Introduction to Matter and Properties

• A pure substance contains only one kind of matter and can be an element or a compound
• Boiling point refers to the temperature at which a liquid's vapour pressure equals the external (atmospheric) pressure
• Chromatography is a method of separating and identifying certain substances
• A compound consists of two or more different elements
• Density is the mass per unit volume of a substance
• A heterogeneous mixture contains components that can be easily identified, like sand and water
• A homogeneous mixture has a uniform composition, such as a solution of salt and water
• An electrical conductor allows the flow of charge
• An electrical insulator does not allow the flow of charge
• An element is a pure chemical substance with only one type of atom
• Metalloids/semi-metals have properties intermediate between metals and non-metals
• Melting point is the temperature at which a solid changes to the liquid phase
• A pure substance cannot be separated into simpler pieces by physical methods
• A thermal conductor allows heat to pass through easily
• A thermal insulator does not allow heat to pass through easily

Boiling Point Details

• Boiling point is the temperature at which a liquid's vapour pressure equals the external atmospheric pressure
• Boiling points are lower at higher altitudes due to lower atmospheric pressure
• Water's boiling point at sea level is 100 °C but is 71 °C at the top of Mount Everest

Brownian Motion

• Brownian motion is the random movement of microscopic particles suspended in a liquid or gas

• It is caused by collisions between these particles and the molecules of the liquid or gas

• The movement is named after Scottish botanist Robert Brown (1773-1858)

• Condensation is the process where a gas or vapour changes to a liquid, either by cooling or increased pressure

• Deposition is a process in which a gas transforms directly into a solid

• Diffusion is the movement of atoms or molecules from an area of higher concentration to an area of lower concentration

• Evaporation is the change of a liquid into a vapour at a temperature below the boiling point at the surface of a liquid

• Freezing is the process during which a liquid changes to a solid by the removal of heat

• Freezing point is the temperature at which a liquid releases sufficient heat and becomes a solid

• Melting is the process during which a solid changes to a liquid by the application of heat

Melting Point Defined

• Melting point is the temperature at which a solid, given sufficient heat, becomes a liquid
• For a given substance, the melting point of its solid form is the same as the freezing point of its liquid form and depends on purity and surrounding pressure
• Sublimation is the process during which a solid changes directly into a gas without passing through an intermediate liquid phase

Atomic Structure

• Atomic number (Z) refers to the number of protons in the nucleus of an atom
• Atomic orbital is the most probable region around the nucleus where electrons are located
• Electrons are negative particles occupying space around the nucleus
• Excited state describes when an electron gains energy and moves into a higher energy level
• Ground state refers to the lowest energy state of an electron
• Hund's rule specifies no pairing in p orbitals before there is at least one electron in each p orbital
• Ionisation energy is the energy needed to remove an electron(s) from an atom in the gaseous phase
• Isotopes are atoms of the same element with the same atomic number but different mass numbers due to a difference in the number of neutrons
• Mass number (A) is the sum of protons and neutrons in the nucleus
• Neutrons are neutral particles in the atomic nucleus
• Nucleons are the particles in the nucleus of an atom, i.e., protons and neutrons
• Pauli's exclusion principle limits a maximum of two electrons per orbital, provided they spin in opposite directions
• Protons are positive particles in the atomic nucleus
• Quantised energy level describes an energy level that can only have specific amounts of energy
• Relative atomic mass is the mass of an atom of an element on a scale where carbon-12 has a mass of 12
• Valence electrons are outer electrons; electrons in the highest filled energy level of an atom

Atomic Properties

• Atomic number is the number of protons in the nucleus of an atom
• Atomic radius measures the radius of an atom from the atomic nucleus to the outermost stable electron in an atom
• Boiling point refers to the temperature of a liquid at which its vapour pressure equals the external (atmospheric) pressure
• Density is the mass per unit volume of a substance
• Electron affinity is the energy released when an electron is attached to an atom or molecule to form a negative ion
• Electronegativity is the tendency of an atom in a molecule to attract bonding electrons closer to itself
• First ionisation energy is the energy needed to remove the first electron from an atom in the gaseous phase
• A group is a vertical column in the periodic table; some groups have names
• An ion is a charged particle made from an atom by the loss or gain of electrons
• Ionisation energy is the energy needed to remove an electron(s) from an atom in the gaseous phase
• Melting point is the temperature at which a solid, given sufficient heat, becomes a liquid
• A period is a horizontal row in the periodic table

Chemical Properties

• Periodicity is the repetition of similar properties in chemical elements, as indicated by their positioning in the periodic table
• Transverse Pulse is a wave pulse where the particles of the medium move perpendicular to the direction of the wave's propagation
• Amplitude is the maximum disturbance of a particle from its rest position due to the pulse
• Pulse Length is the distance over which a pulse extends
• Constructive Interference happens when the displacements of pulses are in the same direction, adding together for a larger amplitude
• Destructive Interference happens when displacements of pulses are in opposite directions, subtracting from each other
• Superposition occurs when two or more pulses/waves meet at a point, resulting in a displacement that is the sum of the displacements of the individual pulses/waves