Understanding Matter and Energy: Properties, Laws, and Atomic Structure
**Physical Property**
All properties of matter are subject to the scientific method: observation, hypothesis formulation, experimentation, communication of results, and extraction of conclusions.
**Physics**
Studies the changes in materials in which the substances are not transformed into other new substances.
**Chemistry**
Studies the transformations that substances can experience: structure, composition, and properties.
**Absolute Error**
The difference in absolute value between the approximate value obtained in the measurement and the true or accurate value of the measure.
**Relative Error**
The ratio of the absolute error and the true value or accurate measure.
**Electrification**
A phenomenon by which bodies acquire an electric charge.
**Coulomb’s Law**
The intensity of the attraction force or repulsion between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance separating them.
**Electricity**
The displacement of electric charges through a conductor.
**Electric Generator**
Any device capable of transforming some form of energy into electrical energy.
**Electromotive Force**
The power that a generator communicates to each unit of load.
**Electric or Electrostatic Forces**
Attractive or repulsive forces that appear between bodies that have electric charges.
**Power Plant**
An installation in which any form of energy is transformed on a large scale into electrical energy for distribution and consumption.
**Electric Receiver**
Any device capable of transforming electrical energy into other forms of energy.
**Solid**
Rigid, hard to compress, fixed volume, and generally high density. They do not mix with other solids. The forces of attraction are intense, the particles are very close to each other, occupying fixed positions. The particles only have vibrational motion around their equilibrium position.
**Liquid**
Not rigid, not easy to compress, fixed volume, variable shape, generally high density, and they easily mix with other liquids. The forces of attraction are intense, the particles are very close to each other, do not occupy fixed positions, and the particles have some freedom to move around.
**Gaseous**
Variable volume and shape, low density, and they mix easily with other gases. The forces of attraction are negligible, the particles are far apart and in disorder. The particles move freely and collide elastically.
**Kinetic-Molecular Model**
Based on the fact that matter is discontinuous, with particles in motion, maintaining cohesion due to forces of attraction.
**Boyle’s Law**
At a constant temperature, by increasing the volume of a gas, its pressure decreases.
**Law of Charles and Gay-Lussac**
At constant pressure, if we increase the temperature, we must increase the volume.
**States of Matter**
- Vaporization: Liquid to gas
- Condensation: Gas to liquid
- Solidification: Liquid to solid
- Fusion: Solid to liquid
- Sublimation: Solid to gas
- Condensation to solid: Gas to solid
**Heterogeneous Matter**
Matter in which different parts are distinguished, their properties vary, and they can be separated into simpler substances by physical processes.
**Homogeneous Matter**
Different parts are not distinguished, their properties are the same at all points.
- Homogeneous mixture: Homogeneous matter with variable composition.
**Pure Substance**
Homogeneous matter with a fixed composition.
**Compound**
A pure substance that can be decomposed into other simpler substances by chemical methods.
**Element**
A pure substance that cannot be decomposed into other simpler substances.
**Separation of Mixtures**
- Homogeneous: Distillation and crystallization
- Heterogeneous: Filtration and decantation
**Solute**
A substance that dissolves and is the component that is in a lesser amount.
**Solvent**
A substance in which a solute dissolves and is the component found in greater quantity.
**Saturated Solution**
One that, at a given temperature, no longer supports more solute.
**Solubility of a Substance**
In a solvent at a given temperature, it is the maximum amount of solute that can be dissolved in a fixed amount of solvent at that temperature.
**Dalton’s Atomic Theory**
Matter is formed by small, separate, and indivisible particles called atoms. A substance has all its atoms equal. A compound has different atoms.
**Parts of the Atom**
- Nucleus: Contains protons (+) and neutrons (no charge).
- Shell: Contains electrons (-) distributed in different energy levels and atomic orbitals.
**Atomic Number (Z)**
The number of protons in the nucleus of an atom of an element (bottom).
**Mass Number (A)**
The sum of protons and neutrons that an atom has in its nucleus. It is the number of nucleons (top).
**Isotopes**
Atomic forms of the same element that differ in their isotopic mass.
**Isotopic Mass**
The number of times that the mass of an atom’s isotope contains the atomic mass unit (u), which is 1/12 of the mass of a carbon-12 atom.
**Natural Radioactivity**
A spontaneous process of emission of radiation by unstable atomic nuclei that are transformed into other nuclei. They can be alpha, beta, and gamma.
**Artificial Radioactivity**
Present in some stable isotopes when bombarded with different particles.
**Molecules**
Formed by two or more atoms of the same or different elements.
**Crystalline Networks**
Formed by an indeterminate number of elementary particles that are arranged in an orderly structure.
**Chemical Bond**
The union established between the elementary particles that constitute a substance. There are three types:
**Ionic Bond**
The union that results from the presence of electrostatic attraction forces between ions of different signs.
**Covalent Bond**
The union of two or more atoms that share one or more pairs of electrons.
**Metallic Bond**
The union that exists between the atoms of metals that are found forming a crystalline network.
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