Module 1: Properties + Structure of Matter

Mixture

• can be separated into pure substances

• Homogenous or heterogeneous

• Properties change as relative amounts of each substance change

• Varied composition

Pure substance

• Can’t be separated

• Homogeneous

• Constant properties (e.g. colour, density)

• Fixed composition

Impure substance

contaminated with other substances (mixture)

Homegenous

uniform composition

heterogeneous

non-uniform composition (irregular particles)

pure substances

elements/compounts

solution

homogeneous mixture, particles so small they don’t dissolve

suspension

heterogeneous, dispersion of particles that settle on standing

physical change

no new substance is formed (e.g. change of state, dissolving, separating)

chemical change

at least one new substance formed

sugns of chemical change

gas, precipitate forms, colour change, temp change, odor, solid disappears

physical properties

characteristics we can observe without changing into different substances (particle size, melting/boiling point, electrical conductivity, density, colour)

sedimentation + decantation

solids settle to bottom, liquid carefully poured off

separating dissolved solids

evaporation to dryness: liquid boiled off

crystalisation: solution becomes saturated, solute crystals form

distillation

solution boiled, vapour condesnced back into liquid + separated. 2 liquids can be separated if boiling points 40-50 degrees apart

fractional distillation

mixture of liquids separated through many distillations (when boiling points are close together)

separating funnel

immiscible liquids (don’t become homogeneous) separate into distinct layers, denser at the bottom. bottom liquid drained out

chemical properties

chemical changes/reactions a substance undergoes when exposed to other substances, heat or light (reaction with oxygen, water, acids/bases, decomposition)

properties of metal elements

solids at room temp, shiny/lustrous, conductors of heat + electricity, maleable + ductile

elements in the same group share

similar chemical properties due to same number of valence electrons

isotope

variants of an element that have the same number of protons but different number of neutrons (can change physical properties slightly)

orbital

volume of space surround nucleus of atom through which 1 or 2 electrons randomly move. each orbital accomodates 2 electrons

sublevels/subshells

each shell is split into sublevels/subshells. each subshell is made up of orbitals. subshells: s(2 electrons), p,(6 electrons) d(10 electrons), f (14 electrons). 1st level has s subshell, 2nd has s and p, 3rd has s, p, d, 2th has s,p,d,f

s orbital shape

spherical

p orbital shape

dumbell/double pear

orbital notation

1s¹ (1: energy level, s: sublevel, ¹: no of electrons in orbital

electron configuration sequence

1s

2s 2p

3s 3p

4s 3d 4p

5s 4d 5p

6s 4f 5d 6p

7s 5f 6d 7p

electron configuration sequence rule

d always 1 shell number behind, f always 2 behind

electron configuration shorthand

replace core shells with previous noble gas in brackets, then valence shell configuration (e.g. potassium: [Ar] 4s¹)

Carbon-12 scale

used to define all different types of relative mass, all elements mass is measured relative to the mass of carbon, which is 12

relative atomic mass

average mass of the isotopes present in the naturally occuring element

calculating relative atomic mass

relative isotopic mass x relative abundance + relative isotopic mass x relative abundance

relative molecular mass

add up relative atomic masses of each atom in molecule

relative formula mass

mass of repeating unit in a giant structure (used in ionic/ginat convalently bonded molecules)

Atomic emission spectroscopy

if we heat atoms to a high temperature (>1500°C), some electrons get excited out of their normal energy levels into higher energy levels, then after a short time, fall back to normal (ground) state. As they fall back to ground state, they release excess energy as visible, UV or infrared light (energy emitted = energy absorbed). The greater the amaound of energy released, the shorter the wavelength of radiation emitted (lots of energy = UV, medium = visible, low = infrared)

atomic emission spectrum

set of bright/coloured lines on black backgrounds representing different wavelengths emitted by atom, unqiue for each atom. Each line represents an electron that gets excited then emits photons of specific wavelengths. Some elements produce distinctive flame colours as one electron transition occurs more frequently than any others

flame colours

strontium: deep red, lithium: dull red, calcium: orange-red, sodium: yellow, barium: apple green, copper: blue-green, potassium: lilac

Bohr theory

electrons move around the nucleus in fixed orbits, when they absorb energy they move to larger radius orbits. electrons can only have certain discrete energies

Schrodinger theory

treated electrons as waves, they move at extremely high speeds + fairly randomly through orbitals around the nucleus. Lead to the idea of energy levels, sublevels + orbitals