1. Physical & Chemical Changes
Chapter 3
Physical & Chemical Changes

2. Properties of Matter
Physical Properties are characteristics of a substance that can be observed without changing the identity of the substance.
Ex. Wood is wood whether it is in a house, a toothpick or a baseball bat.
Physical Properties that you already learned about:
Mass
Volume
Density
Weight
Also, color, texture, hardness, shape, etc.

3. Section 1 - Another Important Physical Property of Matter that we need to study is the…
Phases of Matter
There are 4 phases of matter:
Solid
Liquid
Gas
Plasma

4. Section 1 - Solids Have a definite shape and a definite volume
Particles (molecules) are packed very close together so no movement can occur except vibrations.
2 types
Crystalline solids have particles arranged in regular repeating patterns, ex table salt, quartz
Amorphous solids have particles that aren’t arranged in a rigid way, so they can flow slowly, ex – candle wax, silicone rubber.

5. Section 1 - Liquids
Do not have definite shape, but do have a definite volume
Particles are close together, but not as close together as a solid.
The particles can move past one another, thus allowing it to flow.
They take the shape of the container they are in.
One important Property of liquids is viscosity
Viscosity – the resistance of a liquid to flow; ex honey has a higher viscosity than water.

6. Do not have definite shapes or volumes.
Section 1 - Gases
Do not have definite shapes or volumes.
Particles are very far apart and move very freely.

7. NOTE: Plasma TV’s ARE NOT made of Plasma!!!!
Section 1 - Plasma
Extremely high in energy and temperature.
Matter becomes so hot that the electrons separate from the nucleus.
Plasma is rare on earth (ex. lightning & parts of flames), but is the most common form of matter in the universe because….
Stars are made of plasma and stars are quite common.
NOTE: Plasma TV’s ARE NOT made of Plasma!!!!

8. Section 1 – More About Gases
2 scientists studied how gases behave in relation to pressure and temperature.
Boyle’s Law – pressure & volume are inversely (indirectly) related
The higher the pressure, the lower the volume.
The lower the pressure, the higher the volume
Charles’ Law – temperature & volume are directly related
The higher the temperature, the higher the volume
The lower the temperature, the lower the volume

9. Section 1 – Gas Laws
Boyle’s Law – pressure & volume are inversely (indirectly) related
P1 = V2
P2 V1
Charles’ Law – temperature & volume are directly related
V1 = V2
T1 T2

10. Section 1 – Using the Gas Laws
If 50 mL of oxygen gas is compressed from 20 atm of pressure to 40 atm of pressure, what is the new volume? (assume constant temp)
GIVEN:
V1 = 50 mL
V2=?
P1 = 20 atm
P2 = 40 atm
WORK:
P1 = V2
P2 V1
20 atm = V2
40 atm mL
1000 atm mL = 40 atm (V2)
40 atm atm
V2 = 25 mL

11. Section 1 - Using the Gas Laws
A gas occupies a volume of 100 mL at 300° C. At what temperature will the gas have a volume of 200 mL?
GIVEN:
V1 = 100 mL
V2= 200 mL
T1 = 300° C
T2 = ?
WORK:
V1 = V2
T1 T2
100 mL = 200 mL
300° C T2
100 mL (T2) = 60,000° C mL
100 mL mL
T2 = 600° C

12. Section 2 - Phase Changes
Phase changes are caused by adding or taking away thermal energy
Thermal energy is fancy schmancy word for HEAT!!!!!!
Phase changes of matter are called:
Melting
Freezing
Vaporization
Condensation
Sublimation

13. Section 2 - Phase Changes cont’d
Phase changes are Physical Changes
This is because the substance is changes its form, but it is not changing the kind of substance it is chemically.
Ex – water (H2O) is still water whether it is in an ice cube, liquid water or water vapor)

14. Section 2 - Solid – Liquid Phase Changes
Melting - Solid to Liquid
Melting point – temperature at which a substance will melt
Freezing – Liquid to Solid
Freezing Point – temperature at which a substance will freeze.
The melting point of a substance is the same temperature as its freezing point!!

15. Section 2 - Liquid - Gas Phase Changes
Vaporization – Liquid to Gas
2 kinds:
Evaporation – Liquid to Gas only at the surface of liquid
Boiling – Liquid to Gas in the entire liquid
Temperature at which a substance boils is the boiling point

16. Section 2 - Gas - Liquid Phase Changes
Condensation – Gas to Liquid
The gas molecules lose thermal energy (heat) and slow down. Then, as they come together, they join to form a liquid.

17. Section 2 - Solid - Gas Phase Changes
Sublimation – Solid directly to Gas
Examples
Solid carbon dioxide (dry ice) changes directly into a gas
Moth balls

18. As you move to the right, is heat being added to or given off by the substance?

19. As you move to the right, what is happening to the space between the molecules?

20. As you move to the left, is heat being added to or given off by the substance?

21. As you move to the left, what is happening to the space between the molecules?

22. What temperature is this if this substance is water?

23. What temperature is this if this substance is water?

24. Let’s Review for a Moment…
Phase of matter, color, shape, hardness, mass, volume, density were all what kind of properties of matter?
PHYSICAL PROPERTIES!!! Right……

25. Section 3 - Physical Properties - Definition
Physical Properties – properties of matter that can be observed using the senses without changing the identity of a substance.
What kind of property would describe a change of matter into another substance?

26. Section 3 - Chemical Properties and Changes
Chemical Properties – the properties that describe the ability of a substance to change into a different substance.
Flammability – the ability to burn
Ex wood is flammable
Supporting burning – the ability of a substance to be used during burning.
Ex – oxygen is needed for wood to burn but the oxygen itself doesn’t burn.

27. Section 3 - Chemical Properties and Changes
Chemical changes (aka chemical reaction) – the process by which a substance changes into another substance by chemical means.
Ex: cars rusting, wood burning, yeast changing sugar into gas in bread, cheese aging, leaves changing color…

28. Classify the following as either a physical or chemical change….
An ice cube cracking
Carving a piece of marble into a statue
Burning wood
Wax melting
Sugar dissolving in tea or coffee
Pop rocks releasing carbon dioxide into your mouth
Leaves changing colors in the fall