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

Dalton's Atomic Theory

John Dalton proposed that elements were made up of little solid spheres without internal structure. Atoms of the same element were equal. Atoms combine, forming compounds. Depending on the ratio, we can have different compounds.

J.J. Thomson

First model of the atom (1904). He discovered/proved the existence of tiny, negatively charged particles: electrons.

Rutherford's Model of the Atom

Gold foil experiment, Ernest Rutherford (1911). Alpha particles are tiny, positively charged particles much smaller than an atom. An atom is mostly empty space. Some particles will bounce back, and some others will pass but in a different way. The nucleus is something dense and positively charged.

Thomson's Atomic Model

In 1904, Thomson's atomic... Continue reading "Dalton's Atomic Theory and the Evolution of Atomic Models" »

Chemical Reactions

occurring at low temperatures are
                _______low______ than reaction rates of chemical reactions occurring at high
temperatures.

40. Increasing pressure causes gas particles to             ______collide_______________. This
                ________increases______________ the reaction rate of a chemical reaction.

41. All reactions require    ___activation energy___________ for chemical bonds to begin breaking.

Exercise 3 – Analyzing the Financial Impact of Price and Volume Changes on Apple iPhones

Apple iPhone Sales and Manufacturing Costs

In 2014, Apple sold approximately 150,000,000 iPhones at a price of $640 per unit. The company's average manufacturing cost per iPhone is detailed in Table 1.

Table 2 outlines Apple's fixed costs associated with its iPhone business.

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" »

Fundamental Chemical Principles

Reactivity Trends in Groups I and VII

• Group I (Alkali Metals): Reactivity increases down the group.
  • Their atoms lose their outer electron to achieve a stable electron shell.
  • As the number of electron shells increases, the outer electron is further from the positive nucleus, making it easier to lose.
• Group VII (Halogens): Reactivity decreases down the group.
  • Their atoms gain or share an electron to achieve a stable electron shell.
  • The positive nucleus of the atom attracts the extra electron.
  • As the number of electron shells increases, the outer shell is further from the nucleus, making it more difficult to attract an electron.

Common Ores and Alloys

• Iron Ore: Hematite
• Aluminum Ore: Bauxite
• Sodium Ore: Rock Salt
• Lead Ore: Galena
• Zinc

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