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

Wastewater Treatment

Sludge Density Index (SDI)

The weight in grams of one mL of sludge after settling for 30 minutes. SDI = 100/SVI.

Process Design Examples

• Complete Mix Activated Sludge (CMAS): Air is blown into the tank to keep the waste mixed with the organisms and to add oxygen to the water. This process removes soluble suspended solids (SS) and ammonia by exposing the waste to organisms.
• Sequencing Batch Reactor (SBR): This reactor operates under non-steady state conditions in a batch mode with aeration and sludge settlement occurring in the same tank. The SBR tank carries out the functions of equalization, aeration, and sedimentation in a time sequence.
• Staged Nitrification Process: Offers greater treatment efficiency and capacity than a single

Metals, Bonding, and Extraction: Key Concepts

Attractive forces in a metallic structure arise because positive ions and electrons attract each other.

High Melting Points

Why does X have a high melting point? Due to its giant covalent structure, a lot of energy is needed to break the strong covalent bonds.

Lattice Structure of Metals

Why do metals have a lattice structure? The atoms in a pure metal are arranged in closely packed layers, which makes them strong.

Alloys

Alloy: A mixture of a metal with at least one other element.

Isotopes

Isotope: An atom with a different number of neutrons.

• The more reactive the metal, the more likely it is to corrode from oxygen and water.

Ores

Ore: A rock that contains enough metal to make mining and extraction economical.... Continue reading "Metals, Bonding, and Extraction: Key Concepts Explained" »

Carbon's Versatility

Carbon is a versatile atom due to its ability to form four covalent bonds with other atoms, including other carbon atoms. This allows carbon to create a wide variety of organic molecules with diverse structures and functions.

Definitions:

• Organic Compound: A compound containing carbon that is typically found in living organisms.
• Hydrocarbon: An organic compound consisting of only carbon and hydrogen atoms.
• Macromolecule: A large molecule formed by the joining of smaller repeating units (monomers). Examples include proteins, carbohydrates, and nucleic acids.

Dehydration and Hydrolysis Reactions

Dehydration Reaction:

A dehydration reaction is a chemical reaction where water is removed from the reactants to form a larger molecule.... Continue reading "Organic Molecules: Structure and Function" »

Solid State Material Classification

Three types of solids are classified according to their atomic arrangement:

• Crystalline Materials: Atoms are arranged in a highly ordered, repeating pattern.
• Amorphous Materials: Atoms lack a long-range ordered structure.
• Polycrystalline Materials: Composed of many small, randomly oriented single-crystalline regions.

Microscopic views illustrate crystalline and amorphous materials, while polycrystalline structures are shown through a more macroscopic view of adjacent single-crystalline regions.

Diamond Structure Discovery and Bragg Diffraction

The discovery of the diamond structure is closely linked to Bragg diffraction. This phenomenon occurs when two beams with identical wavelength and phase approach a crystalline... Continue reading "Solid State Materials: Structure, Properties, and Fabrication" »

Electronegativity

Measure of the tendency of an atom to attract bonding pair of electrons.

Cation

Ion that has a positive charge.

Ionic Bond

Chemical bond formed between two ions with opposite charge.

Anion

Ion that has a negative charge.

Chemical Bond

Electrical attraction between nuclei and valence electrons that binds atoms together.

Covalent Bond

Bond formed when atoms share one or more pairs of electrons.

Non Polar Bond

Type of chemical bond where two atoms share a pair of electrons with each other.

Polar

Uneven distribution of charge.

Polar Bond

Type of chemical bond where a pair of electrons is unequally shared between two atoms.

Molecule

Neutral group of atoms that are held together by covalent bonds.

Molecular Compound

Chemical compound whose simplest... Continue reading "Chemical Bonding and Organic Chemistry" »

Properties of Metals:

Shiny, lustrous, can be polished, strong, and solid.

Nonmetals:

Dull, not lustrous, cannot be polished, weak, half are gases.

18 Families or Groups, 18 Periods:

Elements in the same group have common characteristics. Horizontal is period, vertical is family or group.

Periodic Law:

The PT is organized by atomic number Z. Elements with similar properties are in the same family.

Properties of Metalloids:

Have characteristics of metals and nonmetals. Located between metals and nonmetals.

Johann Dobereiner (1829):

Classified elements into groups of three, called triads.

John Newlands (1838-1898):

Law of Octaves (1863) suggested arranging elements in octaves.

Dmitri Mendeleev (1834-1907):

Published a table of elements organized by increasing... Continue reading "Evolution of the Periodic Table: From Triads to Actinides" »

Thermal Energy and Particle Motion

Thermal energy is intrinsically linked to temperature, which reflects the movement of particles within matter. This concept is a cornerstone of the Kinetic Theory of Matter, stating that all matter is composed of tiny particles in constant, random motion.

Changes in Matter: Physical vs. Chemical

When we observe the world around us, we identify two distinct types of transformations that matter undergoes:

Physical Changes

A physical change is a process where the fundamental nature or chemical composition of a substance remains unaltered. The original substance does not transform into a new, chemically different substance. Examples include:

• Changes of State: Such as ice melting into water, or water boiling into steam.

Mixtures and Compounds

A mixture is a material system made up of two or more different substances which are mixed but not combined chemically.

Types of Mixtures

• Heterogeneous: The components are visibly diverse.
• Homogeneous: The components are uniformly distributed, appearing as a single substance.

Basic Chemical Concepts

• Phase: A physically distinct form of matter, such as a solid, liquid, or gas.
• Element: A substance that is made up of only one type of atom.

Changes of State

• Melting Point: The temperature at which a solid melts. The particles gain energy, vibrate faster, and eventually move around, becoming a liquid.
• Boiling Point: The temperature at which a liquid boils. The particles gain energy, move faster, break free, and become a gas.

Tests for

Understanding Temperature

What is Temperature?

Temperature is the measurement of a substance's thermal energy.

Measuring Temperature

Mercury Thermometer

A mercury thermometer consists of a bulb containing liquid mercury and a thin tube. The liquid expands due to thermal expansion and rises up the tube, allowing the temperature to be read on a calibrated scale.

Digital Thermometer

A digital thermometer uses a microprocessor that measures the temperature and displays it on a liquid crystal display (LCD).

Temperature Scales

Common temperature scales include Celsius (ºC) and Kelvin (ºK).

• Celsius to Kelvin: K = C + 273.15
• Kelvin to Celsius: C = K - 273.15

Heat Transfer Mechanisms

Conduction

Conduction is the transfer of heat energy primarily from solid to solid... Continue reading "Science Essentials: Temperature, Heat, Reactions, Environment" »