C2.2 Flashcards
What can’t simple molecules do?
Conduct electricity
The ions within a giant ionic lattice are held together by what?
Strong electrostatic forces
What are some features of ionic compounds?
~ High melting points
~ High boiling points
What is the name of the compound for salt?
Sodium chloride
What causes the high melting and boiling points in ionic compounds?
~ Strong electrostatic forces of attraction
~ Lots of energy is needed for the ions to break away from the forces of attraction
Why does silicon dioxide have high melting and boiling points?
Because of its strong covalent bonds
Why can graphite conduct heat and electricity?
~ Each carbon atom only forms 3 bonds with other carbon atoms
~ So each carbon atom has a delocalised electron which can pass on the electricity
How are the atoms in a metal arranged?
Neatly in rows
Why can a metal conduct heat and electricity?
It has delocalised electrons that are free to move and pass the electricity on
Why are all the atoms in a metal positively charged?
Because they’ve lost an electron, which is free to move
How are the positive ions and delocalised electrons held together in a metallic bond?
With strong electrostatic forces of attraction
Why are pure metals usually malleable?
~ They’re arranged in neat rows and columns
~ Layers can slide over each other
What does malleable mean?
Easily hammered or bent into shape
Why might alloys be made?
~ To change colour
~ To make metals much harder
What is the alloy nitinol made of?
Nickel and titanium
What are the properties of nitinol?
~ Shape can be changed when cooled
~ When heated it will go back into its original shape
Why is nitinol used as dental braces?
~ It can be cooled and wrapped around the teeth
~ The warmth of the mouth will cause the brace to try to get back to its original shape
~ This causes it to put pressure on the teeth and move them to a correct position
How is nitinol used to repair broken bones?
~ It’s cooled then wrapped around the bones
~ The body warmth will cause the nitinol to try to return to its original shape
~ This causes the nitinol to contract and hold the bones together as they repair
Why do metals have electrons that are free to move?
Because metals have electrons in the outer shell of the atoms that can move away from the atom, meaning they are delocalised
What does increasing the pressure do to polyethene?
Makes low density polyethene which has a lower melting point
What affects the density of polyethene?
The arrangement of the polymer chains, if they are closer together the forces of attraction between them will be stronger
What is a property of high density polyethene?
It has a high melting point
What are the forces of attraction like in low density polyethene?
Weaker because the polymers are further apart
What are properties of thermosoftening polymers?
Easily changed shape
What do thermosoftening polymers make?
Plastic bags
What are properties of thermosetting polymers?
Don’t change shape when heated
What bonds do thermosetting polymers have in them?
Strong covalent bonds which links the separate polymer chains
What do thermosetting polymers make?
~ Plugs
~ Cooking spatulas
~ Panhandles
Why are thermosoftening polymers easy to separate?
~ Weak intermolecular forces of attraction
~ Polymers can separate more easily at lower temperatures
~ Less heat energy is needed to separate the polymer chains
Why can’t simple molecules conduct electricity?
Because the molecules have no overall charge
What may nanoparticles lead to the development of?
~ New computers
~ New catalysts
~ New cosmetics
What does sonorous mean?
Metals ring like a bell when hit, not a dull thud
What does ductile mean?
Metals can be drawn into wires
What does lustrous mean?
All metals are shiny when polished or cut
What is the test for carbon dioxide?
Makes a lit splint go out, or makes limewater go cloudy
What is a displacement reaction?
When a less reactive metal reacts with a more reactive metal solution, so the solution displaces the solid and nothing really happens
