1. Chemical and Physical Changes

2. Chemical vs. Physical Changes
Physical Change – involves a change in appearance but does not involve creation of new materials.
Chemical Change – involves the formation of new materials.

3. Examples of Physical Changes
Changes in state – i.e., a solid melting into a liquid and then evaporating into a gas
Melting and solidifying of wax
Sharpening a pencil
Tearing up paper
Rock breaking into several pieces

4. Examples of Chemical Changes
Rusting
Digesting food
Burning materials
Fruit ripening
Mineral formation in igneous rock

5. Chemical Changes
The process that brings about a chemical change is called a chemical reaction
The new materials that get created are called products and the starting materials are called reactants
Chemical changes are usually not easy to reverse

6. Chemical Changes
Chemical reactions are characterized by a number of changes including:
Color changes
Formation of a precipitate (cloudy solution)
Formation of gas (bubbles)
Release of light
Release of heat

7. Chemical Changes
There are many words associated with chemical changes. Some examples include:
Burned, burning, burns
Changed, changing, changes
Combined, combining, combines
Formed, forming, forms, formation

8. Chemical Changes
For each of the following sentences, find the word that indicates a chemical change occurred.

9. Sentence #1 Gasoline in cars is burned, releasing gases into our atmosphere

10. Sentence #2
Rust forms on an iron pipe after being exposed to moist air for many years.

11. Sentence #3 Nitrogen oxide emissions combine with water vapor, producing nitric acid

12. Reflect and Review
What is the difference between chemical and physical changes?
Name two examples of chemical changes.
Name two examples of physical changes.
What are 5 characteristics of a chemical change?
List three words that are commonly associated with chemical changes.