Physical & Chemical Changes

1. Physical & Chemical Changes

2. Physical Changes Physical changes are changes that alter the size, shape, location or physical state of a substance but not its chemical state.

3. Don’t Use Dem Big Words • Physical State- • Solid • Liquid • Gas • Plasma • Substance- • Stuff… something… the item you are working with

4. Physical Change A change that affects one or more physical properties. The substance is still the same substance Example: Breaking a pencil or a piece of chalk.

5. Physical Change Examples Freezing water Dissolving sugar Bending metal Mixing oil & vinegar Melting butter Most of these changes be undone?

6. So What Does That All Mean? • Ok… here’s the deal… • If the thing is still the same thing after it has been changed… • It’s a Physical Change. • Example… Boiling water Boiling Water becomes Water vapor Water = water

7. Here’s An Example… • A physical change in a substance doesn't change what the substance is. • cutting paper – • physical change in the shape and size of the paper. • It is still paper!!!!!!

8. What Other Changes are Physical? • Cutting • Tearing • Shredding • Grinding • Shrinking • Enlarging • Change in Phase • Relocating • Dissolving • Rotating • Molding (shaping)

9. Chemical Changes Chemical changes are changes that alter the chemical make up of the substance being changed.

10. Chemical Change A change that occurs when one or more substances are changed into entirely new substances with different properties. Example: Baking a cake

11. Basically What You’re Telling Me Is… If you end up with a chemical or chemicals that you did not start with, It is a chemical change!!!!!!!

12. Here’s An Example… • Burning anything… • Once something burns, it can not burn again… • Burn a piece of wood and what do you have? • Ash… not wood. Ash cannot be burned again. It is a new substance!!!

13. Another Example Is… • Eating… • Now eating can change food both physically and chemically. • Chewing is Physical but… • Once your spit touches the food chemicals in the saliva begin to change the food chemically.

14. Signs That A Chemical Change Has Occurred • Creation of a gas (bubbles) • Temperature Change • Formation of a Precipitate • Color Change • Change in Odor

15. Chemical Change Examples Soured milk Effervescent tablets Burning gases Rusting metal Can most of these changes be undone?

16. Review • Classify each of the following properties as either physical or chemical properties: • reacts with water • Boils at 100 degrees celcius • is blue • fizzes when combined with vinegar. • What are three clues that indicate a chemical change might be taking place?

17. Physical and Chemical Changes Quiz …True or False? • With a physical change, no new substance is formed.   • With a chemical change, a chemical reaction occurs. • With a physical change, energy is either given off or absorbed. • A chemical change can be easily reversed. • Eating food can be considered both physical and chemical changes.

18. Physical and Chemical Changes Quiz…Answers! TRUE • With a physical change, no new substance is formed.   • With a chemical change, a chemical reaction occurs. • A chemical change can be easily reversed. • Eating food can be considered both physical and chemical changes. TRUE FALSE TRUE