Transcript Matter and Energy

Matter And
Energy
Chemistry I: Chapter 2a
Chemistry I Honors:
Chapter 2
ICP: Chapter 15 & 16a
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The Nature of Matter
Gold
Mercury
Chemists are interested in the nature of matter
and how this is related to its atoms and
molecules.
Chemistry & Matter
• We can explore the
MACROSCOPIC world — what we
can see —
• to understand the PARTICULATE
worlds we cannot see.
• We write SYMBOLS to describe
these worlds.
A Chemist’s View of
Water
Macroscopic
H 2O
(gas, liquid, solid)
Particulate
Symbolic
A Chemist’s View
Macroscopic
Particulate
2 H2(g) + O2 (g)
--> 2 H2O(g)
Symbolic
Kinetic Nature of Matter
Matter consists of atoms
and molecules in _____.
STATES OF MATTER
• _______ — have rigid shape, fixed
volume. External shape can reflect the
atomic and molecular arrangement.
–Reasonably well understood.
• _______ — have no fixed shape and
may not fill a container completely.
–Not well understood.
• _______ — expand to fill their
container.
–Good theoretical understanding.
OTHER STATES OF
MATTER
• PLASMA — an electrically charged
gas; Example: the sun or any other star
• BOSE-EINSTEIN CONDENSATE
— a condensate that forms near
absolute zero that has
superconductive properties; Example:
supercooled Rb gas
Physical
Properties
What are some physical
properties?
• color
• melting and boiling point
• Odor
• Anything you can touch,
see, hear, taste…
Extensive vs. intensive
property
• Extensive properties are dependent upon the
amount of substance present. Ex- mass,
length
• Intensive property is independent of the
amount of substance present. Ex- density,
temperature
Graphite —
layer
structure of
carbon
atoms
reflects
physical
properties.
Physical Changes
– can be observed without
changing the identity of
the substance
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.
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.
Sure Signs of a Chemical
Change
• Heat
• Light
• Gas Produced (not
from boiling!)
• Precipitate – a solid
formed by mixing
two liquids together
• Law of conservation
of mass- Matter is
neither created nor
destroyed during a
chemical reaction.
Physical vs. Chemical
• Examples:
– melting point
physical
– flammable
chemical
– density
physical
– magnetic
physical
– tarnishes in air
chemical
Physical vs. Chemical
•
Examples:
– rusting iron
– dissolving in water
– burning a log
– melting ice
– grinding spices
Matter Flowchart
MATTER
yes
MIXTURE
yes
Is the composition
uniform?
Homogeneous
Mixture
(solution)
PURE SUBSTANCE
no
Heterogeneous
Mixture
Colloids
no
Can it be physically
separated?
yes
Can it be chemically
decomposed?
Compound
Suspensions
no
Element
Types of Mixtures
• Variable combination of 2 or more
pure substances.
Heterogeneous –
visibly separate phases
Homogeneous –
Same throughout
Methods of separation
• Filtration- use filter paper to separate based
on particle size
• Distillation- boil off liquids at different
temperatures
• Crystallization- separate based on formation
of crystals
• Sublimation- solids going directly to
gases.opposite- deposition.
• Chromatography- liquids rise up in a column
based on affinity
• Do Chromatography lab
Practice
1. Which of the following is NOT matter? (1) a chair (2) air
(3) light (4) water
2. Which of the following is NOT a property of matter? (1)
inertia (2)occupies space (3) composed of elements (4)
weightlessness
3. Which of the following may be heterogeneous? (1)
elements only (2) compounds only (3) mixtures only (4)
elements and compounds
4. Which of the following is pure? (1) elements only (2)
compounds only (3) mixtures only (4) elements and
compounds
5. Which of the following consists of more than one
substance?
(1) elements only (2) compounds only (3) mixtures only
• (4) elements and compounds
Practice (contd).
6. Which of the following are types of matter? (1) elements
only (2) compounds only (3) mixtures only (4) all of these
7. Which of the following is a type of mixture? (1) elements
only(2) compounds only (3) solutions only (4) elements
and Compounds
8. Which of the following is NOT composed of two or more
types of atoms? (1) element (2) compound (3) solution (4)
mechanical mixture
9. Which represents a homogeneous mixture? (1) CuSO4(s)
(2) NaCl(aq) (3) Br2(R) (4) CO2(g)
10. Which substance can be decomposed by a chemical
change?
(1) ammonia (2) iron (3) argon (4) helium
Elements and compounds
• Elements- simplest form of matter
• Compounds formed by combining elements in a fixed
ratio.
• Periodic table- organizes elements into groups
(families) and periods.
• Groups are vertical and periods are horizontal
• Law of definite proportions- Any compound is always
composed of same elements in same proportion.
• Ex- CuF2= 1 Cu 2F
• Percent by mass=mass of element/ mass of compound
x100.
• P88 Practice problems- q19-22
Law of multiple proportions
• Compounds can be formed in more than one
way between two or more elements.
• Elements can combine in different
proportions with whole number ratios when
this happens.
• Ex- H2O and H2O2