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" »

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

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

Ideal Diodes

What is the main difference between a simple key and an ideal diode?

A: The ideal diode can drive in a single direction.

Semiconductor Materials

Semiconductor, Resistivity, Resistance, and Ohmic Contact

A: A semiconductor is a material with a conductivity level between a conductor and an insulator.

Resistivity is a measure of how readily a material allows the passage of an electric charge. Lower resistivity indicates a material that easily conducts electricity. It's used to compare the resistance levels of different materials.

Atomic Structure of Copper and Conductivity

What makes copper a good conductor is that its valence electrons (copper has one electron in its outermost layer) are weakly bound to the atom and can be easily moved.

Intrinsic,

The Chemical Industry's Role in Food Production

Food doesn't come directly from nature; it requires the chemical industry for production, preservation, and preparation. Production involves fertilizers, pesticides, and fuel for machinery. Conditioning includes packaging, refrigeration materials, preservatives, and sterilization processes for microorganism control. Preparation uses fuel, containers, and spices for flavor and easier digestion. Most materials in our homes are not in their natural state but come from the chemical industry.

Improved Nutrition and Health

Life expectancy in Europe has doubled in the last 200 years due to improved nutrition, hygiene, and medicine. Water chlorination uses chlorine to prevent diseases like cholera, typhoid,... Continue reading "Chemical Industry's Impact on Food, Health, and Environment" »

Essential Chemistry Concepts

1. Thermochemistry

Thermochemistry is the branch of chemistry that studies the changes in temperature that occur during a chemical reaction.

2. Heat of Formation

Heat of formation is the energy inherent in elements, which is transformed when it receives energy from an external source.

3. Heat of Reaction

Heat of reaction is the energy absorbed or released during a chemical reaction.

4. First Law of Thermodynamics

The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transformed.

5. What is a Solution?

A solution is a mixture of two or more components with a uniform consistency.

6. Types of Solutions

• Homogeneous
• Heterogeneous
• Simple Solution
• Colloid
• Suspension

7.

Subatomic Particles: Components of the Atom

Atoms are composed of tiny particles called subatomic particles:

• Electron

  Discovered by J.J. Thomson in 1897 while studying cathode rays produced in an evacuated glass tube with a voltage of about 10,000 volts. The electron is a negatively charged particle (on the order of $10^{-19}$ coulombs) with a mass of approximately $10^{-31}$ kg.

• Proton

  Discovered by Ernest Rutherford in 1919. It is a positively charged particle with a magnitude equal to the electron's charge and a mass approximately 1,840 times greater than the electron's mass.

• Neutron

  Discovered by James Chadwick in 1932. He worked with radiation emitted by beryllium when bombarded with alpha particles (originating from radioactive emissions). The