Transcript Test Prep Middle Grades

1. Characteristics of States of Matter
Solid
Liquid
Gas
- Retains a fixed
volume and
shape
- Assumes the
shape of the
part of the
container which
it occupies
- Assumes the
shape and
volume of its
container
- Not easily
compressible
- Does not flow
easily
- Not easily
compressible
- Flows easily
- Compressible
- Flows easily
2. Pressure-Temperature Relationship in Gases
Combined Gas Law:
According to the law, if volume remains constant,
pressure will change in proportion to temperature.
101kPa • 0.100m3
273k
=
303kPa • 0.100m3
819k
KiloPascal (kPa) - metric unit for pressure
Kelvin (k) - Standard International
unit of temperature
3. Atomic Structure
•1803 John Dalton proposed an "atomic theory"
with spherical solid atoms based upon measurable
properties of mass. “Solid Sphere Model”
•1898 JJ Thomson used a CRT to experimentally
determine the charge to mass ratio of an electron.
“Plum Pudding Model” / Electrons
•1911 Rutherford Nucleus is dense, small, and
positively charged. Electrons are located outside
the nucleus. “Planetary Model” / Nucleus
•1922 Niels Bohr Developed an explanation of
atomic structure that underlies regularities of
the periodic table of elements. “Electron Shells”
4. Element, Compound, Mixture, & Alloy
Element - A substance composed of atoms having an identical
number of protons in each nucleus. Elements cannot be
reduced to simpler substances by normal chemical means.
Compound - A chemical bond consisting of atoms or ions of
two or more different elements in definite proportions that
cannot be separated by physical means.
Mixture - A composition of two or more substances that are
not chemically combined with each other and are capable of
being separated.
Alloy - A homogeneous mixture or solid solution of two or
more metals, the atoms of one replacing or occupying
interstitial positions between the atoms of the other.
5. Balancing Chemical Equations
Valence shells must balance out electrons:
Iron - is +3 valent
Oxygen - is -2 valent
Therefore…
4Fe + 3O2 --> 2Fe2O3
4(+3)
3(-4)
+12
-12
2(+6) 2(-6)
+12
-12
6. Chemical Bonding (Page 1 of 2)
Ionic Bond: electrons are transferred forming
positive & negative ions that attract
yields
Electron transfer of
sodium to chlorine
Covalent Bond:
Ionic bond forming
sodium chloride
atoms share electrons
Two types of covalent bonds:
Nonpolar Bonds
Polar Bonds
(electrons equally shared)
H2
(electrons unequally shared)
H2O
6. Chemical Bonding (Page 2 of 2)
Fact:
When comparing a polar and
nonpolar molecule with similar
molar mass, the polar one
generally has a higher boiling
point.
7. Reaction Types
A combination (synthesis) reaction is where two or more
substances are bonded together to produce a single product.
A reaction of the type: A + B --> AB
Decomposition is the fragmentation of a chemical compound
into elements or smaller compounds.
A reaction of the type: AB --> A + B
A double-displacement reaction is where parts of two reacting
structures swap places.
A reaction of the type: AB + CD --> AD + CB
A single-displacement reaction is where one element appears
to move out of one compound and into another.
A reaction of the type: A + BX --> AX + B
8. Hooke’s Law
Hooke's Law of elasticity is an approximation that states that
the amount by which a material body is deformed (the strain)
is related to the force causing the deformation (the stress).
For systems that obey Hooke's law, the extension produced is
directly proportional to the load:
F = -kx
- x is the distance the spring is elongated by
- F is the restoring force exerted by the spring
- k is the spring constant or force constant of the spring
9. Newton’s Laws
First Law - An object will stay at rest or move at a constant
velocity (constant speed in a straight line) unless acted upon
by an unbalanced force.
Second Law - The rate of change of the momentum of a body
is directly proportional to the net force acting on it, and the
direction of the change in momentum takes place in the
direction of the net force.
Third Law - For every action (force applied) there is an
equal but opposite reaction (equal force applied in the
opposite direction).
10. Waveforms (Page 1 of 2)
Crest
III
I
IV
Trough
II
I - Amplitude
II, III - Wavelength or Period
IV - Peak to Peak
10. Waveforms (Page 2 of 2)
Types of waves:
Frequency is the
measurement of the
number of times
a repeated event
occurs per unit of
time.
The frequency of
these waves = 3Hz
1s
To calculate the frequency of an event, the number of
occurrences of the event within a fixed time interval are
counted, and then divided by the length of the time interval.
11. Wave Effects (Page 1 of 2)
The Doppler Effect is the apparent change in frequency and
wavelength of a wave that is perceived by an observer moving
relative to the source of the waves.
This source of waves is moving to the
left. The frequency is higher on the left,
and lower on the right.
Destructive Interference:
Two waves out of phase with
troughs & peaks / subtract amplitudes
A = IA1-A2I
Constructive Interference:
Two waves in phase with troughs
& peaks line up / add amplitudes
A = A1+A2
11. Wave Effects (Page 2 of 2)
Diffraction is the bending of waves around obstacles and the
spreading out of waves beyond openings.
12. Static Electricity
Like charges repel.
Unlike charges attract.
13. Current Electricity (Page 1 of 2)
Series Circuits
Current remains constant but voltage
drops differently across components
of the circuit that have resistance.
Parallel Circuits
Voltages across components are the
same, but each component drops
different amounts of current.
13. Current Electricity (Page 2 of 2)
In order for the second bulb to be inserted in
series with the first, it must be placed in a
position where it will drop voltage that is
running throughout the entire circuit, not just
across one of the parallel resistors.
14. Converting Energy
Generator
chemical energy --> mechanical energy --> electrical energy
Transformer
steps-up or steps-down electrical energy
Motor
electrical energy --> mechanical energy
Rectifier
changes AC (alternating current) to DC (direct current)
15. Circular Velocity / Acceleration
The velocity vector “v” is always perpendicular to
the position vector “R”. The circular motion of
the velocity is shown in the circle on the right,
along with its constant acceleration.
16. Phase Changes
lose energy
Melting
gain energy
Solids melting into liquids must gain energy.
Evaporation
Liquids evaporating into gases must gain energy.
Condensation
Gases condensing into liquids or liquids condensing into
solids must lose (release) energy.
Sublimation
Solids subliming into gases must gain energy.
17. Thermal Energy
Thermal Energy
The average kinetic energy of
molecules in a system