C2.2 How structure influences the properties and uses of substances Flashcards
What are substances that consist of simple molecules?
Gases, liquids or solids that have relatively low melting and boiling points
What forces do substances that consist of simple molecules have between the molecules?
Weak intermolecular forces
Which forces are overcome in a simple molecular substance?
The intermolecular forces, not the covalent bonds
Why do substances that consist of simple molecules not conduct electricity?
They do not have an overall electric charge
What are some examples of substances that consist of simple molecules?
Chlorine, oxygen and water
What structures do Ionic compounds have?
Regular structures, Giant Ionic Lattices
What do Giant ionic lattices have?
Strong electrostatic forces in all directions between oppositely charged ions
Why do ionic compounds have high melting and boiling points?
Because large amounts of energy are needed to break the many strong bonds
When do ionic compounds conduct electricity and why?
When melted or dissolved in water because the ions are free to move and carry the current
What can atoms that share electrons also form aside form simple molecular substances?
Giant covalent structures / macromolecules
What are some example of giant covalent structures (lattices)?
Diamond, silicon dioxide and graphite
How are atoms linked in giant covalent structures?
By strong covalent bonds
What do the strong covalent bonds in giant covalent structures result in them having?
Very high melting and boiling points
In diamond, how many covalent bonds does each carbon atom form?
Four, so diamond is very hard
In graphite, how many covalent bonds does each carbon atom form?
Three, forming layers
Why is graphite soft and slippery?
There are no covalent bonds between the layers so they are free to slide over each other
Why can the layers of graphite be rubbed off so easily?
There are weak intermolecular forces between the layers
Why is graphite a good conductor of heat and electricity?
Because each carbon atom has a delocalised electron which can move freely through the structure carrying the current, allowing graphite to conduct heat and electricity
What else can carbon atoms form?
Fullerenes with different numbers of carbon atoms
What is the structure of fullerenes?
Hexagonal rings of carbon atoms
What can fullerenes be used for?
Drug delivery into the body, in lubricants, as catalysts, and in nanotubes for reinforcing materials e.g. in tennis rackets
Why do metals conduct heat and electricity?
Because of their delocalised electrons which are free to move around the whole structure
Why can metals be bent and shaped?
The layers in metals are free to slide over each other
What are alloys?
They are made up of two or more different metals
