Matter and Change

1
Matter and Change

• Chapter 1

2
Branches of Chemistry

• Organic Chemistry
• Inorganic Chemistry
• Physical Chemistry
• Analytical Chemistry
• Biochemistry
• Theoretical Chemistry
• .and many more!

3
Matter
anything that has mass and takes up space

• pure substances compounds and elements

mixtures two or more pure substances mixed in
the same containernot bonded
4
Pure Substances

• Element A pure substance made of only one kind
  of atom
• Atom An atom is the smallest unit of an
  element that maintains the properties of that
  element

5
Pure Substances

• Compound A substance that is made from the
  atoms of two or more elements that are
  chemically bonded.
• Molecule the smallest unit of an element
  or compound that retains all of the properties
  of that element or compound

6
Huh?

• How can a molecule describe an element?

7
Diatomic Elements

• H2, Br2,O2, F2, I2, N2, Cl2,

Uncle Henry BrOFINCl
These elements are found as a pair, chemically
bonded to one another. They are not always in
pairs in a compound but are in pairs when they
are found as the pure element. Ex H2O (only 1
oxygen)
8
Compounds and Elements
compound
element
element
compound
compound
9
space filling model
molecular model
chemical formula
structural formula
10

• SHAPE
• definite shape
• indefinite shape
• indefinite shape

• VOLUME
• definite volume
• definite volume
• indefinite volume

• Solid
• Liquid
• Gas

11
States of Matter

• The particles of a solid are packed together in
  relatively fixed positions.
• The particles have strong attractive forces and
  low energy.
• (s)

12
Solids

• Solids are in a relatively fixed position.
• Solids have only vibrational movements around
  fixed points.
• Solids have definite shape and volume.
• Solids are almost incompressible.
• Solids do not diffuse (practically).

13
Solids

• Solids are either crystalline or amorphous.
• crystalline consist of crystals, particles
  arranged in an orderly, geometric repeating
  pattern
• amorphous Greek for without shape consist of
  particles, randomly arranged

14
Crystalline Solids
NaCl is cubic.

• Crystalline solids break into orderly pieces.
  After breaking salt, the cubic structure is still
  visible.

15
Crystalline Solids

• crystal structure three-dimensional arrangement
  of particles of a crystal, represented by a
  lattice
• unit cell The smallest portion of a crystal
  lattice that shows the 3-D pattern

16
Crystalline Systems
17
Amorphous Solids
Amorphous solids break into random pieces. They
usually shatter into irregular shapes.
Most plastics are amorphous.
18
Amorphous Solids

• The freezing point of amorphous solids can vary
  according to how slowly the material cools. (Ex
  butter)
• http//math.ucr.edu/home/baez/physics/General/Glas
  s/glass.html

19
States of Matter

• The particles of a liquid are close together but
  can most past one another.
• These particles have more energy than those of a
  solid, and this energy is what allows a liquid to
  flow.
• Pure liquid (l)
• A liquid solution (aq)

20
Liquids

• LIQUIDS
• have a definite volume and take on the shape of
  their container (unlike gases)
• have a high density
• are not compressed well (brake fluid)
• diffuse (like food coloring in water)
• have surface tension
• are fluids (but fluid ¹ liquid)

21
Liquids

• surface tension a force that tends to pull
  adjacent parts of a liquids surface together,
  thereby decreasing surface area to the smallest
  possible size.
• Surface tension results from attractive forces
  between the particles in the liquid. The
  stronger the attractive force, the higher the
  surface tension.

22
Liquids
Notice that the pull on the mercury atoms at
the top is not symmetrical. That is what gives
the characteristic spherical shape to drops of
liquid.
23
Liquids

• viscosity the resistance of a liquid to flow
• high viscosity thick liquid
• low viscosity thin liquid
• Liquids with stronger intermolecular forces have
  higher viscosity.
• An increase in temperature will decrease the
  viscosity.

24
Liquids

• volatile liquid - a liquid that evaporates
  readily at low temperatures
• The higher the volatility of a liquid, the weaker
  the intermolecular forces of attraction between
  their particles.
• An increase in T will increase evaporation.

25
Liquids
In each cylinder, can you describe which forces
are greater cohesive or adhesive?

• cohesive forces
• forces of attraction between like molecules (H2O
  to H2O)
• adhesive forces
• forces of attraction between unlike molecules
  (H2O to glass)

26
Liquids

• capillary action - the attraction of the surface
  of a liquid to the surface of a solid (adhesive
  forces)
• Many liquids will creep along a solid, like
  water does to paper or cloth fibers until the
  pull of gravity is too much for it to overcome.

27
States of Matter

• The particles of a gas move rapidly past one
  another, and are at a great distance apart from
  one another compared to their size.
• These particles have very high energy.
• (g)

28
States of Matter - Plasma

• A plasma is a very high temperature physical
  state of matter in which atoms lose their
  electrons.
• Plasma is found in fluorescent light bulbs and
  plasma Televisions.

29
Solid, Liquid, or Gas?
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
What happens during a phase change?
34
The Kinetic Theory of Heat and Temperature

• When a phase change is occurring, the temperature
  does not change, only the position of the
  particles. (PE)
• When something is being heated and it is not
  changing phase, the temperature will rise. (KE)

35
Potential Energy Differences
PE energy of position
36
PE vs. KE

• Only differences in kinetic energy are reflected
  by temperature differences.
• Difference in potential energy are NOT reflected
  in temperature differences.

THERE IS NO TEMPERATURE CHANGE DURING A PHASE
CHANGE.
37
Phase Changes

• During solidification or melting
• DH Kfm
• Kf heat of fusion, the amount of heat needed to
  melt/freeze 1g of a substance

• During boiling or condensing
• DH Kvm
• Kv heat of vaporization, the amount of heat
  needed to boil/condense 1g of a substance

38
Phase Changes

• Kf for water 333 J/g
• Kv for water 2260 J/g

39
Heating Curve for Water
40
Phase Diagrams
CRITICAL PRESSURE (the lowest pressure at which
the substance can still be a liquid at the
critical T)
CRITICAL POINT
TRIPLE POINT
CRITICAL TEMPERATURE (no more liquids
above this)
41
Phase Diagram for Water
42
What two phase changes are occurring at the same
time?
43
Physical Properties

• physical property a characteristic that can be
  observed or measured without changing the
  identity of the substance

state of matter
melting point
mass
color
44
Physical Changes

• physical change a change in a substance that
  does not involve a change in the identity of the
  substance

breaking
cutting
dissolving
tearing
boiling
45
All phase changes are physical changes.
46
Chemical Properties

• chemical property a characteristic that can be
  observed or measured with a change in the
  identity of the substance

flammability
reacts with an acid
reacts with oxygen
47
Chemical Changes

• chemical change a change in a substance that
  does involve a change in the identity of the
  substance

color change
gas released (often with an odor)
energy change (light, heat, )
precipitate formed
four good indications of a chemical change.
48
Precipitate
aqueous dissolved in water

• precipitate a solid formed from two aqueous
  solutions during a chemical reaction

49
Extensive vs. Intensive Properties

• extensive DOES depend on the amount of matter
  present

Examples mass, volume, amount of energy within a
substance

• intensive does NOT depend on the amount of
  matter present

Examples color, melting point, density, luster
If mass and volume are extensive properties, why
is density an intensive property?
50
Classification of Matter
51
Decomposition of Water
water hydrogen oxygen
2H2O(l) 2H2(g) O2(g)


reactants
yield
products
52
Hoffman Apparatus

• The Hoffman Apparatus is used to decompose water
  into its pure elements. This is a chemical
  change. The new substances (hydrogen gas and
  oxygen gas) did not retain the properties of the
  original substance (water).
• Watch this video!

53
Homogeneous Mixtures

• the same throughouteach sample contains the same
  ratio of ingredients
• (Also called solutions)

Heterogeneous Mixtures
different throughouteach sample contains a
different ratio of ingredients
54
Separation of Mixtures
density

• PHYSICAL changes only

magnetism
by hand
evaporation
filtration
chromatography
55
Separation of elemental Fe
magnetism

• This doesnt work with iron that is bound into a
  compound, only with elemental Fe.

56
Distillation Apparatus
57
Mixture or Pure Substance?
58
Homogeneous Mixture, Heterogeneous Mixture or
Pure Substance?