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Democritus
460-370 B.C.
Greek philosopher who proposed the concept of the atom.
Democritus's Ideas:
--Matter is composed of empty space through which atoms move
--Atoms are solid, homogeneous, indestructible, and indivisible
--Different kinds of atoms have different sizes and shapes
--The differeing properties of matter are due to the size, shape, and movement of atoms
--Apparent changes in matter result from changes in the groupings of atoms and not from changes in the atoms themselves -
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Aristotle
384-322 B.C.
Greek Philosopher who was very influential in the rejection of the concept of the atom.
--One of the most influential philosophers
--Wrote extensively on many subects, including politics, ethics, nature, physics, and astronomy
--Most of his writings have been lost through the ages -
The Microscope
About 1590, two Dutch spectacle makers, Zaccharias Janssen and his son Hans, while experimenting with several lenses in a tube, discovered that nearby objects appeared greatly enlarged. That was the forerunner of the compound microscope and of the telescope. In 1609, Galileo, father of modern physics and astronomy, heard of these early experiments, worked out the principles of lenses, and made a much better instrument with a focusing device. -
The Submarine
VideoThe first submarine was a rowboat covered with greased leather. It was the idea of Cornelius Van Drebbel, a Dutch doctor living in England, in 1620. Van Drebbel's submarine was powered by rowers pulling on oars that protruded through flexible leather seals in the hull. Snorkel air tubes were held above the surface by floats, thus permitting a submergence time of several hours. Van Drebbel's submarine successfully maneuvered at depths of 12 to 15 feet. -
Steam Engine
Thomas Savery was an English military engineer and inventor who in 1698, patented the first crude steam engine. -
John Dalton
1766-1844
Dalton's Atomic Theory was a breakthrough in our understanding of matter:
-All matter is composed of extremely small particles=atoms
-All atoms of an element=identical, having same size, mass & chemical properties. Atoms of specific element are diff from those of anyother element
-Atoms can't be created, divided into smaller particles or destroyed
-Different atoms combine in simple wholenumber ratios to form compounds
-In a chemical reaction, atoms are separated, combined or rearranged -
The Automobile
The very first self-propelled road vehicle was invented by French mechanic, Nicolas Joseph Cugnot. -
Antonie Lavoisier
Video Hindenburg--French scientist
Lavoisier copiled a list of 23 elements known during the 1790s
In 1783 he named hydrogen for the water that forms when hydrogen and oxygen combine--he used the Greek roots for water (hydro) and to form (genes) -
Cotton Gin
VideoEli Whitney patented the cotton gin on March 14, 1794. The cotton gin is a machine that separates seeds, hulls and other unwanted materials from cotton after it has been picked. -
Joseph Proust
1754-1826
Proust's best known work was derived from a controversy with C.L. Berthollet. Berthollet did not believe that substances always combine in constant & definite proportions as Proust did. Proust eventually was able to prove him wrong in 1799 & published his own hypothesis.
Proust was interested in studying sugars that are present in sweet vegetables and fruits so he demostrated to his class how the sugar in grapes is identical to that found in honey. This later became known as glucose. -
Amadeo Avogadro
--Italian physicist and lawyer
He determined the volume of one mole of a gas.
Avogadro's number: 6,022 136 7 X 10^23 -
The Camera
Joseph Nicéphore Niépce created the first photographic image with a camera obscura, however, the image required eight hours of light exposure and later faded. -
William Crookes
He was an English physicist who noticed a flash of light within a tube while working in a laboratory. It was produced by some form of radiation striking a light-producing coating that had been applied to the end of a tube. He found it was rays traveling from the cathode to the anode within the tube=cathode ray. The accidental invention of the cathode ray led to the invention of the television. -
The Telephone
VideoThe telephone was invented by Alexander Grahm Bell. he telephone is an instrument that converts voice and sound signals into electrical impulses for transmission by wire to a different location, where another telephone receives the electrical impulses and turns them back into recognizable sounds. -
The Light Bulb
Thomas EdisonThomas Edison's greatest challenge was the development of a practical incandescent, electric light. He didn't "invent" the lightbulb, but rather he improved upon a 50-year-old idea. In 1879, using lower current electricity, a small carbonized filament, and an improved vacuum inside the globe, he was able to produce a reliable, long-lasting source of light. -
The Television
Paul Nipkow invented the first television when he sent images over wires using a rotating metal disk technology with 18 lines of resolution. Television then evolved along two paths, mechanical based on Nipkow's rotating disks, and electronic based on the cathode ray tube. -
J.J. Thomson
1856-1940
--He identified the first subatomic particle--the electron
He was an Enlish physicist who began a series of cathode ray tube experiments in the late 1890s to determine the ratio of its charge to its mass. To do this, he carefully measured the effect of both magnetic & electric fields on a cathode ray which determined the charge-to-mass ratio of the charged particle. Then he compared that to other ratios. Thomson concluded that there were particles smaller than the atom. -
Madame(Marie) Curie
1867-1934
Marie & her husband Pierre took Becquerel's mineral sample (called pitchblende) & isolated the components emitting the rays. They concluded that the darkening of the photographic plates was due to ray emitted specifically from the uranium atoms present in the mineral sample. Marie named this process radioactivity. In 1898 the Curies identified 2 new elements-polonium & radium. The Curies shared the 1903 Prize w/Becquerel & also received the 1911 Nobel Prize in Chemistry. -
Max Planck
1858-1947
--German physicist
Planck began searching for an explanation as he studied th light emitted from heated objects, which led him to a conclusion: matter can gain or lose energy only in small, specific amounts called quanta. Quantum: the minimum amount of energy that can be gained or lost by an atom.
Planck's constant: Equantum = hv -
Henri Becquerel
Henri Becquerel1852-1908
--French physicist
Becquerel studied minerals that emit light after being exposed to sunlight--known as phosphorescence. Building on Roentgen's work, he wanted to determine whether phosphorescent minerals also emitted X rays. He accidentally discovered that phos. uranium salts-even when not exposed to light-produced spontaneous emissions that darkened photographic plates. In 1903 he won the Nobel Prize in Physics for his work. -
Albert Einstein
While explaining the photoelectric effect, Einstein proposed in 1905 that electromagnetic radiation has both wavelike & particlelike natures. --While a beam of light has many wavelike characteristics, it also can be thought of as a beam of tiny particles, or bundles of energy, called photons.
Photon: A particle of electromagnetic radiation with no mass that carries a quantum of energy
E,photon = hv -
Robert Milikan
1868-1953
--An American physicist who determined the charge of an electron
Mass of an electron = 9.1 x 10^-28g = 1/1840 mass of a hydrogen atom
--This equation is within 1% of the currently accepted value and he measured it almost one hundred year ago -
Ernest Rutherford
1871-1937
--New-Zealand born physicist and chemist who became known as the father of nuclear physics
Gold Foil Experiment:
--The Rutherford model of the atom in 1911 showed that it had a very small charged nucleus which contianed much of the atom's mass, was orbited by low-mass electrons
--Rutherford became the first prson in 1919 to deliberately transumate one element into another -
Niels Bohr
--A young Danish physicist who worked in Rutherford's laboratory
He proposed a quantum model for the hydrogen atom that answered 'Why are elements atomic emission sprectra discontinuous rather than continuous?' The model also correctly predicted the frequencies of the lines in hydrogens atomic emission spectrum. Then later he went further by relating the hydrogen atoms energy states to the motion of the electron within the atom. --The smaller the electrons orbit, the lower the atoms energy state -
Louis de Broglie
1892-1987
--A young French graduate student in physics
He proposed an idea that eventually accounted for the fixed energy levels of Bohr's model
de Broglie equation: Wavelength = h/Mass(Velocity)
--predicts that all moving particles have wave characteristics -
Erwin Schrodinger
1887-1961
--Austrian physicist
Schrodinger furthered the wave-particle theory proposed by de Broglie. He formulated an equation that treated the hydrogen atom's electron as a wave. This new model for the hydrogen atom applied equally well to atoms of other elements, which Bohr's model did not do.
--Quantum mechanical model of the atom: atomic model in which electrons are treated as waves -
Werner Heisenberg
1901-1976
--German theoretical physicist
Heisenberg concluded that it is impossible to make any measurement on an object without disturbing the object--at least a little.
--Heisenberg uncertainty principle: states that it is fundamentally impossible to know precisely both the velocity and position of a particle at the same time -
James Chadwick
1891-1974
--Enligh physicist, Rutherford's coworker
--He showed that the nucleus also contained another subatomic particle, a neutral particle called the neutron
--Neutron: has a mass nearly equal to a proton, but it carries no electrical charge -
Henry Moseley
1887-1915
--English Scientist
Moseley discovered that atoms of each element contain a unique positive charge in their nuclei
--This means the number of protons in an atom identifies it as an atom of a particular element; referred to as the element's atomic number
Atomic Number = Number of Protons = Number of Electrons -
Penicillin
VideoPenicillin was invented by Alexander Fleming, John Sheehan, Andrew J Moyer. Penicillin is one of the earliest discovered and widely used antibiotic agents, derived from the Penicillium mold.
