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Updated Apr 1, 2026

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5 pages

Foundations of Chemistry: Annotated Guide

susie powell

@susiepowell_

Chemistry is the fascinating science that explores the composition, properties,... Show more

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# 1 Principles of chemistry

The following sub-topics are covered in this section.

(a) States of matter

(b) Elements, compounds and mixtur

States of Matter and Their Properties

Matter exists in three main states: solid, liquid and gas. In solids, particles are arranged in a fixed, regular pattern, vibrating in place with little energy. Liquids have particles with some energy that take the shape of their container's bottom. Gases contain particles with high energy moving randomly with no fixed shape.

These states can transform through processes like melting (solid to liquid), freezing (liquid to solid), evaporation (liquid to gas), and condensation (gas to liquid). Less common transitions include sublimation (solid directly to gas) and deposition (gas directly to solid). These changes involve adjustments in the arrangement, movement, and energy of particles.

When substances dissolve, we get solutions consisting of a solute (the substance that dissolves) and a solvent (the liquid that does the dissolving). A saturated solution occurs when no more solute can dissolve. Solubility is measured in grams per 100g of solvent and varies with temperature.

Did you know? You can create your own solubility curve by measuring how much of a compound dissolves at different temperatures. This is exactly what scientists do to understand how substances behave in solution!

Elements, Compounds and Mixtures

Everything around us can be classified as an element, compound, or mixture. Elements contain only one type of atom, while compounds have two or more types of atoms chemically bonded together. Mixtures contain two or more substances that aren't chemically joined.

You can identify a pure substance by its fixed melting and boiling point. For example, pure water should boil at exactly 100°C. If it boils over a range of temperatures, it's a mixture. This knowledge is crucial for determining the purity of substances in science labs.

Scientists use various separation techniques to isolate components in mixtures. These include simple distillation (separating based on boiling point), filtration (removing solid particles), crystallisation (evaporating to leave crystals), and paper chromatography (separating coloured chemicals). In chromatography, we can calculate Rf values to identify specific components.

Try this! Next time you use coloured pens, try this experiment: draw a small dot of each colour on filter paper and dip the edge in water. Watch how different pigments in each ink travel different distances, revealing that many "single colours" are actually mixtures!

Atomic Structure and Chemical Calculations

The fundamental building blocks of matter are atoms (particles that uniquely define an element) and molecules (groups of atoms bonded together). Each atom consists of protons, neutrons, and electrons with specific positions, relative masses, and charges.

An element's atomic number equals the number of protons in its nucleus, while the mass number equals the sum of protons and neutrons. Isotopes are atoms of the same element with different numbers of neutrons. The relative atomic mass (Ar) is calculated using the abundance of an element's isotopes.

Chemical equations use symbols to represent reactions. You'll need to balance them to show that matter is conserved. Use state symbols (s, l, g, aq) to indicate whether substances are solid, liquid, gas or in aqueous solution. The relative formula mass (Mr) is found by adding the relative atomic masses of all atoms in a compound.

Remember: The mole is a crucial unit in chemistry representing 6 × 10^23 particles. The formula mass in grams = 1 mole. This relationship is key for calculating quantities in chemical reactions!

Chemical Bonding: Ionic and Covalent

Atoms bond to achieve stable electron configurations. Ionic bonding occurs between metals and non-metals through electron transfer. Metals lose electrons to become positively charged ions, while non-metals gain electrons to become negatively charged ions. The strong electrostatic attraction between these opposite charges forms the bond.

Compounds with giant ionic lattices have high melting and boiling points because substantial energy is needed to overcome the strong electrostatic forces. Ionic compounds don't conduct electricity when solid (ions fixed in place) but do conduct when molten or dissolved (ions free to move).

Covalent bonding happens between non-metals when atoms share electron pairs. The electrostatic attraction between positively charged nuclei and negatively charged shared electrons forms the bond. Substances with simple molecular structures have low melting and boiling points since little energy is needed to overcome the weak intermolecular forces between molecules.

Understanding structures: Carbon forms three fascinating structures with very different properties. Diamond (hard, insulating) has each carbon forming 4 bonds in a rigid 3D structure. Graphite (soft, conducting) has carbon in layers with 3 bonds each. C60 fullerene forms hollow sphere-like molecules. These differences perfectly demonstrate how structure determines properties!

Metallic Bonding and Electrolysis

Metallic bonding occurs between metal atoms, where outer shell electrons become delocalized and free to move throughout the lattice. The positive metal ions are held in a regular arrangement by attraction to this "sea" of negative electrons. This explains why metals conduct electricity $free-moving electrons$ and are malleable (layers can slide over each other without breaking bonds).

Electrolysis is the process of using electricity to split up compounds. In this process, anions (negative ions) are attracted to the anode (positive electrode), while cations (positive ions) are attracted to the cathode (negative electrode). Ionic compounds conduct electricity only when molten or in solution because ions need to move freely.

During electrolysis of molten compounds, the metal ions gain electrons at the cathode to form the metal, while non-metal ions lose electrons at the anode to form molecules. In aqueous solutions, things get more complicated because water molecules provide additional ions $H+ and OH-$ . The least reactive ions are discharged first.

Application alert: Electrolysis isn't just classroom science—it's used industrially to extract reactive metals like aluminium, purify copper for electrical wiring, and electroplate metals to provide protective or decorative coatings. This process demonstrates chemistry's real-world importance!

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Chemistry

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266

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Updated Apr 1, 2026

•

5 pages

Foundations of Chemistry: Annotated Guide

susie powell

@susiepowell_

Application alert: Electrolysis isn't just classroom science—it's used industrially to extract reactive metals like aluminium, purify copper for electrical wiring, and electroplate metals to provide protective or decorative coatings. This process demonstrates chemistry's real-world importance!