Year 9 Science
Semester 2
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Yearly Exam
Revision
What is ANSTO?
Structure of the Atom
An atom is made up of these different particles
- Proton
The proton is a small particle that has one positive electric charge
- Electron
The electron is a very tiny particle (only 1/1837 of the mass of a
proton) and has one negatives electric charge. This negative electric
charge exactly balances the positives charge of one proton.
- Neutron
The neutron is a small particle (about the same mass of a proton) with
no electric charge. It is neutral.
Model of Atom
Brief history of the atomic model
400 BC (Democritus) He believed atoms are small particle which
- consist of infinite number and are capable
to join together.
1800s (John Dalton) Elements are made of atoms; atoms of the
same element are the same and different
atoms combine is called compounds.
1897s (J.J.Thomson) Provided the first hint that an atom is made
up of even a smaller particle.
1908s (Rutherfords) Gold foil experiment involved firing a
stream of tiny positively charged particles
at a thin sheet of gold foil
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1913 (Niels Bohr) He placed each electron in a specific energy
levels
Contemporary (Modern) Theory The electrons follow wave mechanic.
Electrons with low energy are closer to the
nucleus and high energy are find further in
an atom.
Shell Model & Electron Configuration
1st = 2, 2nd = 8, 3rd = 8, 4th = 18
Electron Configuration tells us how many electrons are in each shell.
Examples
Ion Cation & Anion & Isotope
Ions atoms that have lost and gained electrons. Atoms become ion because
they need to become stable (to have full outer shells) (FULL VALENCE SHELL).
Features of Period Table
Mendeleev developed the first periodic table of the elements. Elements are
arranged accordingly to atomic number. Periods = horizontal rows of elements.
Group (Family) = vertical column of elements with similar properties. Zig Zag
Line = separates metals from non-metals.
Mass number, Atomic number
- Mass Number
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- Atomic Number
Symbols of the first 20 elements
H= He = Helium Li = Lithium Be = B = Boron
Hydrogen Beryllium
C= N = Nitrogen O = Oxygen F= Ne = Neon
Carbon Fluorine
Na = Mg = Al = Si = P=
Sodium Magnesium Aluminium Silicon Phosphoru
s
S = Sulfur Cl = Chlorine Ar = Argon K= Ca =
Potassium Calcium
Metals & Non-Metals
- Non-Metals often gases or dull, brittle solid with low melting points.
Combine with other non-metals to form diatonic molecules. Carbon
Family (Carbon, Sodium, Germanium etc.) , Nitrogen Family (Nitrogen,
Phosphorus, Arsenic), Oxygen Family, Halogen Family (Group 7) are
families of non-metals.
- Metalloids have characteristics of both metals and non-metals. Great
conductors of electricity. Examples: Boron, Silicon, Germanium,
Arsenic, Antimony, Tellurium, Astatine
Radioactivity
If an element is radioactive, this means that its nucleus is breaking
down. Radioactive elements have unstable nuclei. An unstable nucleus will
break down or decay into a more stable nucleus. As the nucleus break down,
it will emit radiation in the form of particles or rays.
Half life - the time it takes for half the atom to decay.
Nuclear fusion fusing (joining) together of 2 or more atoms. E.g The Sun
Nuclear fission- atoms releasing radioactive particles.
Uses of radiation:
There are 3 types of particles that the nucleus can give out from these
radioactive substances:
- Alpha particles 2 protons and 2 electrons
- Beta high speed electrons formed by the breakdown of the neutrons
- Gamma not particles but high energy radiation
Where Nobody has gone Before
The Big Bang Theory
The Big Bang Theory is a model of how universe began. The theory says the
universe began from a very hot and dense state.
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Big B an g h ap pens
t (tim e) = 0s (second)
H ot, d ark un ove rse expands t
= 10 -35s (to th e p ow er of
-35)
U niverse be gin s to cool
dow n Stars and G alax ies
form
t = 380,000 yea rs
t = 1 b illion ye ars
Expansion slow s dow n,
and th en speeds up. t
= 7 billion years
The Sun and Solar System
form
t = 9 billion years
Evidence that supports the Big Bang theory includes redshift and the cosmic
microwave background radiation. Redshift is the effect in which objects, such as
stars and galaxies, moving away from an observer have their wavelengths
lengthened towards the red end of the visible spectrum. The cosmic microwave
is radiation that left over from the Big Bang. The universe is continues to expand.
Life cycle of Stars
Galaxies
The universe is composed of matter (atoms). Earth Solar System Milky Way Galaxy
Local Galaxy Group Universe
Light Year & Speed of Light
It distance it takes for light to travel in 1 year. = 9.46x10 km. Speed of Light said to be a
speed limit because its the fastest thing we can comprehend.
Important of Hubbles microscope
- Images of distant galaxies
- Help u explain star formation
- Confirm expanding universe
Electromagnetic Spectrum
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The electromagnetic spectrum is made up of all the waves that travel the speed
of light but have different frequencies and wavelengths. Although they vary in
frequency and wavelength, they share the same features of all able to travel
through a vacuum, all travel at the speed of 300,000m/sec and all are transverse
waves. Electromagnetic Spectrum includes Gamma Ray, Infrared
Radiation, Microwave, Ultraviolet, Radio Waves, Visible (Light),
Television Waves and X-Rays. Effect of different mediums: sound travels
faster through solids (particles close
together), the liquids, and
gases.
Everyda
uses of the electromagnetic Spectrum
The properties of Light Absorption, Reflection & Refraction
- Absorption
- Reflection
- Refraction
Law of Reflection
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Types of Waves
There are two types of waves, Transverse waves and Longitudinal Waves.
- Transverse Waves - wave
model
Transverse waves are wave in
which the vibrations of the particles
at right angles to the direction in
which the wave travels. In
Transverse Wave, wavelength is
the distance between two
successive crests or two successive troughs. The amplitude is
the distance between the equilibrium to the crest reaches.
Water and sound is the examples of transverse wave.
Frequency: the number of waves that pass a point in 1 second
( measured in Hz)
Pitch: high pitch = high frequency, shorter wavelength and low pitch =
low frequency, longer wavelength
- Longitudinal Waves
Longitudinal waves are waves in which the vibrations of the particles
travel in the same direction as the wave travels. In Longitudinal waves
perspectives, wavelength is the distance between one
successive compression (has a higher particle density) to
another. The amplitude is the maximum distance the vibrating
particle travels from its undisturbed place. Rarefaction is air
molecules farther apart and has a low particle destiny. Sound
wave are example of Longitudinal Waves.
Wave Equation
Speed = Wavelength (m) x Frequency (Hz)
Mirrors & Lens
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