Download PS_Module 4 - Leon County Schools

Classifying Matter
4.01 – States of Matter
• Anything with mass that takes up space
(volume) is matter.
• Exists in 4 states
– Solid
– Liquid
– Gas
– Plasma
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.
4.01 – 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.
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.
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.
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.
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
4.01 – States of Matter
• Heating Curves
– A graph of temperature vs. time for heating a
substance
4.02 – Classifying Matter
Pure Substances
•Elements –
•Element and atom are not
the same
• Periodic Table of
Elements
•Compounds –
•Made from combined
elements
4.02 – Classifying Matter
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.
4.02 – Classifying Matter
Element or Compound??
1.
2.
3.
4.
5.
6.
H20
Copper (Cu)
C6H12O6
NaCl
Oxygen (O2)
Sodium (Na)
4.02 – Classifying Matter
MixturesHeterogeneous Mixtures –
Homogeneous MixturesSolutions-
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
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
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
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.
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.
Event
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
Physical
Chemical
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.
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.
4.04 – Atomic Theory
Democritus (400 B.C.)
• Proposed that matter was
composed of tiny indivisible
particles
• Not based on experimental
data
• Greek: atomos
4.04 – Atomic Theory
Alchemy (next 2000 years)
• Mixture of science and mysticism.
• Lab procedures were developed, but alchemists did not
perform controlled experiments like true scientists.
4.04 – Atomic Theory
John Dalton (1807)
• British Schoolteacher
– based his theory on others’
experimental data
• Billiard Ball Model
– atom is a
uniform,
solid sphere
4.04 – Atomic Theory
John Dalton
Dalton’s 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.
4.04 – Atomic Theory
J. J. Thomson (1903)
• Cathode Ray Tube
Experiments
– beam of negative particles
• Discovered Electrons
– negative particles within the
atom
• Plum-pudding Model
4.04 – Atomic Theory
J. J. Thomson (1903)
Plum-pudding Model
– positive sphere (pudding)
with
negative electrons
(plums) dispersed
throughout
4.04 – Atomic Theory
Ernest Rutherford (1911)
• Gold Foil Experiment
• Discovered the nucleus
– dense, positive charge in the
center of the atom
• Nuclear Model
4.04 – Atomic Theory
Ernest Rutherford (1911)
• Nuclear Model
– dense, positive nucleus surrounded by
negative electrons
4.04 – Atomic Theory
Niels Bohr (1913)
• Bright-Line Spectrum
– tried to explain presence of
specific colors in hydrogen’s
spectrum
• Energy Levels
– electrons can only exist in
specific energy states
• Planetary Model
4.04 – Atomic Theory
Niels Bohr (1913)
Bright-line spectrum
• Planetary Model
– electrons move in circular
orbits within specific energy
levels
4.04 – Atomic Theory
Erwin Schrödinger (1926)
• 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
4.04 – Atomic Theory
Erwin Schrödinger (1926)
Electron Cloud Model (orbital)
• dots represent probability of finding an enot actual electrons
4.04 – Atomic Theory
James Chadwick (1932)
• Discovered neutrons
– neutral particles in the
nucleus of an atom
• Joliot-Curie Experiments
– based his theory on their
experimental evidence
4.04 – Atomic Theory
James Chadwick (1932)
Neutron Model
• revision of Rutherford’s Nuclear Model
4.05 – Properties of Atoms
An atom refresher
• 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.
•
•
•
•
4.05 – Properties of Atoms
An atom refresher
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_model_03.gif
4.05 – Properties of Atoms
What are elements?
• 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.
4.05 – Properties of Atoms
4.05 – Properties of Atoms
More about Elements..
• Elements are the building
blocks of all matter.
• The periodic table is a list of all
of the elements that can build
matter. It’s a little like the
alphabet of chemistry.
• The periodic table tells us
several things…
4.05 – Properties of Atoms
Atomic Number:
Number of protons and it is also the
number of electrons in an atom of an
element.
Element’s Symbol:
An abbreviation for the element.
Elements Name
Atomic Mass/Weight:
Number of protons + neutrons.
8
O
Oxygen
16
4.05 – Properties of Atoms
Atom Models
• There are two models of the atoms we will be
using in class.
• Bohr Model
• Lewis Dot Structure
4.05 – Properties of Atoms
Bohr Model
• 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.
-
+
+
-
4.05 – Properties of Atoms
Electrons have special rules….
• You can’t 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.
4.05 – Properties of Atoms
Nucleus
1st shell
2nd shell
3rd shell
Adapted from http://www.sciencespot.net/Media/atomsfam.pdf
4.05 – Properties of Atoms
Electrons have special rules….
• You can’t 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.
So let’s try it….
3
Li
Lithium
7
So let’s try it….
Protons = 3
3
-
+
+
Li
+
-
Lithium
-
7
Electrons = 3
2 in the
1st
shell, 1 in the
2nd
shell
Neutrons = 4
(7-3=4)
4.05 – Properties of Atoms
-
Lewis Dot Structure
• The Lewis Dot Structure
is a bit different from
the Bohr model.
• It only shows the
element symbol and it’s
outer most electron
shell.
-
-
+
+ + +
-
-
+ + +
+
-
-
•
• O ••
••
-
4.05 – Properties of Atoms
How to…
1. Write the symbol.
2. Start on the right
hand side, working
your way clockwise
around the symbol.
3. Try Lithium
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
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.
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:
4.06 – The Periodic Table of Elements
•Element name and symbol
•Atomic number (number of protons in
each atom)
•Average atomic mass
4.06 – The Periodic Table of Elements
•Physical Properties: metal, non-metal, or
metalloid
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
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
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
4.06 – The Periodic Table of Elements
•Valence Electrons – outermost electrons
•Elements in the same group have similar
valence electrons
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
4.06 – The Periodic Table of Elements
•Representative Elements
•Columns 1-2 and 13-18
•Follow trends and behave more
predicatibly than other groups
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