Study guide: Foundations of Chemistry

📋 Course Outline

1. Chemistry and Physical Changes
2. Matter, Mass, and Energy
3. Substance Types and Mixtures
4. Methods for Separating Mixtures
5. Pure Substances and Chemical Reactions
6. Elements and Chemistry’s Origins
7. Laws of Chemical Combination
8. Dalton’s Atomic Theory
9. Gas Volumes and the Mole

📖 1. Chemistry and Physical Changes

🔑 Key Concepts & Definitions

• Chemistry: Studies the composition, properties, and internal structure of substances, as well as their changes and the mechanisms of reactions.

★ Must-know

📌 A chemical change alters a substance’s composition and produces a substance that is no longer the same, whereas a physical change alters energy or aggregate state without changing composition.

Further detail

• Physics studies the state of substances, energy, and energy transformations, while chemistry and physics overlap because chemical reactions involve energy changes.

• Heating platinum wire makes it glow and emit light without changing platinum’s characteristic properties, so the change is physical.

• Heating magnesium wire makes it glow and burn into white magnesium oxide, so the physical heating is accompanied by a chemical change.

• Major branches of chemistry include:

  • inorganic chemistry
  • organic chemistry
  • general chemistry
  • analytical chemistry
  • biochemistry
  • chemical technology

💡 Memory Hook

Platinum glows but stays platinum; magnesium becomes magnesium oxide.

📖 2. Matter, Mass, and Energy

🔑 Key Concepts & Definitions

• Mass: A basic property of matter measured in kilograms.

★ Must-know

📐 Formula - The relation between weight force, mass, and gravitational acceleration is $F=mg$.

📐 Formula - The gravitational force between two bodies is proportional to the product of their masses and inversely proportional to the square of their separation: $F=k\frac{m_1m_2}{r^2}$. - Њутновиот закон (Isak Newton, 1642–1727), 1642–1727

📐 Formula - Einstein’s mass–energy relation is $E=mc^2$, where energy is measured in joules, mass in kilograms, and the speed of light is $c=2.9979\cdot10^8\,\mathrm{m/s}$. - Алберт Ајнштајн (Albert Einstein, 1879–1955), 1905

Further detail

• Earth’s gravitational acceleration is given as $g=9.8\,\mathrm{m/s^2}$, so the force ratios of different substances equal their mass ratios.

📐 Formula - The kinetic energy of moving matter is $E_{\mathrm{kin}}=\frac{mv^2}{2}$.

• According to the course’s account of Einstein’s theory, the mass associated with energy is $m=E/c^2$, and matter in motion has greater mass than it does at rest. - Ајнштајн

• Fission of 1 kg of uranium-235 releases $8.23\cdot10^{13}\,\mathrm{J}$, equivalent to 0.915 g of mass, or about 0.1% of the uranium’s mass.

💡 Memory Hook

Motion increases energy, and energy contributes to mass.

📖 3. Substance Types and Mixtures

🔑 Key Concepts & Definitions

• Homogeneous Substance: Consists of a single kind of matter and has a uniform composition.
• Heterogeneous Substance: Consists of more than one kind of matter, such as granite, which contains quartz, feldspar, and mica.
• Pure Substance: Has a precisely defined, constant chemical composition and characteristic constant properties.
• Mixture: Contains two or more substances in a variable proportion, and each component retains its characteristic properties.

📝 Essential Points

• Pure gold is described as having a density of 19.3 g/cm³ and a melting point of 1,049 °C, with a yellowish luster and no impurities.

• A mixture’s properties depend on the amounts and properties of its components and can be determined by suitable experiments.

• Homogeneous mixtures include:

  • solutions
  • solid crystalline mixtures such as alloys
  • gas mixtures such as air

• Brass is a solid mixture of copper and zinc, steel consists of iron and carbon, and bronze is a mixture of copper and tin.

📖 4. Methods for Separating Mixtures

🔑 Key Concepts & Definitions

• Sublimation: The direct transition between solid and gaseous states and can separate substances that sublime from those that do not.
• Chromatography: Separates pure substances from homogeneous mixtures based on differences in volatility and adsorption.

★ Must-know

• Mixtures can be separated into their components by heating and condensing vapour, dissolving soluble components and then filtering or crystallizing, separating liquids by boiling point, and filtering solid–liquid mixtures.

• Distillation separates more volatile substances from liquid solutions, leaving less volatile substances behind.

Further detail

• Centrifugation is a separation method that uses centrifugal force.

• The source describes filtration as separating colloidal particles sized 1 nm to 1 μm from dissolved particles, which pass through the membrane’s fine pores.

• Flotation separates hydrophobic solids from hydrophilic solids by using bubbles that carry hydrophobic particles to the surface.

• Fractional distillation gradually separates substances whose boiling points are very close.

• In distillation of a liquid mixture, vapours of the most volatile substances condense first.

• Fractional crystallization separates substances that crystallize from a solution, and dissolving and crystallizing the obtained crystals again is called recrystallization.

• Fractional dissolution separates substances that have different solubilities.

• Fractional diffusion separates gas mixtures because lighter molecules diffuse faster than heavier molecules.

• At the same temperature, the source states that light and heavy molecules have equal kinetic energy, so their speeds vary inversely with the square root of their masses.

• Thermodiffusion separates gas mixtures by concentrating the light component near a heated surface and the heavy component near a cold surface; in a vertical tube, the light component collects above the heavy component.

📖 5. Pure Substances and Chemical Reactions

🔑 Key Concepts & Definitions

• Analysis: The chemical decomposition of a compound into elements.
• Synthesis: The chemical combination of elements to form a compound.

★ Must-know

• Characteristic physical properties include:

  • color
  • odor
  • aggregate state
  • melting point
  • boiling point
  • solubility

• Chemical properties of pure substances are determined through reactions that transform them into other substances.

📌 Elements are pure substances that cannot be decomposed into other substances by chemical reactions, whereas compounds can be decomposed into elements by chemical reactions.

Further detail

• A pure substance’s definite melting point can help identify its composition and assess its purity.

• Mercury oxide can be decomposed by analysis into mercury and oxygen, and mercury and oxygen can combine by synthesis to form mercury oxide.

💡 Memory Hook

Analysis breaks compounds apart; synthesis joins elements.

📖 6. Elements and Chemistry’s Origins

★ Must-know

• Robert Boyle’s 1661 book The Sceptical Chymist gave an early definition of an element as a basic substance that cannot be decomposed into simpler substances or formed from simpler substances. - Бојл (Robert Boyle, 1627–1697), „Скептичен хемичар“

Further detail

• About 110 chemical elements occur in nature and that others are obtained in laboratories.

• According to F. W. Clarke, 92 elements occur in Earth’s crust, and oxygen and silicon together make up half of the crust. - Кларк (F. W. Clarke)

📖 7. Laws of Chemical Combination

🔑 Key Concepts & Definitions

• Equivalent Mass: Benjamin Richter - Equivalent masses are the masses of elements that enter into a reaction, and elements combine in compounds in proportion to their equivalent masses.

★ Must-know

• The law of conservation of mass states that the total mass of all substances involved in a chemical reaction does not change. - Antoine de Lavoisier (1743–1794), XVIII vek

• Proust’s law of constant proportions states that a given chemical compound always contains its elements in a constant mass ratio. - Joseph Louis Proust (1754–1826), 1799 god.

• Dalton’s law of multiple proportions states that when two elements form multiple compounds, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers. - John Dalton (1766–1844), 1802 god.

Further detail

📌 Landolt’s statement says that in a closed system from which energy cannot escape, the sum of the amount of matter and energy, or their masses, remains constant. - Hans Landolt (1831–1910)

• The stated mass composition of water is 11.11% hydrogen and 88.89% oxygen.

📌 Daltonides are compounds with constant chemical composition, whereas Berthollides are compounds with variable chemical composition.

• The listed nitrogen-to-oxygen mass combinations are:
  • N₂O: 14:8
  • NO: 14:16
  • N₂O₃: 14:24
  • NO₂: 14:32
  • N₂O₅: 14:40

📌 Richter’s law of equivalent masses states that masses of two elements that react separately with the same mass of a third element also react with one another and with a definite mass of a fourth element. - Benjamin Richter (1762–1807), 1789 god.

📐 Formula - The course gives the relation $\frac{m_1}{m_2}=\frac{E_1}{E_2}$ and defines equivalent mass as $E_{\mathrm{eq}}=\frac{A}{\mathrm{valency}}$.

📖 8. Dalton’s Atomic Theory

📝 Essential Points

• Dalton’s atomic theory describes atoms as extremely small particles that cannot be divided during chemical reactions. - Далтон

• Dalton’s theory states that atoms of the same element are identical in mass, size, and chemical properties, while atoms of different elements differ in these properties. - Далтон

• Dalton’s theory states that compounds contain atoms of more than one element, with a fixed number of atoms of each element in each compound. - Далтон

• Dalton’s theory describes a chemical reaction as the separation, combination, or rearrangement of atoms, which are neither created nor destroyed in the reaction. - Далтон

📖 9. Gas Volumes and the Mole

🔑 Key Concepts & Definitions

• Mole: An amount of substance containing as many particles or groups of particles as there are atoms in 0.012 kg of carbon-12.

★ Must-know

📌 Gay-Lussac’s law states that reacting or produced gas volumes are in ratios of small whole numbers when measured at constant temperature and pressure. - Joseph Louis Gay-Lussac (1778-1850), 1805 год.

Further detail

• Two volumes of hydrogen react with one volume of oxygen to produce two volumes of water vapour.

• One volume of hydrogen reacts with one volume of chlorine to produce two volumes of hydrogen chloride.

• Three volumes of hydrogen react with one volume of nitrogen to produce two volumes of ammonia.

📊 Synthesis Tables

Substance Classification

Category	Composition	Examples
Pure substance	Fixed, definite composition	Gold; sodium chloride
Homogeneous mixture	Two or more pure substances, uniform mixture	Solutions; alloys; air
Heterogeneous substance	More than one kind of matter	Granite; blood; soil