Transcript Carbon-12 Stable

Physical Science is the study of matter and energy.
It is broken into two main sciences, physics and chemistry
Chemistry- studies the forms of matter and how it interacts
and changes
Physics- studies energy and how it affects matter
What is matter?
Matter is anything that has mass and takes up space
Matter has mass and volume
Mass-the amount of matter in an object
Volume-the amount of space occupied by an object
How is mass measured?
How is volume measured?
Mass is measured using a balance
Volume is measured using a
meter stick and calculations or a
graduated cylinder
Volume
How do you find the volume of a regular shaped object?
(Length)(Width)(Height) = Volume
How do you find the volume of an irregular shaped object?
Place it in a graduated cylinder and observe the
change in water level.
1mL = 1 cm³
Mass
Mass is also known as the measure of inertia
Inertia- tendency of an object to resist a change in its state of motion
Mass is not the same thing as weight!
Weight- measure of gravitational force exerted on an object
Your weight is different on the Moon than on Earth,
but your mass is the same.
Mass
Weight
-constant, no matter where in the
universe the object is
-Varies, depending on where the
object is in the universe
-measured using a balance and
expressed in grams
-measured using a spring scale and
expressed in newtons (unit of force)
Practice using a balance and a spring scale.
Remember that the units are different!
How do we distinguish one example of matter from another?
Physical Properties of Matter
A Physical Property is something that can be observed or measured without changing
the matter’s identity.
-They help you identify a substance
Examples:
Conductivity- ability to transfer heat or electricity
State- solid, liquid, or gas
Density- mass per unity volume of a substance
Solubility- ability to dissolve in another substance
Ductility- ability to bend (be pulled into wire)
Malleability- ability to be flattened without breaking
Color- wavelengths of light reflected by the substance
Hardness-resistance to bending, stretching, or flattening
Density- describes the ratio of mass to volume.
i.e. dense objects have a lot of mass squeezed into a small volume
Density tells you what will float and what will sink.
-If one object is less dense than another, it will float above it.
e.g. oil and water
-Why do boats float?
Boats float because the overall density of the boat (including the air inside of
it) is less than the density of water.
Density = Mass/Volume
The units for density coincide with the equation (g/cm³ or g/mL)
The density of water is 1 g/mL
Anything with a density greater than one sinks. Anything with a density less
than 1 floats.
M
÷
D
÷
X
V
Why does density determine floating and sinking?
-Force of gravity (weight) increases with
mass
-Buoyancy Force is equal to the volume of
the liquid displaced
Basically, the denser the object the greater the
force of gravity and the weaker the buoyancy force.
If gravity is stronger it sinks. If buoyancy is stronger
it floats.
Physical Changes- change of matter from one form to another that does not
involve a chemical change.
-You manipulate one of its physical properties but do not transform it into
a new substance
Examples include:
-Melting
-Freezing
-Vaporization
-Stretching
-Smashing
-sometimes mixing
Physical changes can be undone by physical means (reshaping, adding heat etc.)
States of Matter
There are three main states of matter, Solids, Liquid, and Gas.
-A fourth, plasma, also exists but under rarer circumstances on Earth
Which state matter is in depends on the energy of the molecules and the degree
of entropy.
Entropy- disorder or lack of organizational structure between molecules
-Entropy usually increases as energy increases
-High entropy means matter cannon take a definite shape, low
entropy allows for a definite shape
What is easier to control, a group of tired, well-behaved kids or a group of
sugar-high, hyper kids?
Solids
•low entropy
•definite shape
•definite volume
•usually low energy/temperature
Crystalline- orderly arrangement of
particles
Amorphous-particles arranged in no
specific pattern
Liquid
•Higher entropy
•Indefinite shape (conforms to container)
•Definite volume
•Higher energy/temperature
Surface Tensions- how strong particles at
the surface of a liquid cling to each other.
Viscosity- how much a liquid’s molecules
cling to each other and their
surroundings.
-resistance to flow
Gas
•High Entropy
•Indefinite shape
•Indefinite volume (fills all available space)
•High energy/temperature
Volume, and resultantly pressure on
surrounding matter, increases as
energy/temperature increases
How does matter move from one state to another?
Matter moves from one state to another by adding energy.
The amount of kinetic energy in a molecule (how much it is vibrating in
place) is its temperature.
So…adding or losing heat causes matter to move from one state to another
How much energy a type of matter needs to change states is a physical property
-liquid water can only exist between 0 and 100° Celsius, above that it
changes to gas, below that it changes to ice
Each state change has a name…
Solid to liquid- melting
Liquid to gas- vaporization/evaporation
Gas to liquid- condensation
Liquid to solid- freezing
Solid to gas- sublimation
What about Plasma?
Plasma is similar to gas in that he has no definite shape or volume, but its
particles are electrically charged or ionized.
It carries so much energy that atoms are missing particles, leaving some with
a positive charge and others with a negative charge
Since it is ionized, it reacts to magnetism and can be directed
Common examples of plasma…
-Lighting
-Stars
-Flames
-fluorescent lamps
-neon displays
-plasma TVs
Because of the overwhelming mass of
stars, plasma makes up most of the matter
in the universe
Chemical Properties tell us which chemical changes will take place under certain
conditions.
Chemical Change-When one or more substances transform into one or more new
substances with different properties
Chemical changes take place everywhere. Brainstorm a few examples…
Chemical Properties and Changes
Chemical Properties- characteristics of matter based on its ability to transform
into a new form of matter, to change from one substance to another.
e.g. flammability and reactivity
They can also be used to classify substances, but they are harder to observe
or measure than physical properties
Flammability is a substance’s ability to burn
Reactivity is a substance’s ability to
combine with other substances to form
new substances
e.g. rusting, acid base reactions
How do we know when a chemical change has taken place?
Often the appearance (texture, color, physical state) can
change. Other signs of change include…
-heat
-odor
-fizzing and foaming
-sound
-light
Unlike physical changes, chemical changes are hard to reverse
-You can undo some reactions by chemical means, but most of the time
it is difficult
Elements, Compounds, and Mixtures
We can describe matter based on its physical and chemical properties, but how
do we organize it?
Pure substances- any form of matter made of uniform particles
Mixture- matter made of multiple types of particles that are not chemically bound
Pure substances are split into two categories…
Elements- pure substance made up of only one type of atom
-cannot be broken down into simpler substances by physical or chemical
means
Compounds- pure substance made up of multiple types of atoms, chemically bound
to form particles called molecules
Elements are all made up of different types of atoms and organized according to
their physical and chemical properties on the periodic table.
The three main groups are metals, nonmetals, and metalloids
Metals- shiny, malleable, conductive (to heat and electricity)
Nonmetals- dull, nonconductive, usually brittle (often are gases or liquids at
room temperature)
Metalloids- share properties of both metals and nonmetals
Number of protons and electrons, atomic mass, electronegativity, and polarity
also affect where an element falls on the periodic table.
Based on an element’s position on the periodic table and the properties of the
elements around it you can usually predict its properties
Compounds
Compounds are made of chemically bound elements, but their properties
can be different than the properties of the elements that make them.
dangerous elements can make harmless compounds and vice versa
A type of molecule is always made up of the same ratio of its component elements
Examples- water is always 2 Hydrogen atoms and 1 oxygen
-table salt is always 1 sodium atom and 1 chlorine atom
Compounds can be broken down during a chemical change.
-Sometimes they need a catalyst, sometimes they need an input of
energy, and sometimes they just degrade over time.
Eat a steak, its proteins are broken down into amino acids (mechanical and
chemical digestion) then your body reassembles the amino acids into other
proteins (translation).
Can you come up with any other examples of compound breaking down or
being formed?
Glucose
Deoxyribonucleic acid
Mixtures
You have a mixture when two or more pure substances are blended together with
no particular ratio between the amounts of each substance.
Unlike compounds, they can be separated using only physical means
-distillation (boiling)
-centrifuging (spinning)
Mixtures are categorized by how well they are mixed…
There are three main types of mixtures, solutions, suspensions, and colloids.
Solutions- mixed so well that they look like a single substance
-they have two parts, the solute or substance being dissolved and
the solvent or the substance in which the solute is dissolved
examples…
Suspensions- particles of the added material are large enough that they
eventually settle to the bottom of the mixture.
examples…
Colloids- particles are evenly distributed throughout, large enough to see, but
not large enough to settle to the bottom
-If you shine a light through them they block some of the light.
examples…
What is an atom?
Atoms: Theory and Structure
Atoms are the smallest unit of an element
Each element is made-up of a different type of atom, distinguished by the
number of the different subatomic particles that compose them.
There are three subatomic particles that make-up an atom
Proton: + charge and large mass (1amu)
Neutron: 0 charge and large mass (1amu)
Electron: - charge and small mass
Protons and neutrons are found in the nucleus of the atom and electrons orbit
around it, in what is called the electron cloud.
John Dalton (late 1700’s)- after observing that elements combine in certain proportions
to create compounds and experimenting to test his theory, he published his atomic
theory.
•All substances are made of atoms. Atoms are small particles that cannot be created,
divided, or destroyed.
•Atoms of the same element are exactly alike, and atoms of different elements are
different
•Atoms join with other atoms to form new substances
He was close, but later research required a few changes.
1897- John Thomson discovered that atoms had negatively charged particles
inside them (electrons).
1909- Ernest Rutherford discovered that atoms had to be mostly dead space with
(-)electrons distantly surrounding a dense (+)nucleus.
1913- Niels Bohr proposed that electrons orbit the nucleus at varying energy
levels.
Modern theory states that the paths of an electron cannot definitively be predicted
-electrons roughly move in patterns called orbitals which coincide with
their energy level, but their exact position cannot be determined.
All atoms of a particular element have the same number of protons in their
nucleus, but the number of neutrons can vary.
Carbon-12
Stable
The different versions of an element are called isotopes
-some isotopes are radioactive, which means they decay over time
Atomic Mass Unit (amu)- approximate mass of one proton or neutron
Mass Number- number of protons and neutrons in an atom
Atomic Mass- weighted average mass of the varying isotopes of an element
Chlorine-35 makes up 76% of all chlorine in nature
Chlorine-37 makes up the other 24%
How do we find the atomic mass?
How can we revise Dalton’s Theory?
•All substances are made of atoms, which in turn are made of smaller particles
called electrons, protons, and neutrons.
•They can be divided or combined (difficultly)- nuclear fusion and fission
•Atoms of the same element will all have the same number of protons and
electrons, but the number of neutrons and as a result the mass may vary (isotopes).
•Atoms do join with other atoms to form new substances (compounds)
Chlorine:
(35) (0.76) = 26.60
(37)(0.24) = 8.88
8.88 + 26.60 = 35.48 amu
Try a few…
Boron-10 = 20%
Boron-11 = 80%
Atomic mass =
Silicon-28 = 92%
Silicon-29 = 5%
Silicon-30 =3%
Atomic mass=
Color Quiz
•
An atom is the base unit of a(n)…
– Black- element
-Orange-compound
•
Can you identify the exact position of an electron?
– Black- yes
•
-Orange- no
The weighted average mass of an element’s isotopes is its…
– Black- mass number -Orange- atomic mass
•
Who first attempted to describe atomic theory?
– Black- John Dalton
•
-Orange- Ernest Rutherford
What takes up the most an atom’s volume?
– Black- nucleus
-Orange-Electron Cloud
Periodic Table of Elements
A table that organizes the elements according to their physical and
chemical properties.
An element’s position on the table, relative to those around it, makes it
possible to predict its properties
-atomic mass, melting temperature, electronegativity, polarity, etc.
The periodic table is laid out in groups (vertical columns) and periods (horizontal rows)
The number of valence electrons increases as you move from left to right, so
elements on the left are the most positively charged and elements on the right
are the most negatively charged.
Groups 1-13 are positive
Group 14 is +/Groups 15-18 are negative
What are valence electrons?
Valence electrons are electrons in the outermost shell (energy level) of an
atom and are the ones involved in reacting with other atoms
-they can either be transferred to or shared with another atom in
forming a compound
A full shell (energy level) has 8 electrons, atoms react with other atoms to try
to fill their outer shell.
-Hydrogen and Helium only need 2 for a full shell
If you have 1 valence electron, is it easier to give away that electron or to get 7 more?
Important Metals sections-
•Alkali metals-highly reactive
•Alkaline Earth metals
•Transition metals
Important nonmetal sections•Noble Gases- nonreactive
•Halogens- highly reactive, bind with
metals to form salt
•Lanthanides
•Actinides- all radioactive (decay
over time)
Other elements•Elements between groups 13-16 can be reactive,
but they usually bond covalently rather than
ionically
Different periodic tables provide you with different information about each element, but
they all at the least give you…
•Atomic number
•Atomic mass
•Element symbol
Some element symbols are based on the element’s
Latin names.
Ferrum = Iron
Aurum = Gold
What are chemical reactions/changes?
How do we know when one has happened?
Why do they happen?
Are atoms ever created or destroyed during chemical reactions?
Signs of Chemical Reactions
Chemical reactions often give us physical evidence to know that a reaction is taking
place.
Such as…
Color change
Precipitate formation (forming a solid)
Gas release (creating a gas)
Heat (energy release)
Compounds are represented using chemical formulas (e.g. H2O) and chemical
reactions are represented using chemical equations.
Chemical equations tell you the chemical formulas of all of the compounds
involved and how many of each compound is involved.
We know…
-the number of each compound
-The kinds of atoms involved
-the number of each kind of atom
The compounds entering the reaction are called reactants
The compounds produced in the reaction are called products
The one BIG rule
The atoms in the reactants much equal the atoms in the products
The Law of Conservation of Mass
-Mass (matter) is neither created nor destroyed during a normal chemical or
physical reaction
As a result the atoms present before a reaction must also be present after a
reaction
To balance equations and make sure that no matter is lost or created, we use
coefficients.
-they tell us how many of a particular compound is involved in a reaction
-By adding them to one, two, or all of the compounds involved in a reaction
we can be sure that the same number of atoms enter and leave a reaction.
CO2
+
H2O
C6H12O6
+
O2
6CO2
+
6H2O
C6H12O6
+
6O2
Balancing chemical equations is part of a branch of chemistry called
Stoichiometry
http://education.jlab.org/elementbalancing/i
ndex.html
Color Quiz
Which is not a sign of a chemical reaction?
Green- breaking into pieces
Orange- changing color
When two liquids mix and a solid forms, the solid is called a …
Green- precipitate
Orange- sublimation
Matter can be created but not destroyed.
Green- True
Orange- False
To balance a chemical equation, we add…
Green- Subscripts
Orange- Coefficients
A balanced equation must have the same number of ________ on each side.
Green- Atoms
Orange- Compounds