Notes, summaries, assignments, exams, and exercises for Chemistry for Secondary education

Plastic Materials: Organic Polymers & Classification

Plastic materials are organic polymers. According to their physical properties or their use, polymers can be classified into:

• Plastics: Polymerization Reactions & Types

  Plastics are produced by polymerization reactions. Some common plastics produced by addition polymerization include polyethylene, polypropylene, polyvinyl acetate, polystyrene, and acrylics.

  • Polyethylene: Used in the manufacture of bags, plastic containers, bottles, and toys.
  • Polystyrene: Used for the elaboration of foam for packaging, thermal insulation, and toys.
  • Condensation Polymerization: A process that forms the polymer and water as another product.

• Resins: Versatile Polymers & Applications

  These are polymers such

Electrochemistry and Electrolysis

Electrochemistry studies the transformation between electrical energy and chemical energy. Electrolysis is the decomposition of a substance by means of an electric current.

Classification of Conductors

A conductor is a substance that allows the passage of electric current. They are classified as follows:

• Conductors of the first kind: Metals are characterized by conducting electrical current without changing their structure.
• Second-class conductors: Compounds, either fused or in solution, conduct electric current; however, as the current passes, chemical bonds are broken and the substances are converted into other materials.
• Covalent compounds: These compounds have covalent bonds and do not conduct current.

Industrial

Pure Substances and Matter Classification

A homogeneous material made up of one kind of substance is a pure substance.

Every pure substance differs from others by its characteristic properties, which allow recognition.

Chemical Compounds and Elements

A chemical compound is a pure substance that can decompose, sometimes with difficulty, into simpler substances.

An element is a pure substance that cannot be broken down into more simple substances. Elements combine to create new pure substances, which are compounds.

The two most abundant elements in Earth's crust are oxygen and silicon.

Properties of Metals and Non-metals

• Metals are generally good conductors of heat and electricity.
• Non-metals (except for graphite) are poor conductors of heat and electricity.

Understanding Atoms and Subatomic Particles

All matter consists of particles called atoms. An atom is composed of smaller elements known as subatomic particles:

• Protons: Possess a positive electric charge and are located in the nucleus.
• Neutrons: Carry no electric charge and are located in the nucleus alongside protons.
• Electrons: Carry a negative electrical charge and orbit in the electron cloud.

Dalton's Atomic Theory

In 1808, John Dalton retrieved the atomic theory of Democritus. He proposed that atoms were indivisible particles and the ultimate constituents of matter that combined to form compounds.

The Plum Pudding Model

Experiments conducted in 1897 on the conduction of electricity through gases led to the discovery of the negatively charged...

The Octet Rule

In chemical compounds, atoms tend to exchange electrons with other atoms to complete 8 electrons in their valence shell, with the exception of hydrogen, which requires 2 electrons.

Ionic Bonds

Ionic bonds result from the electrical attraction between positive and negative ions. Metals typically form ionic compounds when reacting with nonmetals.

Properties of Ionic Bonds

• Solid at room temperature with very high melting and boiling points.
• Hard and resistant to scratching.
• Do not conduct electricity in a solid state.
• Soluble in water and conduct electricity when fused.

Covalent Bonds

Covalent bonds occur when two atoms share pairs of electrons to complete their valence shells.

Properties of Covalent Bonds

• Solid at room temperature.
• High melting

Propiedades y Ensayos de los Metales

Elementos metálicos puros

No se pueden emplear para la fabricación de piezas. Las aleaciones (dos o más elementos) mejoran sus propiedades.

Propiedades de los metales

• Dureza: Oposición al rayado o penetración. Da idea de la resistencia de un material a la deformación permanente.
• Elasticidad: Capacidad de recuperación al cesar la fuerza que los deforma. El límite elástico es la fuerza máxima de deformación.
• Tenacidad: Propiedad que tienen los metales de no romperse. Se opone a la rotura y absorbe la fuerza; da idea de la capacidad que tiene un metal de absorber energía antes de romperse.
• Fragilidad: Facilidad de rotura bajo la acción del choque.
• Fatiga: Resistencia que tiene un material de no romperse

Chemical Bonding and Structure

Forming Molecules

In composites, clustering involves forming molecules. Atoms of different non-metal elements are joined to form molecules.

Ionic Crystals

When metals bind to nonmetals, they form ions of two types. Metals typically form positive ions, and nonmetals form negative ions, which are held together by electrostatic attraction.

For example, a sodium atom gives one electron to a chlorine atom, becoming Na⁺ and Cl^- ions. These ions attract each other. When this happens, many atoms can form a crystal lattice where the ions alternate in a three-dimensional network.

Atomic and Molecular Mass

The atomic mass of an atom is the average mass of its isotopes. It is typically found in the periodic table, often below the...

Atomic Structure and Properties

• Atom: The core structure of matter, containing a nucleus of protons and neutrons with electrons moving around it.
• Isotopes: Atoms of the same chemical element that possess the same number of protons but a different number of neutrons.
• Bohr Model: A model where electrons are restricted to specific energy levels.
• Orbital: A region of space with a high probability (above 90%) of finding an electron.
• Electronic Configuration: The distribution of electrons around the nucleus of an atom.
• Valence Electrons: Electrons located in the outermost shell, responsible for the chemical behavior of the atom.
• Valency: The number of electrons an atom needs to gain or lose to complete its outermost shell.
• Metals: Elements that tend to lose

Foundations of Atomic Theory

Early Concepts of Matter

Democritus (5th Century BC): Proposed that atoms are indivisible particles.

Renaissance (16th Century): This era marked the beginning of scientific observation based on experimentation and measurement.

Boyle and Dalton: Robert Boyle defined the chemical element. John Dalton was the first to gather experimental data to develop a comprehensive theory on the subject.

Avogadro: Pioneered the study of gases, leading to significant insights into molecular behavior.

States of Matter

General Properties of Matter

Matter possesses mass and occupies volume, presenting in three key states:

Liquid State

• Possesses fixed mass and volume.
• Adapts its shape to the container.
• The forces maintaining the particles allow

Chemical Bonding and Atomic Properties

1) In the compound NaCl:
I. A pair of atoms share their electronic link (F)
II. Sodium presents the electronic configuration of Neon (V)
III. Chlorine presents the electronic configuration of Argon (V)

2) In the compound MgCl₂, we can say that magnesium:
I. Has an octet in its valence shell (V)
II. Lost 2 electrons (V)
III. Gained 2 electrons (F)
IV. Shares its valence electrons (F)

4) Given the compounds PCl₅, BF₃, CH₄, and XeF₄, it is possible to say:
I. Carbon (C) satisfies the octet rule (V)
II. The compound BF₃ has 26 total valence electrons (F)
III. P and Xe have 5 and 8 valence electrons, respectively (V)

Stoichiometry and Chemical Reactions

6) One of the main reactions in the metallurgy of Iron (Fe)