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

1. True or False Statements

a) True

b) True

c) True / FALSE, if the hypothesis has not been demonstrated.

2. Measurement Units and Properties

a) Size: m³ is a unit of volume and can be used in moderation.

b) Scalability: It does not scale; it is not a unit of restraint.

c) Magnitude Measurement: Magnitude can be measured in K (Kelvin).

3. Units of Measurement

• Length - Meter - m
• Mass - Kilogram - kg
• Time - Second - s
• Temperature - Kelvin - K
• Intensity of Current - Ampere - A

4. Unit Conversions

a) 2.5 mm x (1 m / 1,000 mm) = 0.0025 m = 2.5 x 10^-3 m

b) 0.53 mg x (1 g / 1,000 mg) x (1 kg / 1,000 g) = 0.00000053 kg = 5.3 x 10^-7 kg

c) 3 h x (3,600 s / 1 h) = 10,800 s = 1.08 x 10⁴ s

5. Calculations with Significant Figures

a) 8.34 x 3.1456 = 26.234304 = 26.2

b) 4.00... Continue reading "Understanding Physical Quantities and States of Matter" »

Introduction to Chemistry

Chemistry is the science of matter and its properties, including its composition, structure, physical properties, and reactivity. It involves observation, knowledge, and reasoning to deduce general principles and laws.

Types of Chemistry

1. Experimental:

• Natural: Physics, Chemistry, Biology
• Human: Geography, Politics, History

Formal: Mathematics and Logic

The scientific method involves observation, gathering information, forming a hypothesis, conducting experiments (with independent, dependent, and control variables), analyzing results, and developing a theory or law.

Conversions:

• 1 lb = 0.454 kg
• 1 in = 2.54 cm
• 1 in² = 6.45 cm²

Chemical Compounds

• Hydroacids (H + NM)
• Binary Salts (M + NM)
• Hydrides (M + H)
• Non-metal Oxides (NM + O)
• Metal

... Continue reading "Understanding Chemistry: Formulas, Reactions, and Concepts" »

Planck's Theory

The energy emitted by radiation is directly proportional to the frequency of radiation.

Bohr Model

Postulates:

1. Electrons revolve around the nucleus in circular orbits without emitting energy.
2. Electrons are only allowed in orbits where their angular momentum is a multiple of h/2π.
3. When an electron moves between orbits, the energy difference is emitted as radiation.

Bohr determined the radius, energy, and location of electrons within these orbits.

Sommerfeld's Modifications

Sommerfeld modified the Bohr model to include elliptical orbits. He introduced a second quantum number, which depends on the first and describes the orbit's shape.

l = 0 ... (n-1)

Zeeman Effect: When an atomic spectrum is subjected to a magnetic field, spectral lines... Continue reading "Atomic Structure and Quantum Mechanics" »

Fundamental Concepts of Mixtures

Heterogeneous Mixtures

Do not present a uniform appearance to the naked eye. Their components are visibly distinct.

Homogeneous Mixtures (Solutions)

Present a uniform appearance to the naked eye. Their components are indistinguishable, even with a microscope.

Colloids

Mixtures that appear uniform to the naked eye but whose components can be distinguished with a microscope.

Dissolution (Solution Formation)

The process of forming a homogeneous mixture where a major component (the solvent) dissolves one or more other substances (the solutes).

Concentration

A measure indicating the amount of solute dissolved in a given quantity of solvent or solution.

Solubility

The maximum quantity of a substance (solute) that can be dissolved... Continue reading "Chemistry Mixture Separation Methods and Definitions" »

Fundamental Concepts of Atomic Structure

• Atomic Orbital: The region of space around the nucleus in which there is a high probability of finding an electron with a particular energy.
• Effective Nuclear Charge ($Z_{eff}$): The net positive charge experienced by an electron in a multi-electron atom. It is the charge the core would have if the atom consisted only of the core and the electron considered.
• Screening (Shielding): The repulsion between electrons, which reduces the nuclear attraction experienced by outer electrons and affects their energy state.

Rules Governing Electronic Configuration

The fundamental electronic configuration is determined by three key principles:

1. Aufbau Principle (Rule of Construction): Electrons fill available atomic orbitals

... Continue reading "Atomic Structure Principles and Periodic Property Trends" »

Understanding Atoms: Key Concepts

Atom: The smallest unit of a chemical element that retains its identity and properties, and cannot be split by chemical processes.

Mass Number: Represents the sum of protons and neutrons present in the atomic nucleus. Also known as the nucleon number.

Atomic Number: The positive integer that equals the total number of protons in an atom's nucleus.

Ion: A particle formed when a neutral atom or group of atoms gains or loses one or more electrons.

Cation: An ion (either atom or molecule) with a positive electric charge.

Anion: An ion (either atom or molecule) with a negative electric charge.

Isotope: Used to indicate that all isotopes of the same element are found in the same place in the periodic table.

Atomic Mass:... Continue reading "Understanding Atoms: Mass, Number, Ions, and Isotopes" »

States of Matter and Their Changes

State changes are processes experienced by the body according to the environmental conditions of pressure and temperature.

• Solid-Liquid (Fusion)
• Liquid-Gas (Vaporization)
• Gas-Solid (Deposition)
• Liquid-Solid (Solidification)
• Solid-Gas (Sublimation)
• Gas-Liquid (Condensation)

When heating a body, the energy of the particles increases. There comes a moment when this energy is sufficient to overcome the forces of cohesion, and then fusion occurs when we consider that part of a solid body. The same applies to all states of aggregation. The form of fusion of a body depends on its nature. We will distinguish between crystalline and amorphous bodies.

• In a crystalline body, such as ice, melting is produced at a constant temperature

... Continue reading "Understanding Matter: States, Changes, and Mixtures" »

Chemical Elements

These are the fundamental building blocks from which all matter is composed.

Chemicals

This is a substance that cannot be separated into its components by physical processes.

Alloys

Artificial mixtures made from two or more chemical elements or compounds.

Composites

Composite materials made from two or more components that have very different physical and chemical properties, and which together form a substance with properties different from those of its separate components.

Metal Extraction System

Metals are obtained basically by two industrial processes: heat or electricity. In both processes, this is done via a chemical reaction called reduction, in which the pure metal is obtained by separating it from the compound where it is... Continue reading "Key Concepts in Materials and Nanotechnology" »

Dalton's theory, which posited atoms as indivisible particles, was eventually superseded by experiments revealing the electrical properties of matter. These groundbreaking studies demonstrated that atoms themselves contain smaller, subatomic particles responsible for electrical behavior: the electrons.

Early Atomic Theories and Electron Discovery

Thomson and the Electron

Towards the end of the 19th century, J.J. Thomson conducted groundbreaking experiments using cathode ray tubes (discharge tubes with a positive and a negative pole across which an electric current passed). He discovered a negatively charged particle within the atoms of chemical elements, which he named the electron. When an electrical discharge occurred between the plates, a beam... Continue reading "Atomic Structure Explained: Subatomic Particles & Key Models" »

Chemical Bonding Fundamentals

Chemical bonding describes how atoms or ions join to form molecules, giant structures, or lattices.

The Octet Rule

Atoms that bond tend to gain, lose, or share electrons until they complete their valence shell with eight electrons.

Primary Types of Chemical Bonds

• Ionic Bonding

  Originates from the electrostatic forces between oppositely charged ions, resulting in the formation of an ionic crystal.

• Covalent Bonding

  Originates when atoms share electrons so that their valence shells are filled, thereby satisfying the octet rule.

Models and Theories of Bonding

• Lewis Model

  The bond is established when attractive forces between atoms are balanced by repulsive forces.

• Standard Electronic Clouds Model

  The charge density between the

... Continue reading "Chemical Bonding: Forces, Structures, and Molecular Properties" »