Chapter 1. Basic Concepts about Matter
Scientific Method
The scientific method is the process by which scientists develop a body of knowledge to
understand and make use of matter and energy for practical purposes.
The scientific method has five steps
1. Observation.
2. Formulation of a question (hypothesis)
3. Pattern recognition, summarizing information (scientific laws)
4. Developing theories. (Hypothesis and eventfully theory)
5. Further Experimentation and loosing to first step to keep it improving as we discover
more and more.
Data and measurements (1st and 3rd step) –something you can see and measure.
Hypothesis (2nd step) - a guess to try to explain observed data.
The hypothesis is tested by designing and performing experiments.
Scientific Law (3rd step) - large amount of data summarized in a brief statement
Laws are universal and hold everywhere in the observable universe.
Boyle's Law is P1 V1 = P2 V2
Scientific Theory (4th step) - best explanation for various phenomena as of today
(tentative)
Theories are modified or discarded with new observations.
Theories are valuable for their predictive value.
Models ((2nd step) - use of tangible items or pictures to represent invisible processes
1.1 Chemistry: The Study of Matter.
Universe is made up of matter and energy. In sciences we study both non-living and
living matter found in various places.
Definitions:
Chemistry: Chemistry is a branch of science dealing with studying composition, structure,
properties and non-reversible changes or transformations of matter.
Examples of Ares of Sciences/ Chemistry:
Area
What is being
Chemistry/Science studied
Emphasis
General Chemistry
Individual components of all
matter: elements atoms,
molecule, ions and chemical
reactions.
All forms of matter and the
non-reversible changes they
undergo.
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Inorganic Chemistry
All forms of non living
matter made up of all other
elements except carbon and
the non-reversible changes
they undergo.
Individual components of non
living matter: elements,
atoms, molecule, ions and their
chemical reactions.
Organic Chemistry
All forms of carbon
compounds and their nonreversible changes.
Individual components of
carbon compounds: atoms,
molecule, ions and their
chemical reactions
Biochemistry
All forms of living matter
and the non-reversible
changes their compounds
undergo.
Individual components of
bimolecular compounds:
structure function and their
chemical reactions.
Biology
Living matter, organisms and
their tissues.
Origin, structure, development,
function, and distribution of
animals and plants on the earth.
Physics
Matter and energy in a scale
ranging from sub-atomic
particles to planets and stars.
Origin, structure, and their
transformation in a cosmic
scale.
Matter: Matter is any substance which has mass and occupies space. All physical
objects are composed of matter, in the form of atoms and molecules, which are in turn
composed of protons, neutrons, and electrons.
Energy: Comes in different forms - heat (thermal), light (radiant), mechanical,
electrical, chemical, and nuclear energy. Matter release or absorb energy during their
changes.
Identify the matter and energy:
What is matter or energy description below?
1g of sugar, (matter)
1g of sugar produces 200 Kcal, (energy)
1 mole of O2 gas occupies 22.4 L at STP (matter)
1.2 Physical States of Matter
Depending on the temperature matter exists in four different states or phases:
solid, liquid, gas and plasma.
Phase: Phases have distinct properties and are sometimes called states of matter:
gas, liquid, and solid.
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1) Solid
A definite volume
or size and distinct
shape
2) Liquid
A definite volume,
but it takes the
shape of its
container
States
3) Gas
No definite volume
or shape
4) Plasma
All matter will break
down into nuclei and
electrons as
temperature is
increased
Major physical characteristics that define each state are the kinetic energy, heat or
the temperature of the particles of mater, and the attractive forces between particles
of matter determine the physical characteristics of each state. Many common materials
can be seen in the various states of matter depending on temperature.
Question:
a) Solid has
A. a shape and fixed volume
B. no shape, but fixed volume
C. no shape and no fixed volume
D. shape, volume, and takes up space
b) Currently, scientists have proved the existence of how many states of
matter? 4 states.
1.3 Properties of Matter
Matter posses certain characteristic which we call their properties.
Extensive properties depend on the amount of matter.
Intensive properties do not depend on the amount of matter.
Physical properties involve only a change in physical state (a liquid to a solid) and
no change in the identity of substances (water and ice is same substance) making
the matter. Most physical changes are reversible.
Chemical properties involve a change in the identity of substance making the matter.
Chemical changes are non reversible.
Describe each of the following properties and either intensive(I) or extensive(E), and
physical (P) or chemical(C).
1) Mass E P
2) Density I P
5) Color
I P
9) Malleability I P
13) Flammability I, C
3) Temperature I P
4) Length E P
6) Reactivity I, C
7) Heat capacity E P
8) Volume E P
10) Luster I P
11) Specific heat I P
12) Weight E P
16) Viscosity I P
17) Corrosiveness I,
C
14) Melting Point I P
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An example of an extensive property is
a. color. b. freezing point. c. length. d. density.
a
b
c
d
e
1.4 Changes in Matter
Physical change: like physical property involves no change in substance making up
the matter.
Chemical change: like chemical property involves a substance making up the matter.
All materials move from solid to liquid then to gas as the temperature increases. True or
false? True.
What is the term used to describe the phase change as a liquid becomes a solid? Ans:
Freezing.
Is freezing a physical change or chemical change or physical change? No change in
substance therefore physical.
What is the term used to describe the phase change as a sold directly becomes a gas?
Ans: Sublimation
Describe following description as physical (P) or chemical (C) changes.
a. Water boils at 100 degrees Celsius. P
b. Diamonds are capable of cutting glass. P
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c. Water can be separated by electrolysis into hydrogen and oxygen. C
d. Sugar is capable of dissolving in water. P
e. Vinegar will react with baking soda. C
f.
Yeast acts on sugar to form carbon dioxide and ethanol. C
g. Aluminum has a low density. P
h. Ammonia is a gas at room temperature. P
i.
Bromine has a red color. P
j.
Dry ice, solid carbon dioxide, is sublimed at room temperature. P
k. Salt is dissolved in water. P
l.
Iron rusts in a damp environment. C
m. Hydrogen peroxide decomposes to water and oxygen. C
1.5 Pure Substances and Mixtures
Matter is further classified depending the nature and number of substances
making them up. They can be classified in to two broad categories:
a) Pure substances are composed on only one substance with constant
physical (MP and BP) and chemical properties (reactivity).
b) Mixtures are composed of more than one substance in varying proportions
and do not have constant physical (MP and BP) or chemical property.
1.6 Elements and Compounds
Pure substances: with constant physical (MP and BP) and chemical properties could
be classified further into two types:
a) Elements: Most simple form of pure substance that are made up of all the
same type of atom. Example. Oxygen-O2.
They cannot be broken down into two or more elements.
b) Compounds: Substances made from two or more different kinds
of atoms. Example. Water Oxygen-H2O.
They can be broken down into two or more elements.
Mixtures could be further classified onto two types based on the uniformity of
phase/composition thorough out the sample:
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a) Homogeneous Mixtures: Mixtures which are the same throughout with
identical properties everywhere in the mixture. They not easy to separate. This
type of mixture is called a solution.
An example would be sugar dissolved in water or some type of metal alloy
like the chromium-molybdenum steel used in many bike frames.
b) Heterogeneous Mixtures: Mixtures which have different properties when
sampled from different areas. An example would be be sand mixed with water or
peanuts mixed with raisins.
Classes of Matter
1.7 Discovery and Abundance of the Elements.
Over a period of time starting with ancient alchemist, miners, and early
chemists like Antoine Lavoisier many elements were discovered. Currently there
are about 118 known elements listed in the periodic table. Only about 83 of them are
stable and rest of the heavier unstable elements after lead (Pb) decay radioactively
into stable lighter elements. The elements show different abundances cosmically,
and terrestrially in the atmosphere, earth crust, oceans and living organisms.
Cosmic abundance: H, He mainly
Earth crust abundance : O, Si, Al, Fe, etc.
Abundance in living organisms on earth: H, O, C, N
Atmospheric Abundance: N, O
Oceanic Abundance: H, O Na, Cl, Mg, K, Ca, S
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Cosmic
Elements
Cosmic
Mole%
Earth
Elements
Earth
Mole%
Human
Elements
Human
Mole%
H
75
O
47
H
63
He
6
Si
28
O
25.5
O
<1
Al
7.9
C
9.5
C
<1 Fe
4.5
N
1.4
N
<1 Ca
3.5
Ca
0.31
Ne
<1 Na
2.5
P
0.22
Si
<1 K
2.5
S
0.08
Mg
<1 Mg
2.2
Na
0.07
1.8
Names and Chemical Symbols of the Elements.
As new elements are discovered they are given a name. Later they are
assigned a chemical symbols which can be one or two letters. The first letter is
always a capital case and the second letter is always a small case. If symbols does
not correspond to an English name they are taken from the Latin or German names
of elements.
Na = sodium, K = potassium, Fe = iron, Cu = copper, Ag = silver, Sn = tin, Sb =
antimony, W = tungsten, Au = gold, Hg = mercury, Pb = lead
What element has the atomic symbol I?
a) Iodine b) Fluorine c) Copper d) Helium
Match element symbol to the name
Al
1. Iridium
F
Be
2. Beryllium
Ir
4. Fluorine
3. Aluminum
1.9 Atoms and Molecules.
Atom - The smallest unit of an element made up of nucleus and electrons that has
all of the properties of an element.
Molecule -The smallest unit of a pure substance that has the properties of that
substance. It may contain more that one atom and more than one element.
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Homonuclear: made up of same kind of atoms (same elements).
Heteronuclear: made up of different kind of atoms (different elements).
a single
atom
(of an
element)
A homonuclear
diatomic
molecule
(of an element)
a heteronuclear diatomic
molecule
(of a compound)
Note: Atoms don't have a color. The colors here are used to
differentiate between kinds of atoms.
Ions - Charged particles formed by the loss or gain of electrons from atoms or
molecules.
Na (sodium atom )
--Æ Na+ ( sodium ion) + e- (electron) Positive Na+
is also called a cation.
Cl (chlorine atom ) + e- (electron) --Æ Cl- ( chloride ion) Negative ClNa+ is also called anion.
Chemical Models of Matter
Models are commonly used to help visualize atoms and molecules.
For example methane, CH4 could be represented in following ways.
CH4
Chemical Formula
Lewis e-dot structures
Lewis structure
Ball & Stick Models
Space Filling Models
Perspective Drawing
1.10 Chemical Formulas
Each chemical which could be an element or pure substance, has a chemical
formula. Chemical formula gives the type (element symbol) and number atoms
(given as a subscript) of each element that make up a particular chemical
compound.
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A compound is a substance formed when two or more elements which are
chemically joined. Water-H2O, salt-NaCl, and sugar-C12H22O11 are examples of
compounds.
What are the type (the element symbol) and number of atoms in following
chemicals?
Water, salt and sugar
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