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

Since antiquity, attempts were made to understand matter by dividing it into its tiny parts. The Greeks called these tiny, allegedly invisible parts of matter 'atoms'.

Dalton's Atomic Theory

In 1808, John Dalton took the ideas of the Greeks and further developed them into a comprehensive theory. Key definitions and postulates from his theory include:

• Matter consists of indivisible particles called atoms.
• An element is a substance composed of identical atoms.
• A compound is a substance formed by atoms of two or more different elements combined in fixed ratios.

It is important to note that Dalton believed atoms were indivisible, a concept later disproven by the discovery of subatomic particles.

The Electrical Nature of Matter

Experiments can easily demonstrate... Continue reading "Unraveling the Atom: From Ancient Ideas to Modern Structure" »

Noncyclic Photophosphorylation

This process is similar to what occurs after the electron transport chain in the mitochondrial membrane.

• With the stroma, protons are transported to the lumen through the fixed plastoquinone.
• This generates a potential gradient that moves to an enzyme, ATPase, located in F particles, similar to those of mitochondria.
• ATPase uses four protons to phosphorylate ADP to ATP.

Cyclic Photophosphorylation

This occurs when:

• Light striking the plant is between 681 and 700 nm, exciting only Photosystem I (PSI).
• The plant urgently needs ATP, as this process is faster than noncyclic photophosphorylation and does not waste energy reducing NADP when not needed.

The process unfolds as follows:

1. PSI donates electrons to the acceptor chain,

Electron Transport Chain

Steps in the Electron Transport Chain

1. Electrons and protons carried by NADH + H⁺ are transferred to FMN, reducing it.
2. FMN is oxidized, transferring its electrons to Coenzyme Q (CoQ), which is reduced. This allows FMN to accept more electrons and continue the chain.
3. CoQ is oxidized and passes its electrons to the next acceptor, a cytochrome. Cytochromes are dehydrogenases.
4. Cytochromes transport protons into the mitochondrial matrix. The chain continues with the electrons.
5. Cytochromes are iron-sulfur molecules. The iron is oxidized (ferric) or reduced (ferrous) Fe. Each iron atom carries one electron, so the process occurs twice.
6. Cytochromes following CoQ in the chain are Cyt b, Cyt c, and Cyt a3.
7. Electrons reach the end of

Characteristics of Matter

Matter has mass; that is, when placed on a scale, it creates an imbalance. Matter is impenetrable, as two bodies cannot occupy the same space simultaneously. Matter occupies a space, meaning it has volume. The common component is called matter. Bodies are a limited portion of matter, distinguished by features such as color, texture, smell, etc. Each particular kind of matter is a substance, such as sulfur, cotton, or sugar.

Intensive Properties

Intensive properties do not depend on the amount or form of the substance. Examples include:

• Chemical composition
• Vapor pressure
• Density
• Effusion point
• Fragrance
• Taste

Extensive Properties

Extensive properties directly depend on the amount of substance. Examples include:

• Mass
• Volume
• Smell
• Surface
• Height
• Weight

States

Understanding Atomic Structure

Atomic Number

The atomic number (Z) is the number of protons in an atom. In a neutral atom, the number of electrons is equal to the number of protons.

Mass Number

The mass number (A) of an atom is the total number of protons (Z) and neutrons (n) in the nucleus. Therefore, A = Z + n.

Atomic Mass

The atomic mass is the mass of a single atom. Because the masses of atoms are very small, they are typically expressed using atomic mass units (amu) rather than SI units.

Isotopes

Isotopes are atoms of the same element that have the same atomic number but different mass numbers. Isotopes of an element have the same number of protons but different numbers of neutrons.

Atomic Orbitals (Electron Shells)

Atomic orbitals, or electron... Continue reading "Understanding Atomic Structure: Number, Mass, Isotopes, and Ions" »

Cytology Fixatives

Solution: Cytology fixatives, formerly employing ether/alcohol 96 in equal parts, are now rarely used due to the hazardous nature of ether. The 96% alcohol is most often used. The procedure involves immersing the preparation in the fixative bath for a minimum of 10 to 15 minutes. Other alcohols, such as 100% methanol, 80% propanol, and 80% isopropanol, can also be used. Citospray is used in samples obtained by forced exfoliation.

Sample Types in a Cytology Laboratory

Samples that can reach the lab from samples obtained by:

• Forced exfoliation: Rubbing or scraping with various instruments. This is applied to the skin and organs accessible from the outside.
• Spontaneous exfoliation: Samples containing spontaneously exfoliating

Understanding the Atom: Fundamental Building Blocks

The atom is the smallest indivisible particle from which all matter is built. While all atoms are fundamental, they differ according to the specific element they constitute. Despite their small size, atoms contain several internal parts and particles. Historically, various models, such as those proposed by Thomson and Rutherford, attempted to explain atomic structure. We will focus on the most current and widely accepted model, the Bohr model.

The Atomic Nucleus: Protons and Neutrons

The central part of the atom is the nucleus, which contains two primary types of particles:

• Neutrons: Particles with no electric charge (charge = 0).
• Protons: Particles with a positive electric charge (charge = +1)

ZOE Impression Paste

Advantages: Good adhesion, adequate working time, requires no insulation to the plaster model, is fluid allowing copying of fine details, and is economical.

Disadvantages: The Eugenol is acidified, and some patients are allergic to eugenol.

Elastomers

Organic materials formed by weak interaction with polymer molecules, forming a three-dimensional network with elastic properties.

Mercaptan Elastomers

Elastic impression materials with mercaptan groups in the polymer chain, which when hardened, forms a semisolid paste.

Synonyms: Polysulphide rubber, synthetic rubber, tiocoles.

Commercial presentation: Pasta-pasta

Consistencies: Light, regular, heavy.

Chemical Composition:

Paste: Polysulfide polymer (base), titanium dioxide (filler) can... Continue reading "Dental Impression Materials: ZOE Paste & Elastomers" »

Chemical Reaction Rates: Fundamentals and Catalysis

Key Concepts in Chemical Kinetics

• Rate Law

  The speed of a reaction is directly proportional to the concentrations of the reactants raised to some exponent.

• Collision Theory

  This theory states that a greater concentration of reactants leads to more frequent collisions, thereby increasing the reaction rate.

• Reaction Profile

  A diagram that illustrates the progress or development of a chemical reaction.

Factors Influencing Chemical Reaction Rates

The speed of a chemical reaction depends on several critical factors:

• Nature of Reactants: The inherent properties of the reacting substances.
• Concentration: Higher concentrations generally lead to faster reactions.
• Physical State of Reactants: This factor involves

Key Concepts in Metallurgy and Materials Science

• The higher the ideal critical diameter of steel, the lower its hardenability.
• The greater the hardenability of steel, the greater the hardness of martensite that forms upon quenching.
• The lower the specific heat of a bath, the more energetic the cooling it produces during tempering.
• Examples of transformations include diffusion and martensitic transformations.
• Standard heat treatment can result in a coarser grain size in steels compared to those annealed at the same temperature.
• Hadfield steel, with more than 1% carbon and 14% manganese, is an example of martensitic steel.
• Magnesium is the element that causes the graphitization of white cast irons.
• Standard heat treatment produces a coarser grain size