1. Ch. 2 - Matter and Change
2.1 Properties of Matter 1

2. Recall…
From ch. 1…
Matter – anything with mass & volume (e.g., air; non-e.g., heat)
Understanding matter begins with observing properties. 2

3. Describing Matter “Types” of properties: Extensive *or* Intensive
depends upon amount (mass, volume)
*or*
Intensive
depends upon type of matter
(hardness, color, density) 3

4. Identifying Substances
AND
Physical Property
observed without changing the composition
*or*
Chemical Property (pg. 53)
observed when matter changes its composition; reactivity 4

5. Identifying Substances
matter with uniform & definite composition; “pure”
“Since a substance has identical composition, every sample has identical intensive properties.” 5

6. States of Matter
Three states of matter
Solid, liquid, gas 6

7. Indefinite shape Indefinite volume Indefinite shape Definite volume7

8. States of Matter Solid Definite shape & definite volume;
a solid is its own container
Particles tightly packed; orderly
Rigid; nearly incompressible
Expand slightly when heated 8

9. States of Matter Liquid Indefinite shape, definite volume;
takes on shape of container
Particles close together; free to move
Not rigid; Almost incompressible
Expand slightly when heated 9

10. States of Matter Gas Indefinite shape and indefinite volume
takes shape and volume of container
Particles very far apart; mostly “empty space”
Easily compressible 10

11. States of Matter Vapor o 27 C
The gaseous state of a substance that normally exists as a solid or liquid. o
27 C 11

12. Physical Changes Reversible (Irreversible)
Physical changes do not change the composition (identity) of matter.
Reversible (Irreversible)
The change can “undone”
Able to retrieve original sample 12

13. Physical Changes Most physical changes involve
a change in temperature.
Increase temperature, particles
move faster (more kinetic energy). 13

14. 2.2 Classifying Mixtures Mixture – a physical blend of 2+ substances
For example:
Air = nitrogen + oxygen + carbon dioxide + argon
A substance has fixed composition; the composition of a mixture varies. 14

15. Classifying Mixtures Phase – any distinct part within a mixture.
Two types of mixtures:
1. Heterogeneous – a mixture that is not uniform in its composition; 2+ phases
2. Homogeneous – a mixture with uniform composition throughout; single phase 15

16. Separating Mixtures
Physical properties can be used to separate mixtures.
Filtration – separating a solid from a liquid in a heterogeneous mixture
Distillation – separating the components of a liquid homogeneous mixture by their boiling points
Chromatography – separating a mixture based on a differences in solubility 16

17. Distillation
Filtration
Chromotography 17

18. 2.3 Elements & Compounds
Substances are classified as element or compound.
Element – simplest form of matter that has unique properties.
Hydrogen = H
carbon = C
oxygen = O
sodium = Na
chlorine = Cl
etc… 18

19. 2.3 Elements & Compounds
Compound – a substance composed of 2+ elements chemically combined in fixed proportion.
Water = H2O
table salt = NaCl
carbon dioxide = CO2
sucrose = C12H22O11
Compounds can only be broken down into simpler substances by chemical means. There is no chemical process that will break elements down into simpler substances. 19

20. Properties of Compounds
Compounds have different properties than the elements that make them up.
SODIUM
SODIUM CHLORINE = CHLORIDE
soft, silvery metal; yellow/green gas; white crystal;
reacts w/ water; reacts with ammonia; seasoning &
poisonous poisonous preserves food 20

21. Properties of Compounds
Compounds have different properties than the elements that make them up.
SODIUM
SODIUM CHLORINE = CHLORIDE
soft, silvery metal; yellow/green gas; white crystal;
reacts w/ water; reacts with ammonia; seasoning &
poisonous poisonous preserves food 21

22. Water  Hydrogen + Oxygen
Breaking Down Compounds
Chemical Change – a change in the composition of matter; indicated as an arrow:
Sugar  Carbon + Water
Water  Hydrogen + Oxygen
Chemical Change
COMPOUND ELEMENT COMPOUND
Chemical Change
COMPOUND ELEMENT ELEMENT 22

23. ELECTROLYSIS OF WATER: H2O Hydrogen + Oxygen
“to break” 23

24. Fig. 2.11
separated physically
separated
chemically 24

25. Symbols & Formulas
Chemists use chemical symbols to represent elements, and chemical formulas to represent compounds.
For example:
symbol: sodium = Na hydrogen = H
chlorine = Cl oxygen = O
formula: salt = NaCl water = H2O 25

26. 2.4 Chemical Changes Chemical Property
ability to undergo a chemical change; “reactivity”; “behavior”
observed when matter changes its composition
can be used to identify matter
e.g., burn, rot, rust, decompose, ferment, explode, corrode, oxidize, etc… 26

27. 2.4 Chemical Changes Chemical Change
change in the composition of matter
a.k.a. chemical reaction
REACTANT(S)  PRODUCT(S)
starting material finishing material;
“new” substance 27

28. Recognizing Chemical Changes
Possible “clues” to a chemical change:
Transfer of energy (i.e. light &/or heat given off)
Change in color
Production of gas
Formation of precipitate (a solid that forms out of a liquid)
Clues do not necessarily confirm chemical change. 28

29. Conservation of Mass The Law of Conservation of Mass
Mass is neither created nor destroyed in any chemical reaction.
Mass of reactants = mass of products 29

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