients. The batter has become something new.

•If you leave iron out for a long time, it will rust.

•When fireworks change colors, a chemical change is happening.

•If you light a match, it can never be the same again.

Examples of Chemical Changes

Show Me!

•Draw an example of a physical change.

•Draw an example of a chemical change.

You Decide!frying an

egg

This is a chemical change. The egg can never go back to the way it was before.

boiling water

This is a physical change. The

water vapor that is produced will condense into

liquid water when it cools.

burning gasoline

This is a chemical change. Once your

car has used the gasoline, it can never

be used again.

breaking glass

This is a physical change. It looks

different, but it’s still glass.

compressing (squeezing)

a spring

This is a physical change. It looks

different, but it’s still a spring.

souring milk

This is a chemical change. Rotten foods

and drinks can never go back to the way they

were before. One big clue is the smell. Strong odors can be a sign of a

chemical change.