End Of Unit Questions Flashcards
Why are compounds like methane and ammonia gases at room temperature?
They are made of small molecules or covalent bonds act only between the atoms within a molecule
Polymers made from different monomers have different properties. Why?
Different monomers change the structure of the polymer chains or the polymer chains have different shapes or structures
Some dental braces are made from shape memory alloys. What is meant by a shape memory alloy?
An alloy that can be deformed and changes back into its original shape when heated
Explain why diamonds are very hard
Every carbon atom is covalently bonded to four other carbon atoms in a giant 3D covalent structure
Why do ionic compounds need to be molten it in solution to conduct electricity?
The ions can’t move in the solid but become free to to move in the molten liquid or in solution
Explain why a block of copper can be hammered into a sheet.
The atoms are in layers which slide over each other into the new shape without breaking apart
Silver nanoparticles are used in some socks to help prevent bad smells. How are silver nanoparticles different from ordinary silver particles?
They are very much smaller and have a greater surface area
Silver nanoparticles are used in some socks to help prevent bad smells. Suggest why a sock manufacturer would use nanoparticles instead of ordinary silver particles
They are more effective because of their surface area, needs to use much less silver because it’s expensive, easier to attach to the sock fibres
Explain why thermosetting polymers are often used to make handles for cooking pans
They don’t soften or melt when they get hot, they are good insulators of heat, they can be moulded once but are then hard
Explain how the atoms in a metal are bonded to each other
The outer electrons delocalise leaving a lattice of positive ions, the delocalised electrons strongly attract the positive ions and hold them in place
Why can graphite conduct electricity?
There are delocalised electrons in graphite or one electron from each carbon atom is delocalised which carries the charge
Explain what is meant by intermolecular forces
Forces between molecules (much weaker than the covalent bonds between the molecules)
C60 is fullerene. What are fullerenes?
Forms of carbon with large molecules based on hexagonal rings of carbon atoms often cage like structures can be nanosized and have many useful applications
Why does it take a lot of energy to melt sodium chloride?
It has a giant ionic structure with strong electrostatic forces/bonds that hold the ions firmly in place and need a lot of energy to break them
