Atomic Theory: A Historical Timeline of Discoveries
Evolution of the Atomic Theory
5th Century BC: Leucippus and Democritus
Leucippus and his pupil Democritus proposed the idea that matter consisted of tiny, indivisible particles called atoms. These ideas were opposed by one of the greatest thinkers of that time, Aristotle. It was only after two millennia that the idea of the atom as a fundamental component of matter was taken up again.
1808: John Dalton’s Atomic Theory
John Dalton proposed the Atomic Theory, which revived and gave scientific value to
Read MoreChemical Equilibrium and Thermodynamics: Key Concepts
States of Aggregation of Matter
- In liquids, as in gases, there is no internal order.
- The change from liquid to gas phase involves a reduction of entropy.
- For a gas mixture, Dalton’s Law states: PA = Pº WxH.
- Avogadro’s Law states that V1N2 = V2N1.
Internal Energy and Enthalpy
- The internal energy change along a constant pressure process is equal to the heat of reaction.
- The variation of enthalpy in a constant pressure process is equal to the heat of reaction at constant volume over P)V.
- The heat brought
Firearm Ammunition: Components and Types
Definition of Bullet
A bullet refers to a spherical or cylindrical, pointed shell, usually made of lead or iron. As a projectile, bullets are part of the ammunition, that is, the supplies needed to operate a firearm.
Description of Bullets
A 9mm Parabellum caliber bullet for firearms has an armored, ogival-cylindrical structure. Its body is composed of a shell, powder, and a percussion cap.
Shell
A cylindrical, metallic container or receptacle that serves as a carrier of the propellant charge (powder)
Read MoreElectrolysis: Understanding Key Concepts and Operating Modes
Electrolysis
Electrolysis applies to a reaction which causes a chemical change when an electric current passes through an electrolyte solution. Oxidation (loss of electrons) takes place at the anode, and reduction (gain of electrons) occurs at the cathode.
Electrode Potential
When a conductor (electrode) is placed in contact with an electrolytic solution, a spontaneous electrical potential difference occurs at the electrode-solution interface. This difference is the electrode potential and is measured
Read MoreChemical Reactions and Matter: Understanding the Basics
Chemistry: Reactions and Matter
Chemical Reactions
Chemical reactions are the processes by which one or more substances are transformed into one or more different substances.
Pure Substances
A pure substance is a type of material that cannot be separated into other types of matter by the simplest physical methods and has a constant composition.
- Element: A pure substance that cannot be decomposed by chemical processes.
- Compound: A pure substance formed by two or more chemically bonded elements in fixed
Atomic Models and Chemical Compounds: A Comprehensive Study
Atomic Models and Chemical Compounds
Thomson’s Atomic Model
Imagine the atom as a lump of positively charged matter with negatively charged electrons embedded within it, like a watermelon.
Rutherford’s Gold Foil Experiment
Rutherford decided to bombard atoms in a very thin gold foil with projectiles. He used newly discovered particles, much smaller than atoms but very heavy, with a mass four times greater than that of a hydrogen atom and a charge twice that of an electron, but positive. These particles
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