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

Classification of Matter: Pure Substances and Mixtures

Pure Substances

Substances that are formed by the same kind of particles (molecules, atoms, etc.).

• Elements: Formed by the same kind of atom. They cannot be divided by chemical means. Examples: Phosphorus (P), Oxygen (O), Carbon (C).
• Compounds: Formed by the same kind of molecules. They can be divided chemically. Examples: Water (H₂O), Carbon Dioxide (CO₂).

Mixtures

Substances that are formed by different kinds of particles.

• Homogeneous (Solutions): The different components cannot be visually distinguished. Example: Seawater.
• Heterogeneous: The different components can be visually distinguished. Example: Granite.

1. Defining the Atom

The atom is the smallest unit of a chemical element that retains... Continue reading "Atomic Theory and Matter Classification: Core Chemistry Concepts" »

Thermodynamics

Specific Heat

Specific heat is the amount of energy required to raise the temperature of 1 kg of a substance by 1 K.

Latent Heat

Latent heat is the amount of thermal energy transferred to 1 kg of a pure substance to change its state at a constant pressure and temperature.

Heat Engine

Heat engines are devices that transform thermal energy into other forms of energy, such as mechanical work.

Atomic Models

Thomson Atomic Model

Proposed by J.J. Thomson, the discoverer of the electron, this theory describes the atom as a sphere of positive charge containing negatively charged electrons.

Rutherford Model

This model consists of two parts:

• Nucleus: Composed of protons and neutrons, containing nearly all the mass and the total positive electric charge

Equi. Homogeneous reactants and products in the same physical state. Equi different heterogeneous. Kc: The law of mass action tells us the equilibrium constant q is the product of the high concentration of the products to their stoichiometric coefficients, divided by the product of the concentrations of the reactants raised to their respective stoichiometric coefficients. The value of Kc is specific for each reaction qiomica and independent of initial concentrations of reactants and products. It just depends on the temperature. T = KC = Degree of dissociation: indicates the amount to as x q open one of reagent reacted. Is the ratio between the amount, expressed in mol, q reagent has reacted and the amount of initial reagent: a = Qc reaction

Fundamentals of Biochemistry

Energy is essential for all biological processes. All atoms contain energy, and they are joined together by chemical bonds, which are crucial for life. We obtain our energy from food, converting it into chemical energy that can be stored and utilized, as opposed to other forms of energy like light and heat that cannot be retained.

Thermodynamics Principles

• First Law: Energy is neither created nor destroyed; it is only transformed from one form to another.
• Second Law: In every energy transmission, some energy is lost, typically as heat, leading to an increase in entropy.

Atomic Structure

The basic units of matter are atoms, composed of three fundamental subatomic particles: neutrons (neutral charge), protons (positive... Continue reading "Biochemical Foundations: Energy, Atoms, and Chemical Bonds" »

Methods of Electrification

There are three primary electrification methods: by rubbing, by contact, and by induction or influence.

Understanding Coulomb's Law

Coulomb's Law: The attractive or repulsive force exerted between two point electric charges is directly proportional to the product of these charges and inversely proportional to the square of the distance that separates them.

Electric Charge: Protons and Electrons

The Formation of Ions

An ion is an atom that has gained or lost one or more electrons.

Structure of the Nuclear Atom

The central atom has a nucleus in which almost all its mass is concentrated, contributed by the protons and neutrons.

The positive charge of protons is compensated by the negatively charged electrons, which are outside... Continue reading "Atomic Structure and Electrification Principles" »

Atomic Structure Fundamentals

The atom is a structure with a core that is very small relative to the total size of the atom.

• Nucleus: Contains protons and neutrons.
• Electrons: Move at a distance from the nucleus that is very large compared to the size of the core.

Isotopes and Chemical Elements

Isotopes are atoms of the same chemical element that have the same number of protons but a different number of neutrons.

Bohr Model vs. Quantum Mechanical Model

The most important difference between these models is as follows:

• Bohr Model: Assumes electrons are in specific orbits at defined distances from the nucleus.
• Quantum Mechanical Model: Provides that electrons occupy positions with varying probabilities; their exact position cannot be predicted accurately.

The Green Revolution

The Green Revolution refers to the significant increase in agricultural productivity achieved through the use of DDT and other pesticides, fertilizers, irrigation, and mechanization.

Overfishing

Overfishing occurs when tons of fish are caught, and fish populations are unable to reproduce quickly enough to compensate.

Sustainable Forestry in Finland

Finland has developed a science and practice of forest conservation and exploitation.

Excessive CO2 Consumption

Excessive consumption of CO2 has led to imbalances, and the effects of these imbalances are well-known. The extremely rapid increase in atmospheric CO2 concentration is often called the "hockey stick" due to its shape. This increase is primarily caused by the use of fossil... Continue reading "Environmental Impacts and Sustainable Energy Sources" »

Fundamentals of Organic Chemistry

Hydrocarbons

Alkanes

These are saturated hydrocarbons with single carbon-carbon bonds.

• General Formula: CnH2n+2
• Suffix: -ane
• Prefixes by Carbon Count:
  • 1C: meth-
  • 2C: eth-
  • 3C: prop-
  • 4C: but-
  • 5C: pent-
  • 6C: hex-

Alkenes

Unsaturated hydrocarbons containing at least one carbon-carbon double bond (C=C).

• General Formula: CnH2n
• Suffix: -ene
• Prefixes by Carbon Count:
  • 2C: eth-
  • 3C: prop-
  • 4C: but-
  • 5C: pent-
  • 6C: hex-

Alkynes

Unsaturated hydrocarbons containing at least one carbon-carbon triple bond.

• General Formula: CnH2n-2
• Suffix: -yne
• Prefixes by Carbon Count:
  • 2C: eth-
  • 3C: prop-
  • 4C: but-
  • 5C: pent-
  • 6C: hex-

Common Functional Groups

• Carboxylic Acids: Suffix is -anoic acid.
• Aldehydes: Suffix is -anal.
• Ketones: General structure R-CO-R', where R can be a hydrogen

Principal Components of Iron-Carbon Alloys

The main components of iron-carbon alloys include:

• Perlite: Thin films formed with ferrite (light gray) and cementite (dark gray). Carbon content is 0.89%. Ferrite is softer, while cementite is harder.
• Ferrite: Almost pure iron, very soft, ductile, and magnetic. Its structure is cubic.
• Cementite: Located on the right side of the eutectoid point due to its carbon composition (Fe3C). It is the hardest and most fragile constituent of steel.
• Austenite
• Martensite
• Ledeburite: Consisting of cementite and austenite.

Thermal Treatments for Steel

Thermal treatments modify the properties of steel:

• Tempering: Increases hardness, toughness, and yield strength, but also increases fragility. Methods include immersion in water,

Characteristics of Lipids and Fats

Lipids are a very heterogeneous group of chemicals, both from a structural point of view and regarding the functions they perform. They are primarily composed of carbon, hydrogen, and oxygen, though the latter is usually present in very low proportions. Some lipids also contain phosphorus, nitrogen, and sulfur. Lipids are a group of organic biomolecules that satisfy two distinguishing characteristics: they are insoluble in water and other polar solvents, and they are soluble in organic solvents (i.e., non-polar solvents such as gasoline or benzene).

Molecular Structure of Fatty Acids

Fatty acids are molecules composed of long aliphatic hydrocarbon chains. These are linear chains with an even number of carbon... Continue reading "Biological Functions and Chemical Properties of Lipids" »