Download Physical or Chemical Property?

• 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.
• What is an atom?
• Atom: the smallest unit of matter that
retains the identity of the substance
Three Laws Supporting the
existence of Atoms
• Law of definite proportions – states that a
chemical compound always contains the same
elements in exactly the same proportions by
weight or mass
• Law of multiple proportions – states that
when two elements combine to form two or
more compounds, the mass of one element that
combines with a given mass of the other is in
the ratio of small whole numbers
• Law of conservation of mass – states that
mass cannot be created or destroyed in
ordinary chemical and physical changes
Dalton’s Theory
1. All matter is composed of extremely small
particles called atoms, which cannot be
subdivided, created, or destroyed.
2. Atoms of a given element are identical in
their physical and chemical properties.
3. Atoms of different elements differ in their
physical and chemical properties.
4. Atoms of different elements combine in
simple, whole-number ratios to form
compounds.
5. In chemical reactions, atoms are
combined, separated, or rearranged but
never created, destroyed, or changed.
Discovery of the Subatomic
Particles
• Electrons – Discovered using
Cathode Rays by English
Physicist J.J. Thomson.
• Nucleus – Discovered by
Ernest Rutherford using Goldfoil experiment
Atomic Structure
• Atoms are composed of 2 regions:
Nucleus: the center of the atom that
contains the mass of the atom
Electron cloud: region that surrounds
the nucleus that contains most of the
space in the atom
Electron
Cloud
Nucleus
What’s in the Nucleus?
• The nucleus contains 2 of the 3
subatomic particles:
Protons: positively charged
subatomic particles
Neutrons: neutrally charged
subatomic particles
What’s in the Electron
Cloud?
• The 3rd subatomic particle
resides outside of the nucleus
in the electron cloud
Electron: the subatomic particle
with a negative charge and
relatively no mass
How do these particles
interact?
• Protons and neutrons live
compacted in the tiny positively
charged nucleus accounting for
most of the mass of the atom
• The negatively charged electrons
are small and have a relatively
small mass but occupy a large
volume of space outside the
nucleus
How do the subatomic
particles balance each
other?
In an atom:
The protons = the electrons
• If 20 protons are present in an
atom then 20 electrons are there
to balance the overall charge of
the atom—atoms are neutral
The neutrons have no charge;
therefore they do not have to equal
the number of protons or electrons
Periodic Table
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
15.999
How do we know the number of
subatomic particles in an atom?
• Atomic number: this number
indicates the number of protons in an
atom
 Ex: Hydrogen’s atomic number is 1
• So hydrogen has 1 proton
 Ex: Carbon’s atomic number is 6
• So carbon has 6 protons
**The number of protons identifies the
atom. Ex. 2 protons = He, 29 protons = Cu
Learning Check
State the number of protons in each.
1. A nitrogen atom
A. 5 protons
B. 7 protons
C. 14 protons
1. A sulfur atom
A. 32 protons
B. 16 protons
C. 6 protons
12
How do we know the number
of subatomic particles in an
atom?
• Mass number: the number of
protons and neutrons in the
nucleus
Ex: hydrogen can have a mass of 3.
Since it has 1 proton it must have 2
neutrons
# of neutrons = mass # - atomic #
Determining the number of
protons and neutrons
Li has a mass number of 7 and an
atomic number of 3
Protons = 3 (same as atomic #)
Neutrons= 7-3 = 4 (mass # - atomic #)
• Ne has a mass number of 20 and an
atomic number of 10
Protons =
Neutrons =
What about the electrons?
• The electrons are equal to the
number of protons
So e- = p = atomic #
• Ex: He has a mass # of 4 and an
atomic # of 2
p+ = 2
no = 2
e- = 2
Determine the number of
subatomic particles in the
following:
• Cl has a mass # of 35 and an
atomic # of 17
p+ =
no =
e- =
• K has a mass # of 39 and an
atomic # of 19
P+ =
no =
e- =
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
Element
Name
Atomic
Number
Number of Number of
Protons
Neutrons
45
24
Mass
Number
80
52
89
silver
152
107
76
114
States of Matter
• The Kinetic Theory
1. All matter is composed of
small particles (atoms,
molecules, or ions).
2. They are in constant, random
motion.
3. They constantly collide
with each other and with the
walls of their container.
Phase
Liquid
Proximity
close
close
Gas
far apart
Solid
Particle Properties
Volume
Energy
little
definite
moderate
definite
a lot
indefinite
Shape
definite
indefinite
indefinite
What is a Physical Change?
• A physical change alters the form of a
substance, but does not change it to
another substance.
Example:
Making Orange Juice
What is a Chemical Change?
• When a substance undergoes a chemical
change, it is changed into a different
substance with different properties.
Example:
Baking a Cake
5 Signs of a Chemical Change
1. Color Change
2. Precipitation
Precipitation – the solid that forms from a
solution during a chemical reaction.
It looks like a cloudy solid in an otherwise clear
solution.
5 Signs of a Chemical Change
3. Gas Production
4. Temperature Change
5. Changes in Characteristic Properties (odor,
light given off)
Chemical or Physical Change?
• Cutting paper?
• Physical
Chemical or Physical Change?
• Ice melting?
• Physical
Chemical or Physical Change?
• Toast burning?
• Chemical
Chemical or Physical Change?
• Rocket fuel burning?
• Chemical
Chemical or Physical Change?
• Sawing wood?
• Physical
Chemical or Physical Change?
• Metal rusting?
• Chemical
Chemical or Physical Change?
• Disappearing puddle?
• Physical
Chemical or Physical Change?
• Candle burning?
• Chemical
Chemical or Physical Change?
• Dry ice?
• Physical
Physical or Chemical Property?
• Ability of gun
powder and fire
to explode.
Chemical
Property
Physical or Chemical Property?
• The color of a sunset.
Physical
Property
Physical or Chemical Property?
• The ability of a nail
to rust.
Chemical
Property
Physical or Chemical Property?
• The shape of a leaf.
Physical
Property
Physical or Chemical Property?
• The ability of wood
to burn.
Chemical
Property
Physical or Chemical Property?
• The hardness of a
diamond.
Physical
Property
Physical or Chemical Property?
• The volume of your
coke.
Physical
Property
Physical or Chemical Property?
• The mass of two camels.
Physical
Property
Physical or Chemical
Change?
• Water evaporates
from the ocean.
Physical or Chemical Change?
• The yolk of an egg,
which contains sulfur,
causes tarnish to form
on silver.
Physical or Chemical
Change?
• The ice on a lake melts
to become water in the
lake.
Physical or Chemical
Change?
• Charcoal in a fire turns
to ash after several
hours.
Physical or Chemical
Change?
• A pencil is sharpened
in a pencil sharpener,
leaving behind
shavings.
Physical or Chemical
Change?
• A battery makes
electricity to turn on a
flashlight.
Physical or Chemical Change?
• A bicycle rusts when left in the rain.
Physical or Chemical Change?
• A shirt is accidentally
torn in the washing
machine.
Physical or Chemical Change?
• A log is split in two by
an axe.
Properties - Pure Substances
Matter can either be found in nature as
a pure substance or a mixture.
• Pure
substance - a substance that contains
a single type of matter. When the substance
is pure, it has a unique set of properties
 Example: pure water contains ONLY molecules of
water (H2O) and NOTHING else!!
Properties of Matter - Mixtures
• Mixture - two or more substances mixed
together, but not chemically combined. Each
component in a mixture keeps its individual
properties.
 Example: salt water contains water molecules (H2O) and
sodium chloride (NaCl) molecules.
 The mixture will behave differently than the two materials
separate. Salt water will have a different boiling point
than pure water!
Types of Mixtures:
The prefix “homo” – indicate sameness
Homogeneous – A
homogeneous mixture has the
same uniform appearance
throughout. Many
homogeneous mixtures are
commonly referred to as
solutions.
The prefix “hetero” – indicate difference
Heterogeneous - A
heterogeneous mixture
consists of visibly different
substances or phases. The
three phases or states of
matter are gas, liquid, and
solid.
YES
Uniform properties?
If not, it’s a
heterogeneous
mixture
YES
Fixed composition?
Can be broken down
chemically?
If not, it’s a
homogeneous mixture
If not, it’s an element
If so it’s a compound
What is it?
Homogeneous
Cheerios
What is it?
Homogeneous
Kool - Aid
What is it?
Heterogeneous
Trail Mix
What is it?
Homogeneous
Water
What is it?
Heterogeneous
Italian Salad Dressing
What is it?
Heterogeneous
Raisin Bran
What is it?
Homogeneous
White Vinegar
An element is a substance that is made
from one kind of atom only. It cannot
be broken down into simpler substances.
atom
An element
atom
An element
A compound is a substance that is made
from more than one element.
atom
A compound made up of
2 different elements
atom
A compound made up of
7 different elements
A compound can be broken down into
elements
An element
An element
A compound made up of 3
different elements
An element
Material
Made up of:
Water
Hydrogen and
Oxygen
Carbon
Coal
Carbon
dioxide
Oxygen
Carbon and Oxygen
Chalk
Calcium, Carbon &
Oxygen
Sodium & Chlorine
Table salt
Caffeine
Oxygen
Carbon, Hydrogen,
Nitrogen & Oxygen
Element or
compound