Whats a Compound?
When two or more different elements are chemically joined together
What is an Ionic Compound?
- Its a compund that occurs between a metal and non metal
- Has very high melting and boiling points
- Conducts electricity when liquid or dissolved
- Dissolves in water
What is a covalent compound?
- It occurs between two non metals
- Low melting and boiling points
- cannot conduct electricity
- does not dissolve in water
How many electrons in each shell?
2 in the first shell
8 in the second shell
8 in the third shell
What is an ion?
An ion is any atom with a charge
Whats an Ionic structure?
- Compounds containing ionic bonds have giant ionic structures
- They contain millions of ions bonded together to form a crystal
- The ions are strongly attached together
- They have high melting and boiling point and are very hard.
Whats a Covalent Structures?
- They are called simple covalent structures
- The bonds between each molecule are weak
- They have low melting and boiling points
- They do not contain ions and cannot conduct electricity
Whats a Diamond? How is it important?
- Made up of carbon atoms covalently bonded together
- Each carbon atom is attached to 4 others
- Has high melting and boiling points
- Many strong interlocking bonds making it very strong
- Diamonds do not conduct electricity
- used in jewellery or cutting tools
Whats Graphite? How is it important?
- Contains layers of carbon atoms covalently bonded together
- Bonds to 3 other carbon atoms in a hexagon shape
- Carbon atoms are attached together to one another by weak forces that can easily be overcome
- high melting and boiling points
- Strong interlocking bonds
- Graphite is soft and easily broken.
- Conducts electricity as each carbon atom has 1 free electron that is able to move about and carry electricty
- Cannot dissolve in wate
- Put in pensils and lubricants
Whats a metal bond?
A metal bond is a pure metal with thousands of metal atoms very close together in a giant structure.
What do the free electrons do in a metal bond?
- hold the atom together in a reular structure giving the metal a fixed shape and volume
- It allows the atoms to slide over one another, making them ductile and malleable
- Allows the metal to conduct eletrictity and heat as the electrons are free to move and carry electricity
Whats a Smart Material?
A smart material is a material that can reversibly change its properties in response to changes in its surroundings
E.g Temperature, Light and pH
Whats Thermochromic Pigments?
Its a smart material that changes colour with changes in temperature
- strip thermometers
- cups for hot drinks
- battery power indicators
- warning signs
Whats Photochromic Pigment?
It changes colour with changing in light intensity
- Glasses that change colour in the light
Whats a shape memory alloy?
Its a smart material that regains its original shape when its heated
- Coffee pots
- Surgical plates
Whats a shape memory polymer?
Its a smart material that regains its shape when heated (Its a plastic not mixtures of metals)
Could potentially be used for car bodies
Whats Polymer gel? ( Hydrogels )
A polymer gel can absorb or expel huge volumes of water. It swells up to 1000 times its own volume due to the change in pH and temperatures
Used in magic snow and nappies