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

The Four Primary Types of Semantic Change

1. Generalization (Broadening)

A word that originally had a specific meaning becomes more general.

• Pigeon: At first meaning just the young dove, it became more general, referring to all pigeons (or sometimes specifically male pigeons).
• Guy: An eponym derived from Guy Fawkes. It was first used for someone grotesque, but now generally means 'man' or 'fellow'.

2. Specification (Narrowing)

The opposite process of generalization, where a word's meaning becomes more specific.

• Meat: Old English (OE) mete referred to food in general. Now it specifically refers to animal flesh.
• Engine: Originally any mechanical device (from Latin ingenium, meaning innate quality or clever invention). Now it refers specifically to a

Dalton's Atomic Theory and Chemical Composition

Dalton's theory states that elements consist of atoms, which are material particles that are separate and indestructible. Atoms of the same element are equal in mass and in all other qualities. The atoms of different elements have different mass properties. Compounds are formed by the joining of atoms of the corresponding elements in a simple numerical relationship. The "atoms" of a given compound are, in turn, identical in mass and all other properties.

Pure Substances and Elements

• A pure substance is a homogeneous system that has a defined and constant composition, possessing invariant physical properties, and cannot be separated by physical processes.
• A chemical element is a pure substance that

Agitation and Mixing: Core Definitions

Agitation is the operation of creating violent, irregular motions within a fluid material. Its primary purpose is to ensure particles or molecules of one or more phases are distributed efficiently, achieving desired results in the shortest time and with minimum energy.

If two or more substances, whether miscible or not, receive this movement, the process is called mixing. Mixing aims to achieve a random distribution of these substances or phases.

Overall Aims of Agitation

Overall, agitation aims to:

• Produce and maintain an even distribution of materials undergoing treatment, or increase the speed at which this occurs.
• Produce and maintain an even heat distribution.
• Increase the active specific surface area of

Physical Properties of Matter

A physical property is a feature that can be studied using the senses or by measuring with a specific instrument. These properties manifest themselves primarily in physical processes such as state changes, temperature changes, pressure changes, etc.

• Examples include color, hardness, density, boiling point, and melting point.

Physical properties are categorized as:

• General Properties: A single value can be applied to different substances, such as mass, volume, color, and texture.
• Specific Properties: Each substance has a particular value, such as density, specific gravity, boiling point, and melting point.

Chemical Properties of Matter

Chemical properties are distinctive characteristics of substances observed when they... Continue reading "Understanding the Physical and Chemical Properties of Matter" »

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.

Material Preparation and Addition Techniques

The preparation should be correct to ensure maximum production of high-grade mixed materials. Some materials contain much fine dust and air; you must compact or wet them before they are added to the mix. A light solvent can be used to moisten the dust and expel air, or you can increase the density by mechanical means if you cannot moisten it. It is sometimes necessary to remove the absorbed gas via vacuum. These types of substances have to be added as they dry. Before entering the mixer, they should be fluffed, either by passing them through a mesh or by shredding. The mixing time decreases and the product is more uniform if lumps are released. If the solids present in small amounts are soluble in... Continue reading "Industrial Solid Mixing and Material Preparation Techniques" »

Copper Alloys: Properties and Applications

Copper is a metal with significant industrial applications, both in its pure form and as a component in alloys. These include:

• Bronze

  These are alloys of copper and tin, often with other elements. They offer excellent corrosion resistance and are much harder and stronger than either copper or tin. Notable types include regular bronze, phosphor bronze, leaded bronze, and silicon bronze.

• Brass

  These are alloys of copper and zinc, characterized by their pale yellow color and capacity for great brilliance and polish.

• Cuproaluminum

  These are alloys of copper and aluminum. They offer greater resistance to corrosion than pure copper due to the presence of aluminum. They are particularly resistant to seawater and

Element: refers to a class of atoms, all s them with the same number of protons in its nucleus. Although traditionally chemical element can be defined as that substance that can not be decomposed by chemical reaction, into simpler COMPOUND: a substance formed by the joining of two or more elements of the periodic table, in a fixed ratio . MIXTURE: A mixture is a material system consisting of two or more pure substances, without chemical reaction chemically. AGGREGATION STATES OF MATTER: In chemistry shows that, for any substance or material element, changing the conditions of temperature or pressure, can be obtained from different states or phases, known as states of aggregation of matter in relation to the binding forces of the particles (... Continue reading "Coh3 chemical name" »

Electrical Conductivity in Water

Electrical Conductivity: Pure water is a poor conductor of electricity. It is the impurities in the water, such as dissolved salts, which allow water to conduct electricity. It is found that a great indicator of the total level of impurities in fresh water is its electrical conductivity—the efficiency with which water transmits electrical current.

The more impurities it contains, the higher the electrical conductivity. For domestic purposes, the preferred water has a total dissolved solids (TDS) content of less than 500 ppm, or a conductivity below approximately 750 microSiemens (ohm⁻¹).

Water Alkalinity and pH Resistance

Alkalinity: Alkalinity is the measure of water's resistance to reductions in pH when acids... Continue reading "Key Indicators of Water Quality and Mineral Content" »

Essential Bioelements in Living Organisms

Bioelements are chemical elements that constitute biomolecules. The majority have incomplete external electronic layers and a lower atomic number, allowing them to be easily incorporated into living organisms.

Classification of Bioelements

• Primary Bioelements: These majority elements constitute 99% of living matter and include C, H, O, N, P, and S.
• Secondary Bioelements: Found in all living things, but to a lesser extent, these include Na, K, Ca, Mg, and Cl.
• Trace Elements: Present in proportions below 0.1%, these are equally essential. Some, such as Fe, Cu, Zn, Mn, I, Ni, and Co, are present in most organisms. Others, like Si, F, Cr, Li, B, Mo, and Al, are found only in specific groups.

Biomolecules: The