1. Chemical and Physical Changes

2. DEMOS
Write down your observations during the DEMOS your teacher does on your Lab Sheet under EVIDENCE of a change.
Determine if you believe the DEMO shows a CHEMICAL or PHYSICAL change or BOTH.

3. DEMO
What happens when you mix sulfuric acid and table sugar?

4. The Difference
Physical Change – matter changes form but is still made of the same molecules, typically reversible
Chemical Change – a change in the molecules occurs, cannot be reversed

5. How can you tell which change it is?
Chemical Change - Substance changes into something new. You can tell because of color change, heat or light given off or taken in, precipitate, gas bubbles; new substances form.
Physical Change - Substance doesn’t change to something new, it may change form, shape, size or phase but it is still the same stuff. It is reversible and sometimes requires heat from the outside to make it happen but does not release heat by itself.

6. Physical Changes
Physical Change – matter changes form but is still made of the same molecules, typically reversible
Example:
An ice cube melting
Solid H2O  Liquid H2O
Both the beginning and ending products are made of H2O, the molecules stayed the same

7. Physical Changes
Physical Change – matter changes form but is still made of the same molecules, typically reversible
Example:
A bag of potatoes is
squished up to make
mashed potatoes

8. Physical Changes EXAMPLE:
The digestive system is very muscular and causes physical changes starting with chewing and continuing with churning in the stomach

9. Chemical Changes
EXAMPLE: The digestive system also causes chemical changes by using enzymes and chemicals to break the food down into its components

10. Evidence of a Physical Change
There are three signs that a physical change has occurred (remember, this means that your starting and ending molecules are the same)
Change in Size
Change in Shape
Change in Phase of Matter

11. Evidence of a Chemical Change
There are five signs that a chemical change has occurred (remember, this means that your starting and ending molecules are different)
Change in Temperature
Change in Color
Change or Creation of Odor
Formation of a Precipitate (a solid material)
Formation of a Gas

12. Chemical or Physical Change?

13. Chemical or Physical Change?

14. Chemical or Physical Change?

15. Chemical or Physical Change?

16. Chemical or Physical Change?

17. Chemical or Physical Change?

18. Chemical or Physical Change?