2 Structure and properties Flashcards
What is a lattice?
a 3D arrangement of particles in a giant structure
What is an ion?
a charged particle made when an atom loses or gains electrons
What is an ionic bond?
the electrostatic force of attraction between oppositely charged ions
Why do ionic compounds have high melting points?
because they have strong bonds which need lots of energy to break down
Why might ionic compounds conduct in a solution?
the ions can move freely in the solution, so they carry the charge, unlike in a solid where they don’t move
Why might ionic compounds be soluble in water?
the water breaks the bonds, but the ions don’t bond with the water
When do ionic compounds conduct electricity e.g. sodium chloride?
When they are part of a solution (with water) they conduct but not when they are solid
Which will conduct better in a solution- sodium chloride or magnesium oxide? Why?
Magnesium oxide
Requires 2 electrons to create ionic compound meaning there are stronger electrostatic forces- these don’t dissolve as easily so electricity conduction is weaker compared to sodium chloride which only loses 1 electron to make the ionic compound
What kind of melting and boiling points do substances with covalent bonds made up of simple molecules have?
Low
What are the covalent bonds like within the simple molecule?
Strong
What are the forces like between simple molecules?
Weak (why they have low melting and boiling points)
What charge do simple molecules have? Can they conduct electricity?
No overall charge therefore they can’t carry electrical charge- don’t conduct electricity
What are the forces called between atoms?
Intramolecular
What are the forces called between molecules?
Intermolecular
Why do ionic compounds only conduct electricity when they are dissolved in water?
their ions can freely move around and carry charge through the liquid
What are three examples of giant covalent structures made of carbon?
- diamond
- graphite
- buckminister fullurene (similar structure to a football)
What are the properties of diamond? (12)
- Giant lattice structure that continues in all directions
- Lustrous
- Very hard
- Colourless
- High melting point
- High boiling point
- Insoluble in water
- All its carbon atoms form 4 strong covalent bonds
- Doesn’t conduct electricity
- It is the hardest natural substance currently known
- Artificial diamonds can be made by heating pure carbon to very high temperatures under enormous pressure
- Industrial diamonds are used in drill bits of oil companies
What are the properties of graphite? (14)
- Relatively weak intermolecular forces between the layer so they can slide over each other easily
- Carbon atoms are arranged in hexagons
- Carbon atoms form 3 strong covalent bonds
- Each carbon atom has 1 spare electron
- The spare electron is free to move through the layers
- Feels slippery
- This spare electron allows graphite to conduct electricity
- Insoluble in water
- The spare atom is called a delocalised electron
- Lustrous
- Opaque
- Soft
- High melting point
- Conducts electricity
What are the properties of Fullerene? (8)
- Made of hexagonal rings of carbon atoms
- Describes any carbon structure which forms a cage-like structure
- Can conduct electricity as 1 electron has not formed a bond in each atom- these are free to move around and carry current
- Other molecules can be stored inside these cages which could potentially be used in medicine to transport drugs to a specific body part
- Insoluble in water
- 3 strong covalent bonds per atom
- Black solid
- Soluble in petrol (deep red solution)
What are they general properties of metals? (9)
- delocalised electrons
- good conductors of heat
- good conductors of electricity
- solid at room temperature (with the exception of mercury)
- malleable/ductile
- very dense
- shiny
- high melting/boiling points
- sonorous
Why are metals dense?
generally solid at room temperature meaning they have a regular lattice of layers - arranged particles
Why do metals have high melting/boiling points?
because the inter/intra molecular forces are strong meaning it takes more energy to break the bonds
Why do metals conduct heat/electricity?
the delocalised electrons can flow through the giant metallic lattice- the electrical current and heat are transferred quickly through the metal by free electrons
Why are metals malleable and ductile?
We can bend and shape metals because the layers of atoms (or ions) in a giant metallic structure can slide over each other
What are shape-memory alloys?
Metals which can be deformed into different shapes but upon heating will return to its original shape
What are examples of uses with shape-memory alloys?
- broken bones (cool alloy before it is shaped around the bone and when the body heats it up it pulls the bone with it back to its original shape)
- braces
NITINOL- made from nickel and titanium- successful but expensive
What affects the properties of polymers?
Monomers
Changing the reaction conditions
What are three examples of monomers and their properties in polymers?
- poly(ethene) used for bottles and bags
- poly(propene) used for high density stronger items
- nylon (acid and base) used for clothing bags and other things
What is LDPE and how is it made?
Low density poly(ethene)
Made under very high pressure
In the presence of small amount of oxygen
Branded chains don’t pack close together
What HDPE and how is it made?
High density poly(ethene)
Made under slightly raised pressure
In the presence of a catalyst
Unbranched chains pack close together
What is the difference between LDPE and HDPE?
HDPE is stronger and has a higher softening temperature than LDPE
What are thermosetting polymers?
Able to soften and melt easily when heated
Tangled web of polymer chains
What are thermosetting polymers?
Strong covalent bonds between chains which form cross links
Will not soften but will char if heated very strongly
What is nanoscience?
The study of small particles which are between 1 and 100 nanometres in size
Why are nanoparticles being used?
They behave differently from the materials they are made from on a large scale however much as they are exciting there may be possible issues which arise from increased use
