Notes, summaries, assignments, exams, and problems for Chemistry

Fundamental Chemical Definitions

Molecule

The union of atoms.

Lattice

A continuous structure of millions of atoms.

Chemical Bond

The attractive force that keeps atoms united in a molecule or a crystal.

Elementary Chemical Substance

Atoms of the same element that unite.

Chemical Compound

Atoms of different elements that unite.

The Octet Rule

Atoms of different chemical elements tend to join with other atoms to have eight electrons in their outermost shell, known as an octet, to achieve greater stability.

Types of Chemical Bonds

Ionic Bond

The transfer of valence electrons. The ionic bond is the union of oppositely charged ions through electrostatic forces of attraction. In this case, the elements bond to achieve a noble gas electron configuration.

Ionic Crystal

A... Continue reading "Chemical Bonding and Material Attributes" »

Substances, Mixtures, and Separation Techniques

1. Pure Substances vs. Mixtures

• Distilled Water: Pure substance/compound
• Tap Water: Mixture/homogeneous
• Diamond: Pure substance/element
• Gasoline: Mixture/homogeneous
• Wine: Mixture/homogeneous
• Air: Mixture/homogeneous

2. Dalton's Theory

• Matter is made up of indivisible and indestructible atoms.
• All atoms of the same element are equal in mass and properties.
• Compounds are formed by the combination of different elements.

3. Separation Techniques

• Screening: Separates solid particles of different sizes. Instrument: sieve.
• Filtration: Separates solids from liquids. Instrument: filter.
• Evaporation: Separates solids from liquids when the liquid is not needed. Works best with homogeneous mixtures. The process is faster

Aluminum

Aluminum is used in telescopes. Tempered powder paint is used in metal protection and the preparation of alloys. Aluminum forms alloys with other metals. Duralumin, an aluminum alloy, is used in aeronautics because it is very lightweight and has great resistance.

Aluminothermy

Aluminothermy is a metal extraction procedure that reduces metal oxides using aluminum powder. Metals such as chromium, manganese, and molybdenum are obtained using this method.

Salts of Aluminum

Important industrial salts are called alum (double salts).

Natural Aluminum

Aluminum is not found free in the Earth's crust. It is named after these characteristics:

1. Alumina
2. Hydroxide
3. Silicates

Obtaining Aluminum

Aluminum is extracted using the electrolytic method. Bauxite and cryolite... Continue reading "Aluminum, Copper, Polymers, and Ceramics: Properties and Uses" »

Fuel Properties and Combustion

Oil is formed by the decomposition of organic matter, primarily plankton, in marine environments. It contains the remains of animals and is a mineral found in sedimentary rock formations.

Soluble compounds begin to form, undergoing thermal decomposition into hydrocarbons (HC).

Gaseous Fuels

Gaseous fuels, also called hydrocarbons (HC), are designed for use in combustion. They are divided into natural gas fuels and manufactured gaseous fuels.

Advantages and Properties of Gaseous Fuels

The calorific value varies greatly depending on the type of gas and the presence of non-combustible components. Non-combustible components lower the heat efficiency of combustion.

Calorific value is the heat released during combustion.

Specific

States of Matter

Solid State

Solids are characterized by molecules that are tightly packed with minimal empty spaces. They possess a defined shape and volume and do not flow. Examples include: aluminum, diamond, gold, salt, sugar, flour, and cups.

Liquid State

Liquids consist of molecules with disordered empty spaces, allowing them to flow and adopt the shape of their container. They have a defined volume but no definite shape. Examples include: ethanol, milk, oil, paraffin, water, juice, and cologne.

Gaseous State

Gases have no definite form or volume, adopting the shape and volume of their container. Their molecules are extremely separated and spread rapidly. Examples include: chlorine, nitrogen, Tanax (insecticide), Lucu gas, spray paint, and... Continue reading "Matter, Minerals, and Modern Materials: Core Concepts" »

Review Waxing Techniques

Cusp Placement: Marginal Ridge Occlusion (Upper Jaw)

This section details the placement of cusps in the upper jaw to achieve a marginal ridge top occlusion.

1. First premolar: Distal fossa of the first premolar.
2. Second premolar: Distal fossa of the second premolar.
3. First molar: Mesio-lingual cusp, central fossa of first molar.
4. First molar: Disto-lingual cusp, distal marginal ridge of the first molar and mesial marginal ridge of the second molar.
5. Second molar: Mesio-lingual cusp, central fossa of the second molar.
6. Second molar: Disto-lingual cusp, distal marginal ridge of the second molar.

Cusp Placement: Cusp to Fossa Occlusion (Upper Jaw)

This section describes cusp placement in the upper jaw for a cusp to fossa occlusion.

1. First

Mineralogy

Mineralogy is the science that studies the physical and chemical properties of minerals.

Mineral Classifications

Primary Minerals

Primary minerals are minerals found in their original deposits. An example is pyrite (FeS₂), known for its gold-like color and luster.

Secondary Minerals

Secondary minerals form from chemical reactions involving primary minerals. Anglesite (PbSO₄) is a secondary mineral derived from the primary mineral galena (PbS).

Solid Structures

Crystalline Solids

Crystalline solids have particles arranged in an orderly and regular pattern in three dimensions, following a defined geometric structure.

Amorphous Solids

Amorphous solids have particles arranged randomly, similar to the structure of liquids, resulting in a shapeless... Continue reading "Introduction to Mineralogy and Mineral Properties" »

Electric Nature of Matter

Matter undergoes electric phenomena. It can be uncharged (neutral), positively charged, or negatively charged.

• Like charges repel, and opposite charges attract.
• A body is neutral when it has an equal number of positive and negative charges.
• A positively charged body has more positive charges than negative charges.
• A negatively charged body has more negative charges than positive charges.

Electric charge in various media, and the forces exerted between charges, are described by Coulomb's Law.

Coulomb's Law

The force (F) between two point charges (Q₁ and Q₂) is directly proportional to the product of the charges and inversely proportional to the square of the distance (D) between them.

F = k * (Q₁ * Q₂) / D²

Where:

• Q: Electric

Atomic Models

Dalton's Atomic Model

Dalton proposed that atoms are indivisible, compact spheres with specific weights, explaining chemical reactions. However, this model doesn't explain the electrical nature of matter.

Rutherford's Atomic Model

Rutherford's experiment involved firing positively charged alpha particles at a gold foil. Most particles passed through undeflected, some were diverted, and others bounced back, leading to a new understanding of atomic structure.

Chemical Bonds

Ionic Bonds

When a metal is in the presence of a non-metal, a transfer of electrons occurs, forming ions with opposite charges. These ions are held together by electrostatic attraction. The ionic bond forms between ions of opposite charges. Ionic valence refers to... Continue reading "Atomic Models, Chemical Bonds, and Scientific Method" »

Understanding Carbohydrates

Carbohydrates are biomolecules primarily composed of carbon, hydrogen, and oxygen. Their atoms are linked to alcohol groups (hydroxyl groups, -OH) and hydrogen atoms (-H). All carbohydrates contain a carbonyl group (C=O), which can be either an aldehyde group (-CHO) or a ketone group (-CO). Therefore, they can be defined as polyhydroxyaldehydes or polyhydroxyketones.

Classification of Carbohydrates

Carbohydrates are classified into several groups:

• Monosaccharides: Simple sugars made of single units.
• Oligosaccharides: Contain between 2 and 10 monosaccharide units.
• Polysaccharides: Formed by multiple repeating units of monosaccharides, further divided into:
  • Homopolysaccharides: Formed by the repetition of a single monomer.