Unit 1: Particulate nature of matter

Elements

• all substances are made up of one or more elements

• over 100 known elements

• the smallest part of an element is called an atom

Compounds

• contains more than one element combined chemically in a fixed ratio

• eg. water (two hydrogen atoms and one oxygen atom)

• compounds have varying chemical and physical properties from their respective component elements

Mixtures

• components may be elements or compounds

• are not chemically bonded together

  • retain individual properties

• all in the same stage = homogeneous

• eg. air

States of Matter

Solid state

• fixed shape and volume

• particles held together by intermolecular forces

• particles will vibrate at a fixed point but do not have translational velocity

• turns into gaseous state by sublimation

• turns into liquid state by melting

Liquid state

• fixed volume

• takes up the shape of the container

• held together by intermolecular forces

• turns into solid state by freezing

• turns into gaseous state by boiling/vaporization/evaporation

Gaseous state

• takes the space to completely fill container

• widely spaced particles

• intermolecular forces between particles are negligible

• pressure is due to gaseous particles colliding with the walls of the container

• turns into liquid state by condensation

• turns into solid state by deposition

Unit 2: The mole concept and chemical formulas

Avogadro’s Constant

• a single atom of an element has a small mass

• this mass is known as Avogadro’s constant (N_A)

• the mass of one mole of any substance is known as the molar mass (M)

• relative atomic mass (A): weighted mean of all the naturally occurring isotopes of the element

  • find the average

  • for molecules: relative molecular mass

  • for ionic compounds: relative formula mass

Formulas of Compounds

• empirical formula: in simplest whole number the ratio of atoms of each element in a substance

  • obtained by knowing the mass of each element

• molecular formula: shows the actual number of atoms in a substance

• structural formula: shows the arrangement of atoms and bonds within a molecule

Unit 3: Chemical reactions and equations

Properties of Chemical Reactions

• new substances are formed

• bonds are broken and formed resulting in an energy change

• fixed relationship between the number of particles and reactants

Chemical Equations

• reactants are written on the left hand side

• products are written on the right hand side

• number of moles of each element must be the same on both sides in a balanced chemical equation'

• single arrow shows reaction goes to completion

• state symbols

  • s = solid

  • l = liquid

  • g = gas

  • aq = aqueous solution

• coefficient refers to the number in front of the reactants and products in the equation

  • shows information on the molar ratio

Ionic Equations

• ionic compounds completely dissociate in solution

• spectator ions do not need to be written in the reaction

Unit 4: Mass and gaseous volume relationships

Measurement of molar quantities

• solids: measure in mass (weighed)

• liquids: weighed or volume recorded

  • density = mass/volume (units is g cm^-3)

• gases: mass or volume

• solutions: units is litre, dm³, cm³)

  • solute (dissolved substance) in is a known volume of solution (solute plus solvent)

Fixed mass of gas

• P = 1/ V

• P = T

• V = T

• Ideal gas equation: PV = nRT

  • R = 8.31 (J K-1 mol-1)

    

Unit 5: Molar volume of a gas

• ideal gas equation depends on the amount of gas but not on the nature of the gas

• one mole of any gas will occupy the same volume at the same temperature and pressure

• at 273K and 100kPa, the volume is 22.7 dm3

  

  Calculations from equations

  1. write down the correct formulas and all the reactants and products

  2. balance the equation

  3. work out the limiting reagent. the limiting reagent is the maximum yield to any of the products that can be determined

  4. work out the amount (in mol) of the substance

  5. convert to required unit

  6. express solution in the correct number of significant digits and units