1. Created and adapted by: Mrs. Dube
Chemical & Physical Changes
Created and adapted by:
Mrs. Dube
Edited By: Nick Dassaro

2. Physical Changes
After a physical change, the substance is still the same substance
Changes in state are physical changes
The substance may have some different properties after a physical change

3. Physical Changes

4. Chemical Changes Chemical changes are also known as chemical reactions
A change that produces one or more new substances is a chemical change or a chemical reaction

5. Chemical Changes
Electrolysis of water is an example of a chemical change that water undergoes
Water is broken down into hydrogen and oxygen using an electric current to break the bonds

6. Comparing Chemical and Physical Changes
Physical changes – no new substances are formed; the water changed state and became ice; the water froze!
Chemical changes – a new substance is formed; water chemically changed by breaking and rearranging bonds into hydrogen peroxide

7. Quick Check for Understanding
Compare and contrast chemical and physical changes. Give an example of a chemical and physical change from your daily life.

8. Chemical Reactions
A chemical reaction produces new substances by changing the way in which the atoms are arranged
New arrangements of atoms form different substances

9. Chemical Reactions

10. Reactants And Products
Reactants are the substances present at the beginning of a chemical reaction
Products are the substances formed by a chemical reaction present at the end of a chemical reaction

11. Evidence Of Chemical Reactions
Color change
Formation of a precipitate (a solid product)
Formation of a gas (sometimes seen as bubbles)
Temperature change
Production of odor

12. Quick Check for Understanding
How do reactants differ from products?
How can you tell that a chemical reaction has occurred?

13. Chemical Reaction Rates
Rates of chemical reactions can vary
Many factors affect reaction rates such as: concentration, surface area, temperature, and the presence of a catalyst

14. Concentration
Concentration measures the number of particles present in a certain volume
A high concentration of reactants means that there is a large number of particles that collide and react during a chemical reaction

15. Surface Area Surface area affects the rate of chemical reactions
Breaking a large piece of material into smaller parts increases the surface area of the material which increases the reaction rate

16. Temperature
Reaction rate can be increased by making the particles move faster
Faster moving particles have more collisions with greater force
Adding energy to the reactants raises the temperature and causes reaction rate to increase

17. Catalysts
A catalyst is a substance that increases the rate of the chemical reaction but is not consumed in the chemical reaction

18. Quick Check for Understanding
What factors impact reaction rate?
How does surface area affect the rate of a reaction?
What is a catalyst?