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

1. Gold Extraction

   Gold is found mainly as the metal itself in the earth because it has a low reaction rate, which prevents easy oxidation.

Carbon Extraction of Zinc

Carbon can be used to extract zinc because carbon has a higher reaction rate than zinc.

Sodium Extraction

Sodium was not extracted until 1807 because sodium attaches itself very strongly to other elements, making it difficult to separate and obtain a pure substance.

Limestone

i) Name of Material: Limestone

Reason why this metal is used: It decomposes silicon dioxide in the heat of the furnace to calcium oxide.

ii) Word Chemical Equation for the Reaction of Iron Extracted from Iron Ore when a Gaseous Oxide of Carbon Reacts with Iron Oxide: FeO + CO = Fe + CO2

Aluminium Extraction

i) Why a Mixture... Continue reading "Extraction of Metals and Chemical Reactions" »

Matter Composition

- Matter: Formed of two or more pure substances.

Heterogeneous Mixtures

1. Heterogeneous: Non-uniform composition.

Homogeneous Mixtures

2. Homogeneous: Uniform composition, small particles.

Solutions

- Solution: Homogeneous mixture, small particles, liquid solutions are transparent.
- Solute: Smaller amount.
- Solvent: Larger amount, often water (aqueous).

Colloids

- Colloid: Mixtures with larger particles.

Electrolytes

- Electrolytes: Allow water to conduct electricity due to ions in the solution. Strong electronegativity.
Examples:
- Acids: HCl, HNO₃, H₂SO₄
- Salts: K⁺, Na⁺, NH₄⁺, NO₃^-
Example of Dissociation:
NaCl → Na⁺ + Cl^-

Non-Electrolytes

- Molecules, polar for H₂O, sugars; polar solute dissolves in a polar solvent.

Hydrogen Bonding

-... Continue reading "Matter, Solutions, and Gases: Chemistry Fundamentals" »

Preliminary Test

Systematic Analysis for Anions

To separate crude oil into its fractions, we use fractional distillation. This process occurs in an oil refinery. The crude oil is heated to about 350 degrees Celsius in a column that gets cooler higher up. Each fraction will evaporate and rise up the column until it reaches a part that is cool enough to condense it. The liquid goes into its respective tube and is separated from the rest of the crude oil. The smallest alkanes, which have a lower boiling point, will rise to the top. The largest fraction, bitumen, never evaporates and falls as a liquid to the bottom.

Cracking

Crude oil contains a mix of alkanes. Shorter alkanes are the most useful as fuels. We can obtain more shorter alkanes by breaking down the larger ones. This process is called... Continue reading "Fractional Distillation and Cracking Polymers: Separating Crude Oil" »

Chemical Bonding in Dental Materials

Primary Bonds

Factors Influencing Material Properties:

1. Type of bond between atoms and molecules
2. Inter-atomic distance
3. Atomic packing

Matter: Any substance that has mass and occupies space.

Atom: The fundamental unit of matter, consisting of a central nucleus (protons and neutrons) surrounded by electrons.

Types of Primary Bonds:

• Ionic Bond: Attraction between positive and negative ions. Characteristics: Strong, heat resistant, insulator, insoluble in organic solvents, basic bond in ceramics.
• Covalent Bond: Sharing of electrons between two atoms. Characteristics: Strong, insulator, water insoluble, basic bond in polymers.
• Metallic Bond: Attraction between positive atomic cores and free electrons. Characteristics: High

Basic Definitions of Matter

• Mass: The amount of matter an object has.
• Volume: The amount of space a substance occupies.
• Density: The relation of the amount of mass in a given volume.
• Matter: Anything that has mass and volume.
• Inertia: The tendency of an object to resist a change in motion.
• Weight: The action of gravitational force on an object.

Units of Measurement

• Newtons (N): A unit of force.
• 1 N = 100 g
• 1 kg = 1000 g

Properties of Matter

Chemical Properties

• A material's property that becomes evident during or after a chemical reaction.
• Examples: Flammability, reaction with O₂ (oxygen).

Physical Properties

• Observed or measured without changing the composition of matter.
• Examples: State, density, solubility, malleability, shape.

Changes in Matter

Chemical

Classification of Crystalline Solids

In crystalline solids, the atoms, ions, or molecules are held together by various types of cohesive forces, which may be chemical bonds or intermolecular forces. Based on the nature of bonding between their constituent particles, crystalline solids are classified into distinct types.

Ionic Crystals

Ionic crystals are formed by the interaction of positive and negative ions. These ions are held together by strong electrostatic forces of attraction, also known as ionic bonds. Examples include NaCl, KNO₃, Na₂CO₃, and K₂Cr₂O₇.

Properties of Ionic Crystals

• They occur in the solid state at room temperature.
• They have a distinct geometrical shape due to the close packing of cations and anions.
• They are very hard.
• They are

Essential Laws and Principles in Science

Avogadro's Law

Equal volumes of gases under identical temperature and pressure conditions will contain equal numbers of particles (atoms, ions, molecules, electrons, etc.).

Boyle's Law

At constant temperature, the volume of a confined gas is inversely proportional to the pressure to which it is subjected.

PV = k

Charles' Law

At constant pressure, the volume of a confined gas is directly proportional to the absolute temperature.

V = kT

Combining Volumes

Refer to Gay-Lussac's Law.

Conservation of Energy

Energy can be neither created nor destroyed; the energy of the universe is constant. This is the First Law of Thermodynamics.

Conservation of Mass

Also known as Conservation of Matter. Matter can be neither created nor... Continue reading "Fundamental Laws of Chemistry and Physics Explained" »

Temperature Conversions

• Celsius to Fahrenheit: F = (9/5) * C + 32
• Celsius to Kelvin: K = C + 273

Atomic Structure

• Atomic Mass: Protons + Neutrons (upper left symbol)
• Atomic Number: Protons (bottom left symbol)

Quantum Mechanics

• Planck's Constant (h): 6.6260755 x 10^-34 J*s
• Energy of a Photon: E = hv or E = hc / wavelength

Electronic Transitions

• Absorption: When energy is absorbed by an atom, an electron is excited to a higher energy level or orbital.
• Emission: When an electron relaxes from a higher energy orbital to a lower one, it emits a photon.

Filling Orbitals

s = 2, p = 6, d = 10, f = 14

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f

Periodic Trends

• Atomic Radius: Increases down a group and decreases across a row.
• Ionization Energy: Amount of energy