Download Scientific method

Study guide- 1st Bench mark
Most abundant matter - Plasma: matter @ very
high temp w/ positive and negative charges.
Scientific method – a logical
approach to solve technical/
nontechnical problems is called
scientific method.
Compound

Pure substance
Elements
 Making observation
 Hypothesis- a testable
statement is called hypothesis
 Experiment-A procedure used
to test hypothesis
 Developing theories- a theory
is a well tested explaination
for the broad set of
observations.
 Scientific law- it is a concise
statement that summarize the
results of many observations
and experiments.
Metals
Metalloids
Shine
Nonmetal
partial
No shine
Ductile
Parial
Brittle
Good conductor
Good
Bad cond.
Malleanle &
(Only good conduct.or
At high temperature
Conductance)
Homogeneous
(one phase & solution)
Mixture
(Blend of 2 or more)
Heterogeneous
(Non uniform)
Classification of matte (Mass & Volume)
Solid
liquid
Gas
Plasma
1 Shape
Definite Indefinite
Indefinite
Indefinite
2 Volume
Definite Definite
Indefinite
Indefinite
3 Intermolecular forces
Extensive property- properties which depends
upon the amount of matter are called extensive
properties. Mass, volume, amount of heat
stored etc.
Intensive properties- properties independent of
amount of matter are called intensive
properties. These are used to identify matter
are like finger prints. Density, specific heat,
boiling point, melting point etc are examples of
Intensive properties.
Very strong >>stronge > very weak
4 Compressible
No
No
compressible
Physical properties- properties which can be
measured or observed without changing the
identity of matter are called Physical properties.
Examples are density, specific heat, boiling
point, melting point, color, brittle, malleability,
etc.
Grinding _________,
__________
Physical changes- during physical changes the
composition (ID) of substance do not change.
Grinding, melting, boiling, breaking into two
parts, are examples of physical changes.
Condensation __________, sublimation ( S -
gas) ____
Chemical properties- Properties which are
observed with change in composition of
substance are called chemical properties.
Flamability, combustion, rusting, corrosion,
support combustion, neutralization, reactivity
etc. are examples of chemical properties.
Dalton’ atomic theory and Modern atomic
theory
Chemical changes – changes which can be
observed with change in composition (change in
ID). Color change, gas is produced, grass is
growing green, digestion of food, formation of
solids are examples of chemical changes.
Identify the following as physical or chemical
properties
1 Color____________
point_____________,
Melting
boiling point _______
______________
Flammability
Density ___________
of an acid _____
Neutralization
React with ________
___________
corrosion
evaporation
•
Atoms of the given element are identical
in size, mass and other properties
•
Atoms cannot be subdivided, created or
destroyed.
•
Atoms of different elements combine
in simple whole number ratio.
•
In chemical reactions, atoms combines,
separates or rearranges
•
Modern Theory : Atoms of the same
element can be different called isotopes
•
Atoms are subdivided into electrons,
protons, and neutrons
•
Atoms can be destroyed
Who discovered electron and proposed Plum
pudding model of atom?
JJ Thomson
Supports combustion ___
Density___________
•
Name

Cathode rays were attracted towards
positively charge electric plate indicating
of experiment
is
cathode ray experiment
-----
r
Identify the following as physical or chemical
changes
Rusting _______
two pieces_______,
, Breaking a wood into
Burning of candle _______, Melting of wax
______
Grass is growing green _______,
change of leaves ____
color



negative charge of cathode ray particle
called electrons.
Who discovered nucleus –
Ernest Rutherford





Rutherford made a Gold foil
Experiment
Most of the Alpha particles passed
through gold foil – Indicating atom has
most of empty space
Only few were deflected or bounced
back- indicating positive charge at the
center as Alpha particle has positive
charge were deflected by positive
nucleus.
Name/ Symbol Charge Mass/ Location
Proton p
+1 1 In nucleus
Electrons e
-1
0 outside
Neutrons n
0
1
Inide nucl.
Why an atom is neutral?

# positive charge(p) = # negative charges (e)

A X
Z



A= mass # = ( #p + #n)
Z = atomic number = #p
137 Ba
#p = #e = 56,
56
#n =137 -56 = 81
1 Amu = 1/12 mass of Carbon-12
Two isotopes of chlorine 3517Cl and
37 Cl have % abundance of 70% and
17
30% respectively. What is its average
atomic mass? It is closer to isotopes --3517Cl . Why? B/ of more abundance
= 0.7 x 35 + 0.30 x 37 = 35.5 amu
1 mole C = 6.02 x 1023 atoms C
1 Mole C = 12 g C
1 Mole U = 6.02 x 1023 U atoms


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

X-symbol of Element
1 Mole U = 238 g U

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

1 Mole H2O = 6.02 x 1023 molecules
of H2O
1 molecules = 2H + O
1 mole molar mass = 2 + 16 =18 g
# atoms in 1 molecule H2SO4
= 2H + 1 S + 4O =
molar mass = 2x 1 = 1x32 + 4 x 16 =98 amu

# atoms in 1 Molecule of Al2 (SO4)3
= 2Al + 3S + 12O
Molar mass = 2x27 + 3 x 32 + 12x 16
= 342 amu

Elements in Groups & Number of
electrons in the highest orbit are
called Valence electrons (VE).
Groups Called main block elements
Elemental
Groups 1A 2A 3A 4A 5A 6A 7A
1
# VE 1
8A
2 13 14 15 16 17
2 3
4
18
5 6
(Except He has VE -2)
Nuclear chemistry
•
Nuclear Stability
•
Electrostatic force = the force that
causes like electrical charges to
repel each
nucleus.
other.Neutron
stabilizes
•Strong force = the force between
nucleons (protons and neutrons).
• Neutrons increase the attraction
from the strong force without increasing
electrostatic repulsion between nucleons.

What is an alpha particle?
( He2+ - helium nucleus)

Alpha decay = Loss of Mass # = 4,
decrease in Atomic # by 2
Fission is the splitting of atoms
These are usually very large, so that they
are not as stable
Fission chain has three general steps:
1.
Initiation. Reaction of a single
atom starts the chain (e.g., 235U + neutron)
2.
Propagation. 236U fission releases
neutrons that initiate other fissions
3. propagation of chain reaction.
•
Beta () particle = e-
•
How does nucleus emit an e-?
•
 neutron changes into proton &
emits e- called betta decay.
•
 10n  11p + 0-1e
•
Daughter nuclide = parent nuclide
atomic number plus 1
137
55Cs
 13756Ba + 0-1e-