1. Chapter 15 – Classification of Matter
Mark McKenzie
Newark HS
E201
Chem-Phys, Chapter 15
Page 1

2. Scientific Method
Chem-Phys, Chapter 15
Page 2

3. Pure Substances
A pure substance is a type of matter with a fixed composition.
Examples: water, salt, sugar
An element is a substance in which all atoms have the same identity.
Examples: gold, oxygen, aluminum
About 90 elements occur naturally, another 20 have been made by man.
Chem-Phys, Chapter 15
Page 3

4. Compounds
A compound is a substance in which the atoms of two or more elements are combined in a fixed proportion.
Examples:
Salt: ALWAYS 60.7% chlorine and
39.3% sodium
Water: ALWAYS 88.8% Oxygen
11.2% Hydrogen
Chem-Phys, Chapter 15
Page 4

5. Mixtures
A mixture is a material made up of two or more substances that can be easily separated by physical means.
There are two kinds of mixtures:
A heterogeneous mixture is a mixture in which different materials can be distinguished easily.
A homogeneous mixture contains two or more gaseous, liquid, or solid substances blended evenly throughout.
Chem-Phys, Chapter 15
Page 5

6. Examples of Mixtures Examples of Heterogeneous Mixtures:
A bag of m&m’s.
A mixture of sand and iron filings.
Concrete
Examples of Homogeneous Mixtures:
Coke (before the top is taken off)
Gasoline
Air
Plastic
Chem-Phys, Chapter 15
Page 6

7. Solutions
A solution is a homogeneous mixture of particles so small that they cannot be seen with a microscope and will never settle to the bottom of the container.
Chem-Phys, Chapter 15
Page 7

8. Colloids
A colloid is a type of mixture with particles that are larger than those in solutions but not heavy enough to settle out.
Examples:
Milk (droplets of fat seen under a microscope)
Fog
Smoke
Chem-Phys, Chapter 15
Page 8

9. Detecting Colloids
When light passes through a colloid, a small portion of the light is scattered by the particles in the colloid.
The scattering of light by a colloid is called the Tyndall effect.
Example:
Turn on bright lights in fog
Chem-Phys, Chapter 15
Page 9

10. Suspensions
A suspension is a heterogeneous mixture containing a liquid in which visible particles settle.
Examples:
Mississippi River water has silt which will settle out.
Some paint has particles of pigment which will settle out.
Stirring prevents a suspension from settling.
Chem-Phys, Chapter 15
Page 10

11. Solutions, Colloids, Suspensions
Description
Solution
Colloids
Suspensions
Settle upon standing? No
Yes
Separate using filter paper?
Particle size
0.1 to 1 nm
1-100 nm
> 100 nm
Scatter Light?
Chem-Phys, Chapter 15
Page 11

12. Chapter 15, Section 1 Review
Define substance.
Define mixture.
What is an element?
What is a compound?
Compare and contrast:
Solutions
Colloids
Suspensions
Chem-Phys, Chapter 15
Page 12

13. Physical Properties
A physical property is any characteristic of a material that you can observe without changing the identity of the substances that make up the material.
Examples:
Melting point - Height
Boiling point - Stretchiness
Color - Temperature
Weight - Volume
Chem-Phys, Chapter 15
Page 13

14. Physical Properties
Some physical properties can be determined by appearance:
Color
Physical state
Some physical properties can be determined by how something behaves:
A paperclip conducts electricity
A pin is attracted by a magnet
Gold can be pounded into a very thin sheet
Chem-Phys, Chapter 15
Page 14

15. Using Physical Properties to Separate
Separating by size: A mixture of poppy seeds and sunflower seeds can be separated by using a sieve.
Separating with magnetism: A mixture of sand and iron filings can be separated with a magnet.
Chem-Phys, Chapter 15
Page 15

16. Physical Change
A change in size, shape, or state of matter is a physical change.
In a physical change, no new substances are formed.
Examples:
Ice melts into water
Heating a iron rod until it is white hot
Water vapor condenses to make rain
Chem-Phys, Chapter 15
Page 16

17. Using Physical Change to Separate
Sea water can be vaporized and condensed to make pure water without salts or microorganisms.
Distillation is the process for separating substances in a mixture by evaporating a liquid and re-condensing its vapor.
Chem-Phys, Chapter 15
Page 17

18. Chemical Properties
A chemical property is a characteristic of a substance that indicates whether it can undergo a certain chemical change.
Examples:
Will it burn?
A match – yes.
Iron nail – no.
React with water?
A match – no.
Iron nail – yes (rust).
Chem-Phys, Chapter 15
Page 18

19. Evidence of a Chemical Change
Evolution of a Gas (Bubbles, Odor)
Formation of a Precipitate (Formation of Cloudiness in a Clear Solution, Solids Collecting at the Bottom or Top)
Release of Energy (Heat, Light)
Color Change
Chem-Phys, Chapter 15
Page 19

20. Using Chemical Change to Separate
Chemical change can be used to separate:
Silver tarnish (black silver sulfide) and be reacted with baking soda and aluminum foil. The resulting reaction releases silver metal and removes the sulfur.
Chem-Phys, Chapter 15
Page 20

21. Weathering: Chemical or Physical Change?
Physical change: When water freezes in cracks and breaks larger rocks into smaller rocks, that is a physical change.
Chemical change: Slightly acid water will dissolve the calcium carbonate in limestone. This is a chemical change.
Chem-Phys, Chapter 15
Page 21

22. Chemical Properties and Chemical Change
Burning hydrogen (H2) in oxygen (O2) gives H2O.
Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules.

23. Sure Signs of a Chemical Change
Heat
Light
Gas Produced (not from boiling!)
Precipitate – a solid formed by mixing two liquids together

24. Physical vs. Chemical physical Examples: melting point chemical
flammable
density
magnetic
tarnishes in air

25. Physical vs. Chemical Examples: rusting iron dissolving in water
burning a log
melting ice
grinding spices

26. Matter Flowchart MATTER yes no MIXTURE PURE SUBSTANCE no yes no yes
Can it be physically separated?
MIXTURE
PURE SUBSTANCE
Is the composition uniform? no
yes
Can it be chemically decomposed? no
yes
Homogeneous Mixture
(solution)
Heterogeneous Mixture
Compound
Element
Colloids
Suspensions

27. Types of Mixtures Variable combination of 2 or more pure substances.
Heterogeneous – visibly separate phases
Homogeneous – Same throughout

28. Conservation of Mass
The law of conservation of mass states that the mass of all substances that are present before a chemical changes equals the mass of all the substances that remain after the change.
Chem-Phys, Chapter 15
Page 28

29. Law of Conservation of Mass Example
If 18 grams of hydrogen react completely with 633 grams of chlorine to make hydrogen chloride, how many grams of hydrogen chloride are formed?
Answer: 18 g g = 651 grams of HCl
Chem-Phys, Chapter 15
Page 29

30. Chapter 15, Section 2 Review
How do you identify a substance using physical properties?
Compare and contrast physical and chemical changes.
Identify chemical changes.
What is the law of conservation of mass? How does it apply to chemical changes?
Chem-Phys, Chapter 15
Page 30

31. Identifying reactions
Chem-Phys, Chapter 15
Page 31

32. Chem-Phys, Chapter 15
Page 32

33. Chem-Phys, Chapter 15
Page 33

34. Chem-Phys, Chapter 15
Page 34