1. PHYSICAL AND CHEMICAL CHANGES
SECTION 15-4

2. A. PHYSICAL CHANGES
A change that alters the form of a substance (physical properties), but does not change it to another substance
Different states (solid, liquid, or gas),
of the same matter
CAN get it back

3. Size, Color, Shape, Density, Texture, Smell, or State
PHYSICAL CHANGES CAUSE A CHANGE IN PHYSICAL PROPERTIES SUCH AS:
Size, Color, Shape, Density, Texture, Smell, or State

4. B. CHEMICAL CHANGES
Changed into a new substance with new properties. A new kind of matter!
Bonds between atoms break, and the atoms rearrange to form new and different substances
Also called a chemical reaction
CANNOT get it back

5. TEMPERATURE, LIGHT, SOUND, ODOR, FIZZING,COLOR CHANGE
CLUES THAT A CHEMICAL CHANGE OR REACTION HAS OCCURED:
TEMPERATURE, LIGHT, SOUND, ODOR, FIZZING,COLOR CHANGE
absorbs energy releases energy absorbs energy

6. Matter changes whenever energy is added or taken away
C. ENERGY
Matter changes whenever energy is added or taken away
Thermal Energy – movement of particles
heat particles – gain thermal energy
cool particles – lose thermal energy
Chemical Energy – energy in chemical bonds
Break bonds – release energy
Form bonds – absorb energy

7. (applies to both chemical & physical changes)
LAW OF CONSERVATION OF ENERGY
(applies to both chemical & physical changes)
Total amount of energy
stays the same
Energy can change from one form to another, but energy is never lost or created

8. CONTROL THE RATE OF A CHEMICAL REACTION BY ADDING ENERGY OR TAKING ENERGY AWAY
Why is meat stored in the freezer?
What happens to milk left on the counter?
Why do we place cake batter in an oven?

9. D. CHANGES IN STATES of MATTER
GAS
VAPORIZATION
(evaporization & boiling)
CONDENSATION
Sublimation
LIQUID
FREEZING
MELTING
SOLID

10. Changing between Liquids & Solids
MELTING
Change from a solid state to a liquid state
Melting Point - Temperature at which a solid changes into a liquid
Matter absorbs thermal energy and the temperature rises
FREEZING
Change from a liquid state to a solid state
Freezing Point - Temperature at which a liquid changes into a solid
Matter releases thermal energy and temperature drops
Melting point and freezing point are the same for a given type of matter

11. Changing between Liquids & Gasses
VAPORIZATION
Change from a liquid state to a gas state
EVAPORIZATION – vaporization that takes place at the surface of a liquid
Example - Puddle drying up after a rain shower
BOILING – vaporization that takes place throughout the liquid (BOILING POINT)
CONDENSATION
Change from a gas state to a liquid state
Gas particles cool, slow down enough to be attracted to each other, and droplets form
Matter releases thermal energy

12. State Change Pyramid Gas Liquid Solid Condensation Sublimation
Absorbing
thermal energy
Releasing
thermal energy
Gas
Condensation
Sublimation
Vaporization
Melting
Freezing
Liquid
Solid

13. Why does sweating cool the human body?
(hint: liquid changes state and uses thermal energy)
Why do liquids boil at a lower temperature in the mountains?
(hint: boiling also depends on air pressure)

14. What state of matter are clouds, fog, & steam?
(hint: water vapor is invisible)
Why do orange farmers in Florida spray their crops with water to save the oranges when a night freeze is predicted?
(hint: liquid to solid, releases energy)

15. Directly from a Solid to a Gas
SUBLIMATION
Change from a solid state to a gas state, without ever becoming a liquid
Particles on the surface of a solid gain enough energy to become a gas
Examples: dry ice (solid CO2) creates fog, snow seems to disappear

16. Graphing Changes of State
THERMAL energy- temperature change
CHEMICAL energy – no temperature change
(ALL horizontal areas are phase changes)