Simple Molecular Substances, Polymers, Giant Covalent Structures Flashcards
(25 cards)
What are simple molecular substances?
Substances made of molecules held together by covalent bonds, with weak intermolecular forces between molecules.
Why do simple molecular substances have low melting and boiling points?
Because only weak intermolecular forces need to be overcome, not the covalent bonds.
Do simple molecular substances conduct electricity?
No, because they do not have free electrons or ions.
Give an example of a simple molecular substance.
Water (H₂O), carbon dioxide (CO₂), oxygen (O2)
What type of bond holds atoms together within a molecule?
Covalent bond.
What type of bond holds separate molecules together?
Intermolecular forces
How does molecule size affect boiling point?
Larger molecules have stronger intermolecular forces, so higher boiling points.
Are simple molecular substances soluble in water?
Some are, depending on whether they can form hydrogen bonds with water.
What is a polymer?
A large molecule made from many repeating small units called monomers.
How are polymers formed?
By polymerisation, where monomers join together in a chemical reaction.
What is an addition polymer?
A polymer made from alkene monomers by addition reactions.
Give an example of an addition polymer.
Poly(ethene), made from ethene.
Why do polymers have higher melting points than simple molecules?
Because they have larger molecules with stronger intermolecular forces.
Are most polymers good conductors of electricity?
No, because they do not have free electrons or ions.
How can you identify a polymers repeating unit?
A segment shown in brackets with a subscript n and bond going through each bracket
What is a monomer?
A small molecule that can join with others to form a polymer.
What is a giant covalent structure?
A substance with a huge network of covalently bonded atoms.
Give two examples of giant covalent substances.
Diamond and graphite.
Why does diamond have a high melting point?
Because all atoms are held in place by strong covalent bonds that require lots of energy to break.
Why is diamond hard?
Each carbon atom is bonded to four others in a rigid 3D structure.
Why does graphite conduct electricity?
It has delocalised electrons that can move between layers.
Why is graphite soft and slippery?
Layers of atoms can slide over each other due to weak forces between layers.
What is graphene?
A single layer of graphite, one atom thick, with excellent electrical conductivity.
What is silicon dioxide?
A giant covalent structure found in sand, made of silicon and oxygen.
