states of matter

• The gas contains a large number of molecules moving in random directions at random speeds. • Electrostatic forces between molecules is negligible, except during collisions. • Collisions are perfectly elastic. • Time of collisions between molecules is negligible compared to time between collisions. • The molecules of a gas occupy negligible volume compared to the total volume of the gas.

• The gas contains a large number of molecules moving in random directions at random speeds. • Electrostatic forces between molecules is negligible, except during collisions. • Collisions are perfectly elastic. • Time of collisions between molecules is negligible compared to time between collisions. • The molecules of a gas occupy negligible volume compared to the total volume of the gas.

● Low pressure ● High temperature

● Intermolecular forces are no longer negligible and have to be considered. ● Molecular size is also no longer negligible and has to be considered.

pV = nRT p - pressure (Pa) V - volume (m3) n - number of moles (mol) R - gas constant (8.314 J K-1 mol-1) T - temperature (K)

M = m/n M - molecular mass n - number of moles (mol) m - mass (g)

● Particles are close together but not regularly arranged. ● Particles have a little more kinetic energy than in a solid. ● There are fewer electrostatic forces between particles than in a solid, allowing particles to move past each other and flow.

● Solid → Liquid ● Increasing the temperature of the surroundings causes particles to absorb energy meaning they gain more kinetic energy. ● Eventually, the particles gain enough energy to disrupt the regular arrangement and become a liquid.

● Liquid → Gas ● Heat energy causes particles in a liquid to move fast enough to break all forces of attraction between them and become a gas.

When a liquid evaporates in a closed container, the gaseous particles move around above the liquid. When these particles collide with the walls of the container, they exert a pressure called the vapour pressure.

● Regular, repeating arrangement (lattice). ● Caused by the electrostatic attraction between the oppositely charged ions.

● Iodine is an example of a simple molecular lattice. ● Iodine, I2 molecules form a larger structure due to intermolecular forces (Van der Waals Forces) between molecules. ● The structure is described as face centred cubic.

Allotropes are different physical forms of an element in the same state.

Lattice structure E.g. a buckminsterfullerene (C60) is a molecule consisting of 60 carbon atoms arranged in pentagons and hexagons.

A graphene sheet rolled up into a tube (single sheet of carbon atoms covalently bonded together)

● Giant covalent lattice. ● Each carbon atom is covalently bonded to four other carbon atoms. ● Extremely strong structure. ● Bond shape and angle around each carbon: Tetrahedral, 109.5°.

● Giant covalent lattice. ● Made from layers of carbon arranged in hexagonal rings. ● There are weak london forces between layers. ● Each carbon atom bonds covalently to 3 other carbon atoms. ● One delocalised electron per carbon.

● Giant covalent lattice. ● Single layer of graphite. ● Each carbon atom is bonded to 3 other carbon atoms to create a hexagonal ringed structure. ● One delocalised electron per carbon.

Describe the structure of silicon(IV) oxide ● Similar 3D structure to diamond. ● Silicon and oxygen atoms covalently bonded together.

Describe the structure of ice ● Open lattice structure. ● Hydrogen bonds hold water molecules apart in hexagonal rings.

Giant metallic lattice with positive ions packed closely together with delocalised electrons. In copper, each atom is surrounded by 12 other copper atoms.

● Positive charges = ions ● Negative charges = electrons

A resource that is used up faster than it is replaced. This resource will run out if it is continually used.

● To conserve finite resources for as long as possible by reducing the rate at which the are used. ● Reduces greenhouse gas emissions (which cause global warming). ● May reduce costs and other environmental impacts of a material.