C2

• The three states of matter are solid, liquid, and gas
• For a substance to change state, energy must be transferred
• Particles gain energy during state changes, breaking attractive forces between them
• Evaporation and boiling require different amounts of energy to overcome chemical bonds between particles
• In evaporation, particles leave the liquid surface; in boiling, bubbles form throughout the liquid
• The energy needed for a substance to change state depends on the strength of attractive forces between particles
• Substances with strong attractive forces have higher melting and boiling points
• Solids have particles in a regular pattern, vibrate in a fixed position, and are tightly packed with low kinetic energy
• Liquids have randomly arranged particles that can move around each other with greater kinetic energy than solids
• Gases have randomly arranged particles that move quickly in all directions with the highest kinetic energy among states of matter
• Gases can be compressed as particles have space to move into
• The limitations of the Particle Model include not representing chemical bonds, particles not being solid spheres, and particles not always being spherical
• Identifying the physical state of a substance depends on its temperature relative to melting and boiling points
• State symbols in chemical equations: solid (s), liquid (l), gas (g), aqueous (aq)
• Ions are charged particles formed when elements lose or gain electrons
• Metals lose electrons to become positively charged ions, while non-metals gain electrons to become negatively charged ions
• Metallic bonding involves positive metal ions surrounded by delocalised electrons, creating strong electrostatic forces of attraction
• Alloys are mixtures of metals that prevent layers from sliding over each other, making them harder than pure metals
• Metals are strong, shiny, malleable, and good conductors; non-metals are brittle, dull, and poor conductors
• Ionic bonding occurs between a metal and a non-metal, forming ionic compounds with giant lattices
• Ionic compounds have high melting and boiling points, cannot conduct electricity in a solid state, but can when molten or in solution
• Covalent bonding involves the sharing of electron pairs between non-metals to achieve a full outer shell
• Covalent bonding involves the sharing of a pair of electrons between atoms to achieve a full outer shell
• Covalent bonding occurs between non-metals only
• Simple covalent structures have low melting and boiling points due to weak intermolecular forces that break when heated, not the strong covalent bonds between atoms
• Simple covalent structures do not conduct electricity as they lack free delocalised electrons
• Dot and cross diagrams are useful to show the bonding in simple molecules
• Dot and cross diagrams represent the outer electron shell of each atom as a circle, with overlapping circles to show covalent bonds and electrons represented as dots or crosses
• Structural formulae use the element symbol to represent the type of atom and a straight line to represent the covalent bonding between atoms
• Giant covalent structures include diamond, graphite, and graphene
• Nanoscience refers to structures that are 1–100nm in size, with nanoparticles having a high surface area to volume ratio
• Polymers are long chain molecules made up of monomers, with strong covalent bonds within the polymer chain and intermolecular forces between polymer molecules
• Fullerenes and nanotubes have various applications and properties, including conducting electricity and strengthening materials
• Possible risks of nanoparticles include inhalation, harmful reactions in the body, and binding of toxic substances due to their large surface area to volume ratio