Name the 4 main structures that substances can have?
What sort of molecules do simple molecular substances have? And an example?
Small molecules eg H2O
SIMPLE MOLECULAR: What are the atoms in the molecules held together by? And what forces are there between the molecules?
Atoms in molecules: Strong forces called covalent bonds
Molecules: Very weak forces
What are the properties of Simple Molecular substances?
Low melting and boiling points
- Tend to be soft and/or have little strength
- Do not conduct electricity
What sort of elements are simple molecular substances?
Giant Covalent Substances: How are the giant structures made?
Strong covalent bonds join atoms together in large numbers to make giant structures
Giant Covalent Substances: Give 2 examples
Diamond and graphite
Giant Covalent Substances: Strength of bonds?
Giant Covalent Substances: Properties?
- Very high melting points
- Very hard (except graphite)
Don't conduct electricity (except graphite)
Insoluble in all solvents
- Insoluble in all solvents
Giant Metallic Structures: What is the structure of the atoms in metals?
The atoms in metals are in layers which can slide over each other, this makes it possible to bend them or beat them into shape
Giant Metallic Structures: Properties?
- Metals are strong
- Metals have high melting points
- Metals are malleable
- Metals are good conductors of electricity and heat
- Metals are listrous (shiny)
ALL BECAUSE THEY HAVE STRONG BONDS
Giant Ionic Structures: What are they made up of?
Made up of positive metal ions and negative non-metal ions
Giant Ionic Structures: What are they arrange like?
In a regular lattice so that each positive ions is surrounded by a negative ion and vise versa
The particles are held together by the strong attraction of positive for negative
Giant Ionic Structures: Properties?
- High melting and boiling points
- Hard but brittle
- Conduct electricity only when melted or dissolved in water
- Many ionic substances are soluble in water
What are alloys?
Mixtures of metals
Why are alloys made?
Additional elements are added to improve the properties of the metal
In terms of atom size, why are alloys stronger than the origional?
In an alloy, the atoms have different sizes this means they can no longer slide so easily. This makes the alloy harder and stronger than the origional material
What are nanoparticles?
Smal particles measuring 1-100 nanometers
1nm = 0.000 000 001
What are nanotubes?
Fullerenes (molecules of carbon) joined together, hollow carbon tubes
Why are nanotubes strong?
Because of the covalent bonds
Give some uses of nanotubes in nanoscience
- Can be used to make stronger, lighter building materials
- New cosmetics that don't leave white marks
- Can be used in tiny electrical circuits for computer chips
What determines the properties of plastic?
The bonds between the different molecule chains
What affects the properties of polymers?
The starting materials and reaction conditions