C2 - Structure & Properties
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Why do ionic compounds conduct electricity when melted or dissolved in water?
Their ions can move freely and carry charge through the liquid.
Why do ionic compounds have high melting points?
It takes a lot of energy to break the many strong ionic bonds which hold the giant lattice together.
Which types of substances have low boiling points?
Substances made up of simple molecules.
Why do some substances have low boiling points?
The intermolecular forces between simple molecules are weak.
Why don’t simple molecules conduct electricity?
Simple molecules have no overall charge so cannot carry electrical charge.
What boiling points do giant covalent structures have?
High boiling points
Why is graphite soft and slippery?
• It contains layers of covalently bonded carbon atoms. • There are no covalent bonds between the layers. • The layers can slide over each other.
Why can graphite conduct electricity?
There are delocalised electrons along the layers.
What are fullerenes?
Large cage like structures based on hexagonal rings of carbon atoms.
Why does graphite have delocalised electrons?
Each carbon only forms three covalent bonds out of a possible four leaving a spare electron.
Give two possible uses of fullerenes.
• Delivering drugs to a specific part of the body. - Catalyst and lubricant
Why is it possible to bend and shape metals?
The layers of atoms/ions in a giant metallic structure can slide over each other.
Why do metals allow electricity and heat to pass through?
Delocalised electrons allow electricity and heat to pass through more easily.
What are shape memory alloys?
An alloy that, if deformed, can return to its original shape on heating.
Why are alloys harder than pure metals?
There are different sized atoms making it more difficult for the layers to slide.
What do the properties of a polymer depend on?
• The monomers used to make it. - The conditions of the reaction.
How is LDPE formed?
Ethene reacts under very high pressure and a trace of oxygen.
How is HDPE formed?
Using a catalyst at 50C and a slightly raised pressure.
What is a thermosoftening polymer?
A polymer that softens when heated and is made up of individual polymer chains tangled together.
What are thermosetting polymers?
Polymers which don’t melt when heated and have strong covalent bonds forming cross links between polymer chains.
What is nano science?
The study of small particles between 1and 100 nanometers in size.
Give seven possible uses of nano technology in the future.
• Self-cleaning glass • Modern sun screens • Cosmetics that are absorbed deeper into the skin. • Delivery of drugs in the body • Cancer treatment • Nano-tech electronics • Nanotechnology military suits
Explain how nano technology can be used in cancer treatment.
• Nano gold particles can be injected and absorbed by tumours. • Tumours have thin leaky blood vessels allowing the gold nano particles to enter without going into healthy cells. • A laser heats the gold which heats the tumour cells but not surrounding cells.
Give two disadvantages of using nanotechnology in medicine.
• They have a large surface area meaning a spark could trigger an explosion. • Nanoparticles could enter the bloodstream causing damage.