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Physical Science Reviewer for third quarter

Science

  • - From the Latin scientia, meaning “knowledge” may be defined as an organized body of knowledge about the natural universe and the processes by which that knowledge is acquired and tested.

Physical Science

  • 1. Chemistry study of the composition and structure of matter and the chemical reactions by which substances are changed into other substances.

    2. Physics:

  • Matter is anything that has mass and takes up space. (Solid, Liquid, Mass)

  • Atom is the fundamental unit of all matter; basic unit of a chemical element.

Parts of an atom:

  • - Neutron no charge part of the nucleus.

  • - Proton positively charged part of the nucleus.

  • - Electron negatively charged surround the nucleus.

Atomic number refers to the number of protons in their atom. The number of protons determines what element an atom is.

Isotopes are members of a family of an element that all have the same number of protons but different numbers of neutrons.

Atomic mass equal to the sum of the individual particle masses of an atom. It is typically calculated by adding the number of protons and neutrons together.

Atomic weight weighted average of the atomic mass of all natural isotopes of an elements

Ions are atoms with unequal number of protons and electrons which results in an overall positive or negative charge.

Bigbang the exponential expansion of a singularity more than 13 billion years ago.

Big Bang: Summary of Events

● Initial Singularity the universe began as an extremely hot and dense point called a singularity. All matter, energy, space, and time were compressed into this tiny, infinitely small point.

● Cosmic Expansion (BigBang) Around 13.8 billion years ago, this singularity underwent a rapid and exponential expansion, creating space and time as we know it.

● Formation of Elementary Particles In the first few moments after the Big Bang, the universe was incredibly hot. As it expanded and cooled, elementary particles such as quarks and electrons formed.

● Formation of Atoms After about 380,000 years, the universe had cooled enough for protons and neutrons to combine and form simple atoms, mainly hydrogen and helium.

Nucleosynthesis The process of making new atomic nuclei from pre-existing nuclei, protons and neutrons.

Formation of Elements:

  • - Big Bang Nucleosynthesis

  • - Stellar Nucleosynthesis

  • - Supernova Nucleosynthesis

  • - Synthesis

  • - of other elements

1. Big Bang Nucleosynthesis:

  • - Nucleosynthesis process that formed the first three elements in the periodic table —Hydrogen, Helium, and Lithium.

2. Stellar Nucleosynthesis:

  • - The word “stellar” means star and the formation of elements in the center of the star is called stellar nucleosynthesis.

  • Star is a luminous, hot, and massive ball of gas, mostly hydrogen and helium, held together by its own enormous gravity.

  • Fe heaviest element that can be fused in the star.

  • Star life Cycle

Nebula:

  • - A cloud of gas and dust in outer space

  • - Gas in nebula is used to make new stars and dying stars create nebulae from their gas.

  • - Fist stars were formed from clouds made of almost only Hydrogen and Helium.

Protostar:

  • - Over time, the hydrogen gas in the nebula is pulled together by gravity and it begins to spin. As the gas spins faster, it heats up and becomes a protostar.

Average Star Main Sequence Star:

  • - Eventually the temperature reaches 15,000,000 degrees and nuclear fushion occursin the cloud’s core.

  • - The star gives off light and heat produced by nuclear fushion.

  • - The onset of nuclear fusion signal the transition of a protostar.

  • - Fusion in the core continues as long as there is hydrogen to fuel it.

  • - The main sequence star will remain in this stage, shining for millions to billions of years to come. This is the stage our Sun at right now.

Nuclear Fusion:

  • - A nuclear reaction on which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy.

  • The energy released by Fusion counteracts gravity crushing inward.

  • A more massive stars has more fuel which determines the fate of the star.

The proton-proton chain reaction (average star):

  • - In this process the average star gets its energy and convert Hydrogen into Helium.

  • - It startswith a proton and a neutron which fuse together to form Deuterium.

  • - When another proton collides with Deuterium, Helium-3 is formed. This process is known as Deuterium Burning.

  • - Collision between the Helium-3 atom with another Helium-3 forms Helium-4.

Average Star:

  • - When the hydrogen supply in the core begins to run out, and the star is no longer generating heat by nuclear fusion, the core becomes unstable and contracts. The outer shell of the star, which is still mostly hydrogen, starts to expands. As it expands, it cools and glows red – and becomes Red Giant.

  • - This star will be a Red Giant for around a billion years but after all the hydrogen is gone, the core gets smaller and hotter and enters helium flash.

  • - The core remains as a White Dwarf and eventually cools to become a black dwarf.

  • Triple-alpha process (Average Star)

  • - The combination or fusion of three alpha particles (hrlium nuclei 4He) to form a carbon nucleus (12C).

Massive Star:

  • - More mass means more inward force, so the star is much hotter.

  • - Hotter temperature means faster fusion.

  • - If the remnant of the explosion is 1.4 to about 3 times as massive as our Sun, it will collapse into a very small, very dense core of neutrons called a neutron star.

  • - If the remnant is more than three times as massive as the Sun, gravity overwhelms the neutrons and the star collapses completely into a Black Hole.

  • - The matter within is so compressed and the pull of gravity is so intense that even light is drawn in and not reflected.

  • - Red Supergiant

  • - A star accumulates more mass and continues to grow into red super giant.

  • - Alpha particle fusion happens at its core and creates more heavy elements until Iron. This is known as the Alpha ladder process.

  • - Supernova

  • - The biggest explosion that humans have ever seen. Each blast is the extremely bright, super-powerful explosion of a star.

  • - All the heavy elements are synthesized during this event.

  • - Neutron capture is the addition of neutron to a seed nucleus. There are two

    Principle paths to building the elements heavier than Fe: (1) S-process (Slow

    Addition of neutrons) and (2) R-process (Rapid addition of neutrons).

S-Process:

  • - Slow process happens when there is a slow rate of capturing neutron while there is a faster rate of radioactive decay hence increasing the proton by 1.

  • - Can produce elements up to #83-Bismuth.

R-Process:

  • - Rapid process means that there is faster rate of capturing neutron before it undergoes radioactive decay thus, more neutron can be combined in the nucleus. This is what happens in a supernova forming heavier elements that iron with the process known as supernova nucleosynthesis.

  • - Can produce Uranium.

Types of Radioactive Decay:

  • Alpha Decay (-2 protons, -2 neutrons)

  • Beta Decay (+1 proton, -1 neutron, -1 electron)

  • Gamma Decay (-1 photon)

Types of Beta Decay:

● Beta minus decay involves the transformation of a neutron into a proton, leading to an increase in the atomic number of the atom. The neutron is neutral, while the proton has a positive charge.

● Beta plus decay, a proton disintegrates to yield a neutron, causing a decrease in the atomic number of the radioactive sample. The nucleus experiences a loss of a proton but gains a neutron.

Radionuclide an unstable form of a chemical element that releases radiation as it breaks down and becomes more stable.

DMITRI MENDELEEV:

  • - He is best known as the “Father of the Periodic Table”, which he invented in 1869.

  • - He created a classification of elements based on their atomic weight.

HENRY MOSELEY:

  • - He was an English physicist and his experiment demonstrated that the major properties of an element are determined by the atomic number, not by the atomic weight, and firmly established the relationship between atomic number and the charge of the atomic nucleus.

  • - He proposed that the elements atomic number was uniquely tied to their “positive charge.” This discovery allowed for a better arrangement of the periodic table, and predicted elements that were not yet discovered.

  • - When the elements were arranged according to their atomic numbers, there were four gaps in the table. These gaps corresponded to the atomic number 43, 61, 85, and 87. These elements were later synthesized in the laboratory through nuclear transmutations.

Discovery of Nuclear Transmutation:

Ernest Rutherford:

  • - In 1919, he successfully carried out a nuclear transmutation reaction - a reaction involving the transformation of one element or isotope into another element. The first nuclide to be prepared by artificial mean was an isotope of oxygen, (17,O,8)

  • - It was made by Ernest Rutherford in 1919 by bombarding nitrogen atoms with a particles.

  • - however , both alpha particles and atomic nuclei are positively charged, so they repel each other. Therefore, instead of using fast moving alpha particles in synthesizing new elements, atomic nuclei are often bombarded with neutrons (neutral particles) in particle accelerators.

JAMES CHADWICK:

  • - The British physicist, james chadwick, discovered neutrons in the year 1932. He was awarded the nobel prize in physics in the year 1935 for this discovery.

  • Discovery of the Missing Elements

  • - Recall that in 1925, there were four vacancies in the periodic table corresponding to the atomic numbers 43, 61, 85 and 87.

Technetium:

  • - The first synthesized element that does not occur naturally on earth, technetium, was created by bombardment of molydenum by deuterons, by Emilio Segre and Carlo Perrier in 1937.

  • Francium

  • - Is a heavy chemical element. It was discovered in 1939 in France by French physicist, Marguerite Catherine Perey.

Astatine:

  • - In 1940, Dale Corson, K. Mackenzie, and Emilio Segre discovered element with atomic number 85. They bombarded atoms of bismuth with fast-moving alpha particles in a cyclotron.

  • Cyclotron is a particle accelerator that uses alternating electric field to accelerate particles that move in a spiral path in the presence of a magnetic field. It is invented by Ernest O. Lawrence in 1929-1930.

Promethium:

  • - Element-61 (Promethium) was discovered as a decay product of the fission of uranium. It was discovered in 1945 by Jacob A. Marinsky, Lawrence E. Glendenin and Charles D. Coryell.

Synthetic Elements:

  • Is one of 24 chemical elements (atomic number 95-118) that do not occur naturally on Earth: they have been created by human manipulation of fundamental particles in a nuclear reactor, a particle accelerator, or the explosion of an atomic bomb; thus, they are called “synthetic”, “artificial”, or “man-made”.

Transuranic Elements:

  • - Also known as transuranium elements are the elements with a higher atomic number than uranium (greater than 92).

Uranium:

  • - The heaviest naturally occurring elements.

  • Early in 1940, Edwin McMillan proved that an element having an atomic number 93 could be created. He used a particle accelerator to bombard uranium with neutrons and created an element with an atomic number 93 which he named neptunium.

Neptunium:

  • - The first transuranium element.

  • - At the end of 1940, element-94 was synthesized by Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl. They bombarded uranium with deuterons (particles composed of a proton and a neutron) in a cyclotron. Element-94 was named Plutonium.

Polarity of Molecules:

  • - NonPolar

  • - Polar

Intramolecular Forces:

  • - Are forces that hold atoms in a molecule. These forces are responsible for the formation of chemical bonds. Chemical bonds are formed when atoms lose, accept or share electrons.

Difference between Molecule & Compound

Molecule:

  • - The smallest units of a compound that retains the characters of the compound.

  • - Smallest particle of substance that retains the chemical. A group of like or different atoms held together by chemical forces

Compound:

  • - Contains atoms of different elements chemically combined together ina fixed ratio.

  • - Represented using a formula

  • - The list of compound is endless.

Ionic Bond:

  • - Occurs when there is a transfer of one or more valence electrons from one atom to another. It exists between metal & non-metal atoms where metal loses electrons while non-metal accepts the electrons donated by the metal.

Covalent Bond:

  • - When two non-metal atoms combine, neither of them loses or gains electron. Instead, electron pairs are being shared by both atoms and the type of chemical bond formed is called covalent bond.

Polarity of Molecules is determined by the two factors:

Polarity of bonds based on:

  • - Electronegativity

  • - Molecular Geometry

Electronegativity:

  • - Measures the relative tendency of an atom to attract electrons to itself when chemically combined with another atom.

  • - The higher the value of EN, the element tends to attract electron towards itself.

Example formula:

1. Ca and Cl

(Solutions)

Step1:

Ca = 1.0

Cl = 3.0

Step 2:

1.0 - 3.0 = |-2.0| = 2.0

Step 3:

Anwer 2.0

Type of bond Ionic Bond:

Polarity of Bonds:

  • Nonpolar covalent bonding electrons are shared equally

  • Polar covalent bonding electrons are shared unequally

  • Ionic bonding electrons are transferred

    Molecular Geometry:

  • - Both the bond polarity and molecular shape determine the overall molecular polarity. In terms of molecular geometry, the valence shell electron pair repulsion (VSEPR) theory would help us to determine the spatial arrangement of atoms in a polyatomic molecule.

Solubility defined as the ability of a substance (solid, liquid, gas) to dissolve in a given substance (solid, liquid, or gas).

Miscibility is the property of two substances to mix in all proportions, forming a homogeneous mixture. The term is most often applied to liquids.

“Water and oil do not mix. They are said to be immiscible. Coz water is polar while oil is nonpolar.”

Intermolecular Forces hold multiple molecules together and determine many of a substance’s properties.

Intermolecular Forces: State of Matter:

  • - The state of a substance at room temperature depends on the strength of its IMFs.

  • - The strength og IMFA greatly affects the physical properties of substances such as boiling point, melting point, vapor pressure, surface tension.

  • - Strong intermolecular forces tend to yield solids and liquids while weak intermolecular forces favor formation of gases.

● Boiling point is the temperature at which the vapor pressure and atmospheric pressure of a liquid substance are equal.

● Melting Point is the temperature at which solid becomes liquid. At this point, the solid and liquid phases exist in equilibrium.

● Surface tension is the attractive force found in liquids which is responsible for pulling surface molecules in the rest of the liquid. Further, it minimizes the surface area.

● Viscosity is a measure of a liquid’s resistance to flow. The greater the viscosity of a liquid, the more slowly it flows.

● Volatility measures the rate at which a substance vaporizes (changes from liquid to gas)

VAN DER WAALS FORCES:

  • - Van der Waals forces, after the Dutch chemist Johannes van der Waals (1837-1923) consist of dipole-dipole interaction, dipole-induced dipole interaction and dispersion forces.

Dipole-Dipole Interaction:

  • - Present among polar molecules.

  • - The positive (+) end of one molecule is attracted to the negative (-) end of the other molecule.

Dipole-Induced Dipole Interaction:

  • - Present among polar and nonpolar molecules.

London Dispersion Forces:

  • - Occur between temporary or induced dipoles

  • - These are the weakest of all the intermolecular forces.

  • - Increase as the molecular mass of a substance increases.

Ion:

  • - Defined as an atom or molecule

Ion-Dipole Interaction:

  • - Results from the attraction either between a cation (+) or an anion (-) with permanent polar molecules. The ions will be attracted to the opposite charges present in the dipole resulting to this type of attractio.

H-Bonding:

  • - A special type of dipole-dipole interaction between the H-atoms in a polar bond.

“Vapor pressure and Volatility decrease with increasing strength of intermolecular forces”