1. Physical Changes & Chemical Changes
Today, we are going to study chemical changes and how they differ from physical changes. Unlike a physical change, when a chemical change occurs, the new substance may have properties that differ from the original materials.

2. Physical Change
A physical change takes place when a substance changes in size, shape or form. The particles of matter do not change.
Cutting Paper
A physical change takes place when a substance changes in size, shape, or form. However, the particles do not change. Examples of physical changes are chopping vegetables, drying clothes, or cutting paper. In each of these cases, the original substance is just altered, not changed completely.
Chopping Vegetables
Drying Clothes

3. Key Words Associated with Physical Changes
Cutting
Boiling
Freezing
Ripping
Tearing
Crumbling
There are several key words that are associated with physical changes: cutting, boiling, freezing, tearing, ripping, and crumbling. None of these things changes the matter of the original substance.

4. Chemical Change
A chemical change takes place when a substance is completely altered. The particles of matter do change.
Rotting Food
A chemical change, on the other hand, takes place when a substance is completely altered. In a chemical change, the particles of matter do change. Some examples of a chemical change are a rusting car, burning wood, and rotting food. These changes are not reversible.
Car with Rust
Wood Burning

5. Key Words Associated with Chemical Changes
Burning
Rusting
Chemicals
There are a few terms that are associated with chemical changes: burning, rusting, and chemicals.

6. Physical and Chemical Changes
Physical Change Chemical Change
Is there a change in
color?
Yes No
Do the molecules
change? No
Yes
Is a new substance created? No
Yes
Let’s go through this chart together. (Go through each question of the chart with students.)
Is it easily reversible?
Yes No
Are there phase changes?
(freezes, boils, evaporates, condensates)
Yes No

7. Physical and Chemical Changes
Identify whether it is a physical or chemical change.
A change that takes place when a substance changes in size, shape or form. The particles of matter do not change.
Physical Change Chemical Change
A change that takes place when a substance changes in size, shape or form. The particles of matter do not change.
A change that takes place when a substance is completely altered. The particles of matter do change.
Sawing Wood
Sun burned skin
Burning Wood
Adding salt to water
Let’s complete one last activity. I’m going to show you a picture and you have to raise your hand to tell me whether it is a physical change or a chemical change. (Go through each picture and wait for student responses.) Good job. Remember, a substance that goes through a physical change will change only in size, shape, or form; but, a substance that goes through a chemical change, will be altered completely.
Adding dirt to a puddle
Car Burning Gas
Baking a pie