1. Matter
Chemistry I: Chapter 2

2. What is Chemistry?
Textbook Definition: The science of matter and the changes it undergoes.
Dictionary Definition: The science of the composition, structure, properties, and reactions of matter, especially of atomic and molecular systems.

3. Chemistry “The central science” – Why?
Because most of the phenomena that occur in the world involve chemical changes

4. What is Matter? The material of the universe has mass and volume
mass: the amount of matter in an object
volume: the amount of space an object takes up

5. The Nature of Matter Gold Mercury
Chemists are interested in the nature of matter and how this is related to its atoms and molecules.

6. Chemistry & Matter
We can explore the MACROSCOPIC world — what we can see —
to understand the PARTICULATE (MICROSCOPIC) worlds we cannot see.
We write SYMBOLS to describe these worlds.

7. A Chemist’s View of Water
Macroscopic
H2O
(gas, liquid, solid)
Symbolic
Particulate

8. A Chemist’s View Macroscopic 2 H2(g) + O2 (g) --> 2 H2O(g)
Particulate
Symbolic

9. The Macroscopic View
The states of matter:
Solids
Liquids
Gases
Plasma

10. Kinetic Nature of Matter
Matter consists of atoms and molecules in constant random motion.

11. STATES OF MATTER
Solids — have rigid shape, fixed volume. External shape can reflect the atomic and molecular arrangement.
Reasonably well understood.
Liquids — have no fixed shape and may not fill a container completely.
Not well understood.
Gases — expand to fill their container.
Good theoretical understanding.

12. OTHER STATES OF MATTER
PLASMA — an electrically charged gas; Example: the sun or any other star

13. Gas Liquid Solid low density high density fills container completely
does not expand to fill container - has definite volume
rigidly retains its volume
assumes shape of container
retains own shape

14. The Particulate Nature of Matter
All matter is made up of atoms
Elements consist of atoms of the same type
H, He, Cs, Ru, Fe, O
Compounds are formed when atoms chemically bond to one another in a specific way
CO, H2O, NaBr, C6H12O6

15. Properties of Matter Physical vs. Chemical Properties
physical property - characteristic of a substance that can be observed without changing the substance’s identity
chemical property - characteristic of a substance that can only be observed if the identity of the substance is changed

16. Physical Properties What are some physical properties? color
melting and boiling point
odor

17. Chemical Properties What are some chemical properties? Flammability
Reactivity with water
If it tarnishes

18. Physical vs. Chemical Properties
Examples:
melting point
flammable
density
magnetic
tarnishes in air

19. Changes of Matter Physical vs. Chemical Changes
physical change - change in one or more physical properties, but does not affect the composition of a substance
chemical change - change in the composition of a substance, in which a substance becomes a new substance (aka, a chemical reaction)

20. Physical Changes Some physical changes would be boiling of a liquid
melting of a solid
dissolving a solid in a liquid to give a homogeneous mixture — a SOLUTION.

21. Chemical Changes Some chemical changes would be
Hydrogen and oxygen combining to form water
Silver tarnishing
Baking a cake
Any chemical reaction!

22. Chemical Changes
Burning hydrogen (H2) in oxygen (O2) gives H2O.

23. Sure Signs of a Chemical Change
Heat
Light
Gas Produced (not from boiling!)
Precipitate – a solid formed by mixing two liquids together
CA/CCA0/MOVIES/S1047.MOV

24. Physical vs. Chemical Changes
Examples:
rusting iron
dissolving in water
burning a log
melting ice
grinding spices
chemical
physical

25. Classifying Matter
pure substances (elements and compounds); always have the same composition
mixtures (heterogeneous and homogeneous); composition varies; made up of 2 or more pure substances

26. How do you know what type of matter it is?
Pure substances
elements cannot be broken down into anything smaller than the representative atoms
compounds can be chemically separated (decomposed), using chemical reactions

27. How do you know what type of matter it is?
Mixtures: can be separated physically
homogeneous = “same throughout”; no visibly different parts; uniform; a solution
heterogeneous = contains regions with different properties; visibly different areas; doesn’t mix (not uniform)

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

29. Mixture Separation Techniques
filtration - separation of solid from a liquid using filter paper
only one for heterogeneous mixtures
parts already have to be in different states for filtration to work
distillation - depends on different boiling points of the substances in a solution

30. Mixture Separation Techniques
chromatography - separates parts of a solution using their different levels of attraction for a stationary substance
crystallization - boils off liquid to leave crystalized (solidified) substance that had been dissolved in the liquid

31. Matter Flowchart MATTER yes no no yes no yes
Can it be physically separated?
Is the composition uniform? no
yes
Can it be chemically decomposed? no
yes

32. 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