Download Matter - Dwight Public Schools

Matter
Anything that has mass & takes
up space
So matter is???
Maybe it is easier to ask
Democritus’s View
• Democritus (460 B.C. – 370 B.C.)
– Greek philosopher
– Thought the universe was made of empty
space & tiny bits of stuff
– He called the tiny bits of stuff “ATOMS”
– He defined atoms were so small, that they
could no longer be divided
– The word atom means “Cannot be divided”
– This is where WE got the word ATOM
What we call an atom!
• Do we completely agree with Democritus?
• WE DIDN’T until the early 1800s
• Scientists built upon his idea to form the
current “Atomic Theory of Matter”
• We currently define an atom as “a small
particle that makes up most types of
matter”
=
Lavoisier’s Idea
• French Chemist (2,000 years AFTER
Democritus)
– Came up with the Theory of Conservation of
Matter
• Which states that matter is neither created or
destroyed –it only changes form
Forest
PLUS
Forest Fire
Equals
ASHES
Answer
Atomic Theory of Matter
• John Dalton, an English school teacher
from the early 1800s, came up with the
idea
• Atoms are incredibly small particles that
have the properties that give the item they
make up their properties
– Gold behaves like gold, because its atoms
behave this way
Gold
So…. How big is an atom??
So…. How big is an atom??
The Basic Unit of Matter is
Atomic Structure
• The center of the
Atom is called the
Nucleus
– It is about 100,000
times smaller than the
entire atom
– It makes up 99.9% of
the mass of the atom
In the Nucleus
• There are two Subatomic Particles
– 1. Proton: Which is a positively charged
particle
– 2. Neutron: Which is a neutrally charged
particle
» These 2 subatomic particles are nearly equal in
mass
Is that it??
• There is one final subatomic particle in an
atom
• This is called an Electron
• Electrons have a negative charge
• They are also not located IN the nucleus
• They travel throughout the atom at high
speeds
• They are EXTREMELY tiny (With the
mass equal to about 1/2000 of a proton
and neutron)
Atomic Model vs. Electron Cloud
• An incredible number of experiments have
been done to try to understand the way an
atom looks and functions
• Currently we have two ways of looking at
the structure of an atom
– The right way…. And the wrong way!
The Wrong (But Easier) Way
• Modern Atomic Model
– Shows electrons orbiting the nucleus of an
atom like planets around the sun
– This is what we commonly think of when we
think of an atom
– It places each electron in its own (or
sometimes a shared) orbit
– Until just recently, we thought this to be
correct
New Model
• As science is forever changing, a new theory
has arose to explain atomic structure
• This is called the Electron Cloud Theory
• This states that electrons move around the
nucleus in an undefined cloud shaped like a
sphere
• This places the electrons in areas similar to an
orbit, where they are more likely to be
# of Electrons vs. Protons
• In a normal atom there will be THE SAME
number of Protons (+) and Electrons (-)
– This makes a Neutral Atom
• However, sometimes an atom is charged!
• If it has a negative charge, it will have
more electrons(-) than protons(+).
• If it is positively charged, it will have more
protons(+) than electrons (-).
Examples
• So if an atom has 3 extra protons, it would
have a charge of what??
• +3
• If an atom had a charge of -2, what does it
look like?
• It has 2 extra electrons
• If an atom has 2 extra protons and 3 extra
electrons it will have a charge of what??
• -1
Properties of H2O
• Hydrogen bonds: Because water is a polar
molecule it can form up to 4 hydrogen bonds
• This allows water to have certain properties:
– Cohesion is the attractive force between
molecules of the same substance
• This allows water to stick to itself
– This is why water beads on a window
– This is why some organisms can stand on top of water
– Adhesion is the attraction between molecules
of different substances
• This allows for water to stick to other things
– This is why water moves up the xylem of a plant
Van Der Waals Forces
• When molecules are close together, a
slight attraction can occur between the
positively and negatively charged regions
of nearby molecules
– This doe not require the molecules to have a
specific or complete charge
• THIS HAPPENS WITH WATER
Atomic Number
• The number of protons not only tells you what
the positive charge is, it also tells you of the
atoms atomic number.
• Its atomic number tells you what Element the
atom is
• An Element consists of entirely ONE type of
atom
• There are only 109 different elements
• 90 of which are found in nature
• 19 were created in a lab
Periodic Table of Elements
•
•
•
•
Why do we need one?
What is the point of classifying things?
Does it speed things up?
Do you think it was easy to make?
Changing Your Numbers
• Changing the number of Protons changes
your element
• Changing your number of electrons
changes your charge to negative or
positive
• What happens if you change the number
of Neutrons????
Isotope
• When you change the number of
Neutrons in an atom you get what is
called an
Isotopes & a Mass Number
• Every element on the periodic table has a
specific Mass Number
• This number indicates the mass of the atom
• The mass comes primarily from the protons &
neutrons in an atom
• Therefore, having a different number of neutrons
(Isotope) will change the mass number
• Isotopes are represented by adding the mass
number to the atom symbol
Numbering & Isotopes
Other Things to Know About Atoms
•
•
•
•
•
Chemical formulas
Radioactive isotopes
Ionic Bonds
Covalent Bonds
Chemical vs. Physical properties
Solids
• Have a definite shape and volume
• Are Solids moving?
• The atoms in a solid vibrate, but keep the
same shape and volume
• Atoms are packed closely together
Liquids
• Has definite volume, but no definite shape
• Has Viscosity
– The strength of attraction between the
particles of a liquid
– Causes a liquid to move slowly
• Like molasses or honey
• Will also have a surface tension
– This often results from hydrogen bonding or
very high viscosity
Gas
• Have No definite shape or volume
• Particles are much further apart
• They will often spread out evenly, trying to
be as far apart form each particle as
possible
• Gas or air pressure results from forcing
the particles closer and closer together
Energy
• Why can’t we increase a liquids energy
endlessly?
• When you boil water, does the
temperature remain constant?
• If the stove top reaches a temperature of
250 degrees Celsius, is the water also 250
degrees Celsius
• Why does water bubble when it boils?
Energy
• Energy is the ability to do work or cause
change
• The energy of motion is called KINETIC
ENERGY
• Particles with more kinetic energy move
Faster & are further apart
• The total energy of all the particles in a
sample of matter is called Thermal
Energy
Temperature
• The average kinetic energy of the
individual particles is called the
Temperature
• The amount of heat required to raise the
temperature of a substance 1 degree
Celsius is called its Specific Heat
• Substances with a low specific heat, such
as metals, heat up quickly
• Does water have a low or high Specific
Heat?
Back to the Oranges
• Again, think of oranges…
• But this time, think of them on the tree
Question!?
• When the fall nights approach freezing in
Florida, farmers come out and spray the
orange trees with water……
• ……………….WHY??
Answer!!
• Water has a higher specific heat than
orange juice
• Therefore an orange can freeze at
temperatures above 0 degrees Celsius
• The water would then act like a blanket for
the orange, keeping the temperature up.
• Also, when the water begins to freeze, it
can protect the juice inside the orange for
a limited amount of time, in the same way
ice protects a lake
Vaporization
• When liquid turns into gas
• Also called evaporation
• The temperature during vaporization does
not change
• Not only temperature, but pressure also
affects this
• The evaporating molecules MUST be at
the surface too
Condensation
• The opposite of vaporization
• A gas turning to liquid
• Heat is lost from the vapor and it changes
form into a liquid
• Think of water on a cold glass on a hot
summer day….Where did it come from?