Easy summary for States of matter a level chemistry

Easy summary for States of matter a level chemistry. Preparing for Gce

Learning outcomes You should be able to: ■

■ state the basic assumptions of the kinetic theory as applied to an ideal gas ■

■ explain qualitatively in terms of intermolecular forces and molecular size: – the conditions necessary for a gas to approach ideal behaviour – the limitations of ideality at very high pressures and very low temperatures ■

■ state and use the general gas equation pV = nRT in calculations, including the determination of Mr ■

■ describe, using a kinetic-molecular model, the liquid state, melting, vaporisation and vapour pressure ■

■ describe in simple terms the lattice structures of crystalline solids, including those that are ionic, simple molecular (as in iodine and the fullerene allotropes of carbon), giant molecular (as in silicon(IV) oxide and the graphite, diamond and graphene allotropes of carbon), hydrogen bonded or metallic ■

■ discuss the finite nature of materials as a resource and the importance of recycling processes ■

■ outline the importance of hydrogen bonding to the physical properties of substances, including ice and water ■

■ suggest from quoted physical data the type of structure and bonding present in a substance

Summary  for states of matter■

 The kinetic theory of gases states that gas particles are always in constant random motion at a variety of speeds. 

■ The volume of a gas increases when the temperature increases and decreases when the pressure increases. 

■ The volume of a gas under different conditions of temperature and pressure can be calculated using the ideal gas equation pV = nRT. 

■ The ideal gas equation can be used to determine the relative molecular mass of simple molecules. 

■ Gases do not obey the ideal gas equation at low temperatures and high pressures. 

■ The kinetic-molecular model can be used to describe the states of matter in terms of proximity and motion of the particles, and to describe changes of state and vapour pressure. 

■ Ionic compounds such as sodium chloride and magnesium oxide form a giant three-dimensional lattice structure containing ions in a regularly repeating pattern. 

■ The strong ionic forces acting in all directions between the ions in the lattice cause ionic substances to have high melting and boiling points.

■ Simple molecular solids with low melting points such as iodine have a regular arrangement of molecules; they are crystalline. There are weak intermolecular forces between the molecules.

■ Giant covalent (giant molecular) structures such as diamond have a large number of covalent bonds arranged in a regularly repeating pattern.

■ Fullerenes are allotropes of carbon in the shape of hollow spheres (buckminsterfullerene) or tubes (nanotubes).

■ Graphene is composed of a single flat sheet of hexagonally-arranged carbon atoms.

■ The strong covalent bonds between the atoms in giant molecular structures cause these substances to have high melting and boiling points.

■ In metals, the atoms are closely packed in a giant lattice in which the outer electrons are free to move.

■ Metals such as aluminium and copper and their alloys have a variety of uses, which can be related to their physical properties, e.g. density, malleability, conductivity, hardness.

■ Physical data can be used to suggest the type of structure and bonding present in a substance.

■ Recycling plays an important part in conserving finite resources such as metals.