Unit 2: 2 - Structure and Properties Flashcards
Can ionic compounds conduct electricity in solid state?
No, only in liquid form.
Why do ionic solids have high melting points?
They have very strong electrostatic forces of attraction in ionic bonds so this holds them together.
Why can ionic compounds which are molten or in a solution conduct electricity?
As the ions can move around, they can carry electrical charge.
What are intermolecular forces?
Intermolecular forces are very weak forces of attraction between molecules. These forces are overcome when a molecular substance melts or boils.
What is the general rule for the size of intermolecular forces?
The bigger the molecule, the bigger the forces. Small molecules like H2 have the weakest intermolecular substances so are gas at room temperature. The bigger molecules like C6H14 have stronger forces of attraction so may be liquid at room temperature.
What is another name for giant covalent structures?
Macromolecules
What is a major property of a giant covalent structure and why?
High melting/boiling point. As every atom is joined to multiple other atoms (e.g. In diamond) it is very hard to separate all these forces therefore it takes a lot of energy.
Why is diamond so hard?
Every carbon atom is covalently bonded to 4 others in a 3D structure, making it hard and transparent.
Why does graphite conduct electricity (and heat)?
When carbon atoms covalently bond with each other an electron is delocalised. This can carry electrical energy.
Why is graphite slippery and grey?
Carbon atoms in graphite are joined to 3 others in a 2D structure, forming layers which slide over each other.
What are fullerenes made of?
Carbon
How are fullerenes arranged?
They are large molecules made with hexagonal rings of carbon atoms. The rings join together to make cage-like shapes, some of which are nano-sized.
Name 3 uses of fullerenes
Drug delivery into the body, lubricants and catalysts (also reinforcing materials).
Why are pure metals malleable?
The atoms can easily slide over each other without breaking allowing them to form a new shape.
What uses do malleable metals have?
Wires, rods, sheets, tin foil etc.
What is an alloy?
An alloy is a mixture of metals or a metal mixed with other elements.
Why can alloys be more useful than pure metals?
Alloys distort the layers so therefore can make them harder (e.g. Steel is harder than iron). Also, they can be harder to corrode, and shape memory alloys will revert to their original shape after being heated, and therefore are useful in things like dental braces.
Why are metals good conductors?
Metal lattices have lots of delocalised electrons which carry electric charge.
What is a thermosoftening polymer?
A polymer that melts or softens easily when heated.
What is a thermosetting polymer?
A polymer which does not melt or soften when heated.
Why does high density and low density poly(ethene) have different properties?
High density and low density poly(ethene) were made under different conditions and with different catalysts, so therefore HD has a higher melting point and is stronger than LD.
Give an example of a thermosoftening polymer
Poly(ethene)
Give the molecular structures of thermosoftening polymers
In thermosoftening polymers, the polymer chains are tangled together, so when heated they fall apart from each other and are easily moved, as the intermolecular forces are weak.
Give the molecular structures of thermosetting polymers
When formed, thermosetting polymers form cross-like links with each other and form covalent bonds, which are hard to break.
