Classifying Matter

1
Classifying Matter
2
4.01 States of Matter

• Anything with mass that takes up space (volume)
  is matter.
• Exists in 4 states
• Solid
• Liquid
• Gas
• Plasma

3
4.01 States of Matter

• Solid
• The particles of a solid are in a tight, fixed
  position. Since the particles in solids are not
  free to move around they vibrate just a little.
  Solids have a set volume and a set shape.

4
4.01 States of Matter

• Liquid
• The particles of a liquid are close together, but
  they are not in a neat arrangement like in a
  solid. They have enough space to slide past each
  other. Liquids have a set volume but no set shape.

5
4.01 States of Matter

• Gas
• The particles of a gas have a lot of space
  between them. They move fast and in no order. The
  volume of gas also increases as temperature
  increases. Gasses have no set volume and no set
  shape.

6
4.01 States of Matter

• Plasma
• Contains particles that are positively and
  negatively charged. Atoms begin to lose
  electrons, creating charged particles that move
  freely. Plasma, like a gas, has no set volume or
  shape and can be found in stars, Plasma TVs, and
  neon signs.

7
4.01 States of Matter

• Kinetic Theory of Matter
• All matter is composed of tiny particles
• These particles are in constant, random motion
• The particles collide with each other and with
  the walls of any container in which they are held
• The amount of energy that the particles lose from
  these collisions is negligible.

8
4.01 States of Matter

• Kinetic Molecular Theory
• Explains why matter changes states
• Matter changes states due to gain or loss of
  energy
• Explains why a particular state behaves as it
  does
• Objects expand when heated
• Explains why the temperature of a substance
  increases as you heat it
• Temperature of an object is a measure of the
  average kinetic theory of a substance

9
4.01 States of Matter

• Heating Curves
• A graph of temperature vs. time for heating a
  substance

10
4.02 Classifying Matter

• Pure Substances
• Elements
• Element and atom are not the same
• Periodic Table of Elements
• Compounds
• Made from combined elements

11
(No Transcript)
12
4.02 Classifying Matter
13
4.02 Classifying Matter
Bromine (Br2) and Oxygen (O2) exist naturally as
molecules. Each molecule consists of two atoms
bonded together. Even though it is made of
molecules it is still an element because it
contains only one type of atom.
14
Element or Compound??
4.02 Classifying Matter

1. H20
2. Copper (Cu)
3. C6H12O6
4. NaCl
5. Oxygen (O2)
6. Sodium (Na)

15
4.02 Classifying Matter
Mixtures- Heterogeneous Mixtures
Homogeneous Mixtures- Solutions-
16
4.02 Classifying Matter
Classify the following as an element, compound,
or mixture. If mixture, make sure to label
homogenous or heterogeneous. 1) soda 4)
Nitrogen (N) 2) water (H20) 5) NH4 3) gravel
6) a taco
17
4.03 Properties of Matter

• Physical properties
• Physical properties are characteristics of a
  substance that can be measured without changing
  the identity of the substance.
• Appearance (for example, color or shape)
• Odor
• Melting point and boiling point
• Density
• Hardness
• Ductility and Malleability (ability to change
  shape)
• Solubility
• Electrical and thermal conductivity
• Magnetism

18
4.03 Properties of Matter

• Chemical properties
• characteristics of a substance that describe the
  ways it can react to form new materials.
• Chemical properties cannot be measured or studied
  without changing the composition of the
  substance.
• Flammability and other tendencies to react with
  oxygen
• Reaction with acids and bases
• Reaction with water
• Decomposition caused by light or heat
• Tendency to corrode

19
4.03 Properties of Matter

• Physical Changes
• Physical changes are changes that do not result
  in the formation of a new substance.
• The substance is still the same because chemical
  bonds have not been broken or formed, and so the
  atoms of the molecules are still connected in the
  same way.

20
4.03 Properties of Matter

• Chemical Changes
• referred to as chemical reactions.
• always produce new substances with properties
  that are typically very different from those of
  the reactants.
• some clues that can indicate a chemical change
  has occurred.
• visible flames
• color change
• bubbling or fizzing
• smoke
• heat or light given off
• formation of a substance in a different state
  (for example, a solid from two liquids)
• Of these observations, seeing flames is the only
  sign that always indicates a chemical change. All
  of the others can sometimes be the result of a
  physical change.

21
Event Physical Chemical
Cutting your hair
Mixing sugar and water
Baking soda reacts with baking soda and forms a gas
A piece of paper is crumpled up
Baking cookies
An aspirin is crushed into a powder
A tree burns to form ashes
Methanol is burned and leaves a residue
Water freezes to ice
A piece of metal is bent in half
22
4.03 Properties of Matter

• Law of Conservation of Mass
• Mass cannot be created or destroyed
• To put the law another way, the amount of matter
  before the change equals the amount of matter
  after the change.

23
4.03 Properties of Matter

• The law of conservation of mass is also true for
  physical changes. An ice cube has the same mass
  as the water produced when it melts.
• In other cases, conservation of mass is less
  obvious. If we think about it, we can usually
  explain cases in which the law of conservation of
  mass seems to have been violated.

24
Democritus (400 B.C.)
4.04 Atomic Theory

• Proposed that matter was composed of tiny
  indivisible particles
• Not based on experimental data
• Greek atomos

25
Alchemy (next 2000 years)
4.04 Atomic Theory

• Mixture of science and mysticism.
• Lab procedures were developed, but alchemists did
  not perform controlled experiments like true
  scientists.

26
John Dalton (1807)
4.04 Atomic Theory

• British Schoolteacher
• based his theory on others experimental data
• Billiard Ball Model
• atom is a uniform, solid sphere

27
John Dalton
4.04 Atomic Theory
Daltons Four Postulates
1. Elements are composed of small indivisible
particles called atoms. 2. Atoms of the same
element are identical. Atoms of different
elements are different. 3. Atoms of different
elements combine together in simple proportions
to create a compound. 4. In a chemical reaction,
atoms are rearranged, but not changed.
28
J. J. Thomson (1903)
4.04 Atomic Theory

• Cathode Ray Tube Experiments
• beam of negative particles
• Discovered Electrons
• negative particles within the atom
• Plum-pudding Model

29
J. J. Thomson (1903)
4.04 Atomic Theory

• Plum-pudding Model
• positive sphere (pudding) with negative
  electrons (plums) dispersed throughout

30
Ernest Rutherford (1911)
4.04 Atomic Theory

• Gold Foil Experiment
• Discovered the nucleus
• dense, positive charge in the center of the atom
• Nuclear Model

31
Ernest Rutherford (1911)
4.04 Atomic Theory

• Nuclear Model
• dense, positive nucleus surrounded by negative
  electrons

32
Niels Bohr (1913)
4.04 Atomic Theory

• Bright-Line Spectrum
• tried to explain presence of specific colors in
  hydrogens spectrum
• Energy Levels
• electrons can only exist in specific energy
  states
• Planetary Model

33
Niels Bohr (1913)
4.04 Atomic Theory
Bright-line spectrum

• Planetary Model
• electrons move in circular orbits within specific
  energy levels

34
Erwin Schrödinger (1926)
4.04 Atomic Theory

• Quantum mechanics
• electrons can only exist in specified energy
  states
• Electron cloud model
• orbital region around the nucleus where e- are
  likely to be found

35
Erwin Schrödinger (1926)
4.04 Atomic Theory

• Electron Cloud Model (orbital)
• dots represent probability of finding an e- not
  actual electrons

36
James Chadwick (1932)
4.04 Atomic Theory

• Discovered neutrons
• neutral particles in the nucleus of an atom
• Joliot-Curie Experiments
• based his theory on their experimental evidence

37
James Chadwick (1932)
4.04 Atomic Theory

• Neutron Model
• revision of Rutherfords Nuclear Model

38
An atom refresher
4.05 Properties of Atoms

• Matter is anything that takes up space and has
  mass.
• All matter is made of atoms
• Atoms are the building blocks of matter, sort of
  how bricks are the building blocks of houses.

39
An atom refresher
4.05 Properties of Atoms

• An atom has three parts
• Proton positive
• Neutron no charge
• Electron negative
• The proton neutron are found in the center of
  the atom, a place called the nucleus.
• The electrons orbit the nucleus.

Picture from http//education.jlab.org/qa/atom_mod
el_03.gif
40
What are elements?
4.05 Properties of Atoms

• Elements are the alphabet to the language of
  molecules.
• To make molecules, you must have elements.
• Elements are made of atoms. While the atoms may
  have different weights and organization, they are
  all built in the same way.

41
4.05 Properties of Atoms
42
More about Elements..
4.05 Properties of Atoms

• Elements are the building blocks of all matter.
• The periodic table is a list of all of the
  elements that can build matter. Its a little
  like the alphabet of chemistry.
• The periodic table tells us several things

43
4.05 Properties of Atoms
Atomic Number Number of protons and it is also
the number of electrons in an atom of an element.
8
O
Elements SymbolAn abbreviation for the element.
Oxygen
Elements Name
Atomic Mass/Weight Number of protons neutrons.
16
44
Atom Models
4.05 Properties of Atoms

• There are two models of the atoms we will be
  using in class.
• Bohr Model
• Lewis Dot Structure

45
Bohr Model
4.05 Properties of Atoms
-

• The Bohr Model shows all of the particles in the
  atom.
• In the center is circles. Each circle represents
  a single neutron or proton. Protons should have a
  plus or P written on them. Neutrons should be
  blank or have an N.
• In a circle around the nucleus are the electrons.
  Electrons should have a minus sign or an e.

-
46
Electrons have special rules.
4.05 Properties of Atoms

• You cant just shove all of the electrons into
  the first orbit of an electron.
• Electrons live in something called shells or
  energy levels.
• Only so many can be in any certain shell.

47
4.05 Properties of Atoms
Nucleus
1st shell
2nd shell
3rd shell
Adapted from http//www.sciencespot.net/Media/atom
sfam.pdf
48
Electrons have special rules.
4.05 Properties of Atoms

• You cant just shove all of the electrons into
  the first orbit of an electron.
• Electrons live in something called shells or
  energy levels.
• Only so many can be in any certain shell.
• The electrons in the outer most shell of any
  element are called valance electrons.

49
So lets try it.

3 Li Lithium 7
50
So lets try it.
Protons 3

3 Li Lithium 7
-



-
-
Electrons 3 2 in the 1st shell, 1 in the 2nd
shell
Neutrons 4 (7-34)
51
Lewis Dot Structure
4.05 Properties of Atoms

• The Lewis Dot Structure is a bit different from
  the Bohr model.
• It only shows the element symbol and its outer
  most electron shell.

O




52
How to
4.05 Properties of Atoms

1. Write the symbol.
2. Start on the right hand side, working your way
   clockwise around the symbol.
3. Try Lithium

53
4.06 The Periodic Table of Elements

• 1869, Dmitri Mendeleev, a Russian chemist, set
  out to organize the 63 known elements.
• He started by organizing the elements by their
  mass in ascending order.
• When elements were arranged in order of their
  mass, he noticed that their physical properties
  repeated

54
4.06 The Periodic Table of Elements

• To group elements by similar properties,
  Mendeleev had to arrange a few elements out of
  order by mass.
• the periodic trends did not fit perfectly with
  the elements masses.
• When atomic numbers became known, scientists
  organized the chart of elements using the number
  of protons in each element instead of the atomic
  mass.

55
4.06 The Periodic Table of Elements
The modern periodic table of elements is a
valuable resource. Check out the wealth of
information contained in the periodic table
56
4.06 The Periodic Table of Elements

• Element name and symbol
• Atomic number (number of protons in each atom)
• Average atomic mass

57
4.06 The Periodic Table of Elements

• Physical Properties metal, non-metal, or
  metalloid

58
4.06 The Periodic Table of Elements

• Electronegativity ability to attract electrons
• Bigger the number, the greater the ability to
  attract electrons and bond to other atoms
• Increases as you go left to right and move up

59
4.06 The Periodic Table of Elements

• Ionization Energy energy needed to release an
  electron
• Think, opposite of electronegativity
• Increases as you go left to right and up

60
4.06 The Periodic Table of Elements

• Atomic Radius
• Relates to number of energy levels quantum
  number
• Increases as you go down and to the left

61
4.06 The Periodic Table of Elements

• Valence Electrons outermost electrons
• Elements in the same group have similar valence
  electrons

62
4.06 The Periodic Table of Elements

• Oxidation Number number of electrons the atom
  uses or receives
• when atom loses electrons, - when atom gains
  electrons

63
4.06 The Periodic Table of Elements

• Representative Elements
• Columns 1-2 and 13-18
• Follow trends and behave more predicatibly than
  other groups

64
4.06 The Periodic Table of Elements

• Exceptions to the Rules
• Hydrogen
• Placed with metals even though it is a gas
• Placed in 1st column to reflect the properties of
  its electrons